Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!





Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

Did you get a great deal? Let us know in the Values & Prices Paid section!
Meet your fellow owners in our Owners Clubs

Hemi's: any make, any size....What do you think?

smokin_olds442smokin_olds442 Posts: 41
edited March 2014 in Chrysler
I've seen many hemi's and hemi-like engines in my time, some good and some bad. I'd like to know what everyone else in the muscle car realm has to say about it, good or bad. Personally I'm a big hemi fan. The only thing about hemi's is that they have less low end torque than a swirl or quench type combustion chamber type engine...but a little more top end horsepower. I guess it's a little bit of give and take.
«1

Comments

  • andre1969andre1969 Posts: 23,571
    ...is the 341-2bbl that's under the hood of my '57 DeSoto. Now it's not exactly a high-performance setup; it's rated at 270 hp gross. But still, it has no trouble getting two tons of DeSoto moving, and it actually performs better and gets better fuel economy than some lighter cars with smaller engines that I've owned. For example, I've had three cars with 318's...a '68 Dart, a '79 Newport, and an '89 Gran Fury. In around-town driving, the DeSoto gets slightly better fuel economy than any of them, and only the Dart is quicker from 0-60.

    One reason I've heard that Hemi-powered DeSotos and Chryslers from this era are fairly rare is that people would buy them for the engine, junk the body, and then throw the engine into something else and use it for drag racing. Of course, the build quality on the '57's also ensured that they'd get junked a little prematurely :-(
  • moparmadmoparmad Posts: 197
    Nothing is more beautiful...any size,any make.
    I don't know if a Hemi inherently lacks torque or if they just seem to because they were nearly always built for maximum performance,and maximizing horsepower always hurts low end torque.
  • andre1969andre1969 Posts: 23,571
    I could see the 426 Hemi possibly hurting a bit for low-end torque, since it was designed to be a race car engine that was barely streetable. Still, didn't the '68 Dart Hemi hold some kind of speed record that still stands today?


    I know when the Hemi first came out in the early 50's, its main advantages were more horsepower at a lower compression. Way back when, there was no high octane gasoline, so they could only make compression ratios so high. I know in the example of DeSoto's first Hemi, the 276.1, it had 160 hp. In comparison, I think Oldsmobile needed an engine of around 330 CID to get the same hp.


    All that changed by aroud '55, as high HP engines started popping up everywhere, and the Chrysler 300 became the first American production car to break the 300 hp barrier. The next year, it broke the 1 hp per cubic inch barrier, with an optional dual-quad 354 that pumped out 355 hp. It was also available with a wide array of axle ratios, on up to a 6.17:1 (IIRC). My old Chrysler history book notes that such a beast should do 0-60 in about 5 seconds, although I've never seen a road test to back that up.


    For anyone that's interested, here's a Hemi link... http://www.powerplayhemi.com/. It lists a lot of specs for all the early Chrysler Hemi and Poly engines. There are a few typo's though...for example, for the '57 DeSoto Firedome and Fireflite, they duplicate the hp figures in the torque column.


    The main thing that killed the early Hemi, I believe, were weight and mechanical complexity. A Chrysler 392 weighs 737 lb, and the DeSoto 330/341/345 weighed 669 lb. I don't think fuel economy or reliability was ever a concern, it's just that the corporate big-blocks that followed were just lighter and cheaper to build. And that's the bottom line, whether it's Chrysler, GM, Ford, or anybody. Cheaper always wins out.

  • I've heard a lot of talk about Chrysler hemi's but nobody talked about Fords hemi's. The 429SCJ(super cobra jet) had true hemispherical heads, while the 428 was called a "semi-hemi". And the reason for hemi's having lower torque is not because the way they were tuned but the shape of the combustion chamber. This hemi design burned much more of the air/fuel ratio and was not only more powerful but more efficient too, as said earlier by andre1969. These hemi engines had high volumetric efficiency but low BMEP(Brake Mean Effective Pressure) and that's why torque was low(in technical terms).
  • andre1969andre1969 Posts: 23,571
    ...but what about the 2.6 "Hemi" from Mitsubishi that Chrysler stuck in its K-cars for a few years? ;-) They even had the nerve to put a badge on the side of the car that said "2.6 Hemi". Does anybody know if that thing actually had hemispherical combustion chambers?

    Oh yeah, I never heard about the Ford 429 hemi...so it actually went into production? Didn't Oldsmobile build a prototype 455 with Hemi heads?
  • Well the 429 wasn't called a hemi as was chyrsler's 426, the 429 was known as the SCJ(super cobra jet) and had around 355bhp. The Mustang bodies they were put in had to be factory modified so that the wide 429SCJ could fit in the engine bay...wild!
  • modvptnlmodvptnl Posts: 1,352
    A few corrections if you don't mind. The Boss 429 was a Semi-Hemi head. It had a slight cresent shape in the combustion chamber. The CJ or SCJ NEVER had the Boss heads. There NEVER was a 428 semi-hemi. All 428's and most 427's were simple wedge heads. The SOHC 427 I'm not 100% sure on but it may have been closer to a hemi.

    Now the bad news. The Hemi is NOT an efficient design. It uses a domed combustion chamber in a parabolic shape and because of this can utilize very large valves which of course is great for high rpm horsepower but not the best for low rpm velocity. Because of this giant combustion chamber some weird piston shapes had to be made to get any compression. With valve notches and such, flame travel is compromised. Witness top fuel hemis, even with exotic fuels and big boost #'s they run 2 plugs per cylinder for ignition. Of course the hemi is a GREAT high RPM race engine but due to lower octane fuels, emissions and such it's not the most efficient design.

    Many people mistakingly think the current crop of 4 valve, centrally located spark plugs are hemis. Most of these heads are "pentproof" chambers which is a flater more efficient design.
  • if the plugs are centrally located in the chamber then yes it is a hemi-resembling design, and yes the hemi's were more efficient...they burn more of the fuel/air mixture than wedge heads and therefore have greater volumetric efficiency but low BMEP that is the reason why they have high rpm horsepower and not as much torque as the wedge design.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Please don't get personal in your posts ("you don't know what you're talkin' about, etc.")

    This is a very friendly board and we all ask for respect and courtesy. If you cant' follow these rules I may delete your posts whenever they resemble personal attacks.

    Mr. Shiftright
    Host
  • modvptnlmodvptnl Posts: 1,352
    What does "hemi resembling" mean?? Good try on back pedaling. A hemi is a HEMISPHERICAL true domed combustion chamber PERIOD. If it has any inturruptions in this parabolic chamber it is NOT A HEMI. The modular motors are WEDGE designed(except for the DOHC which is a pentproof chamber)Even though the plug comes in from the top of the SOHC the plug location is NO WHERE NEAR CENTRAL. The modulars have small bores and on the 2 valve heads a centrally located plug would be next to impossible. If you can, find a JULY isuue of MUSTANGS AND FAST FORDS. It shows a good picture of some 5.4, 2 valve heads off a Lightning. They are most obviuosly wedge chambers.
  • moparmadmoparmad Posts: 197
    The 426 crate Hemi makes 465 horsepower and 486 ft pounds of torque. From 3000 to 5000 rpm it never drops below 480 ft pounds,the chart doesn't give numbers below 3000 rpm but it doesn't appear to be dropping quickly below 3000.
    The proof of the pudding as far as the Hemi being ahead of its time is probably best reflected in the fact that here we are arguing about how efficient a 50 year old head design is. Obviously there is a little hype with the Hemi or Chrysler would have brought it back years ago,but just as obvious is the fact that even if it isn't that big of a help it certainly must not hurt either or it would remain dead.
    BTW... The latest numbers I've seen on the 5.7L Hemi for production are 330 horsepower and 375 ft pounds of torque!
  • modvptnlmodvptnl Posts: 1,352
    Yes the Hemi was an excellent head making tons of power but remember when this was!!!! 100 octane gas was .25 a gallon and there were no emissions to worry about. The "new" hemi I haven't seen yet. I will be VERY surprised if it's a TRUE hemispherical combustion chamber. Also realize that GM's LSI wedge head with relatively small bore is making more power than the "NEW" hemi and it's a 4 years old design. Ford's 5.4 with "modern" dohc 4 valve heads made 385 HP N/A. The hemi had it's day.......it's over now, sadly.

    BTW the Ford 514 crate motor makes 600 HP with good old "MODERN" wedge heads. Heck, the crate 392 stroker Ford motor out powers that hemi!!!
  • ndancendance Posts: 323
    Seems to me that the 'hemi' is mostly a marketing concept. Why anyone would care what the shape of the *combustion chamber* is, of all things, is beyond me. (My weary old memory banks seem to think that 426's idled really poorly, why?, poor camshaft design or an inefficient head design at low rpms?). With the amount of computer power available to modern mechanical engineers, I'll bet that they can cook up far more optimal designs than the kind of plug and pray techniques of the '50s and '60s. I'll also bet that killer port and chamber design result in shapes that are *not* obvious at first glance (just think of all the inserts built for heads (ZL1 for instance) which *shrink* the port size but actually increase flow).

    Kind of like assuming that smooth surfaces result in higher efficiency necessarily.
  • moparmadmoparmad Posts: 197
    The reason the 426 Hemi idled poorly had to do more with the cam than anything else. From the factory it had 284 degrees of duration and .490" lift on the intake and .481 lift on the exhaust,that is quite large for a street cam.
    The numbers I gave were for the first step Mopar Performance Hemi,the 528 Mopar Performance Hemi develops 610 horsepower and 650 ftlbs of torque,and it runs on 92 octane pump gas. If you include Ray Barton and other engine builders the power levels can go basically as high as you want to pay for. But this holds true of any engine doesn't it.
    As far as the new Hemi remember that these are numbers for the first incantation which is a truck engine and even though it doesn't put up the horsepower it delivers on the torque big time.
    I think the other misconception here is that the new Hemi is exactly the same as the old Hemi. I'm sure that it is a modernized version of the Hemi and is changed very much from what it once was. Also the flow of the head has more to do with the port design than the shape of the combustion chamber. One of the advantages of the Hemi head was that it lined up the head with the intake manifold better allowing a straighter shot for the port,this might seem like it would hurt the low speed velocity of the charge but remember that the ports can be tuned by varying their size and shape.
    The Hemi was banned by NASCAR which is what killed Fords Hemi,they no longer needed it to be competitive. It also killed the Chrysler DOHC Hemi which was in development to combat the Ford. The reason for the ban was simple. The Dodge and Plymouth aero-cars(Daytona and Superbird)were routinely breaking the 200 mph barrier,which given the limited knowledge of aerodynamics and the four wheel drum brakes was far from safe.
  • ndancendance Posts: 323
    I'm not sure that cam timing is the culprit.

    428 CJ specs:
    lift: i = .480, e = .490
    dur: i = 270, e = 290

    L72 spec:
    lift: i,e = .520
    dur: i = 316, e = 302

    (I'm assuming that duration was measured in a similar fashion, of course).

    428 CJ's (it *has* been a while, so maybe my memory is fogged) are really darned docile. Since I've only owned cars with the LS6, L89, and CJ motors, I can't really say how an L72 is to live with. I remember that magazine writers of the day (70/71) picked on the 426's for rough running. Now that I think of it, maybe the dual carb system is at fault, some sort of feedback loop with the idle circuits fighting with the distibutor advance fighting with the geometry of the gas flow through the engine.

    I admit, it drives me kind of crazy to use Grand National racing as any sort of metric on engine design. Although it is *real* racing, the sanctioning body (ie France) makes it impossible to really compare designs since they've cooked up 40 years of Mickey Mouse restrictions to keep the makes dead-even competitive.

    Now that the cars are 'stock' cars in name only (as compared to the '60s and before), they might as well drop all pretense and use real racing engines. Of course, all that would happen is Mercedes (or Porsche, or Honda, or ....) would show up, place their powerplant in some already dominant team's car, and win every race.
  • ndancendance Posts: 323
    that ultimate horsepower is largely a function of money more than of engine make (in terms of production based, US built, pushrod V8's). I'll bet that the prostock engine builders could start with practically any basic design (even Oldsmobile!) and build competitive horsepower levels. Of course, by that time they've redesigned a chunk of the oiling system, had their own heads machined from factory blanks or whatever, etc. etc. A nice example is the AMC engines used in the Trans-Am. Add Penske + Traco and, voila'. Instant race engine.

    I think that, in general, a 'good' high performance engine is one that a dummy like me can easily track down parts for, is reasonably priced, and I can understand. (The understand part is what keeps me away from 911's. . In terms of late '60s/ early '70s cars, it's real instructive to drive, say a Boss 302 on the same day as a '72 911S. They run about the same in a straight line, but the Mustang really is a POS in every other way).

    I suppose when you get right down to it, the optimal high-performance V8 available today (at least for lighter cars) is the Chevrolet ZZ4 crate engine. Really a smoking deal and pretty much unbeatable for the money. Slam that baby into a 914 (with the later gearbox of course) and you're livin' large.
  • mcsapmcsap Posts: 15
    It seems to me that Chrysler was the only company that took a racing engine and offered it as an option in production cars. There are a lot more 331/354/392/426 engines out there than any other "hemi" from any other company. I belive a minimum of 500 was required to be considered production back then.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Oh, hemis were quite common in Europe way before Chrysler but they were all I believe racing engines. Hemis in production cars prior to Chrysler would have to be Duesenberg and Stutz, and of course Miller and Offenhauser used this principle for racing. Chrysler's approach was different than the Euros or most racing cars because Chrysler did not use overhead cams, prefering the simpler idea of unequal length pushrods. It was a clever solution to keeping costs down, but of course without the overhead cams the engines didn't rev as high. But will all that displacement, high revs weren't necessary for the applications.
  • dustykdustyk Posts: 2,926
    ......usually contribute to increased torque. All other things being equal (bore, stroke, offset, camshaft timing, lift, duration, valve size) they produce more torque.

    Now, the 426 street hemi found in those "B" bodied Plymouth's and Dodge's of the 1960s felt a little weak on the take-off because of longer cam durations. When camshaft duration is increased above 270 degrees it'll have the same effect on any engine.

    Dusty
  • modvptnlmodvptnl Posts: 1,352
    I'll respectfully disagree. The MAIN advantage of a true Hemi is that you can use monstrous valve sizes because of the domed chamber. This and the HUGE ports afforded by the design will actually HURT torque, especially at lower revs because of the reduced port velocity.

    Of course, using forced induction and high rev horsepower the Hemi is still a valid design but the pentproof design used on modern 4 valve heads is a better all around design because of piston shape and a few other more favorable traits.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    I think ultimately an engine has to breath well and some hemis do and some don't. Also, the overwhelming factor in torque is displacement per cylinder.
  • modvptnlmodvptnl Posts: 1,352
    Case in point is why modern 4 valve heads have either varible valve or varible intake technology. These smaller displacement motors flow very near what the old hemis flowed with much less displacement. However, they would be absolute dogs if that amount of air were allowed in at lower RPM's. That's why air flow is limited til around 3,000 RPM on most of these multi valve motors.

    Will agree on the displacement comment......unless a motor has poor port velocity at lower RPM's.(HEMI)Regardless of what urban legend would have you believe the Hemi was a poor everyday street motor when compared to 440's, 460's and 454's. If it were more efficient and more torquey than a 440 at lower engine speeds, like required for large sedans, trucks, and even motorhomes it would have been simply de-tuned and run in place of the 440 wedge.

    Would like to add that bore/stroke ratio, rod ratio and of course valve timing all play parts in where a motor's powerband will be.
  • dustykdustyk Posts: 2,926
    .......If you read my comment carefully, I said all things being equal, including valve size. You are correct, hemispherical combustion chambers do allow the use of larger valves and when that feature of the design is taken advantage of low-end torque will most certainly suffer.

    Early hemis, such as the 331, did not use radical valve sizes or exceptionally long valve durations, yet produced more horsepower and low end torque than similar displacement engines from GM and Ford. This is especially true in the 180 and 250 HP versions, yet they produced high low-end torque.

    Look at Chrysler's new 353 Hemi and the low-end torque specs. I think you'll find that those numbers are not reachable in a true wedge combustion chamber design.

    Dusty
  • dustykdustyk Posts: 2,926
    >>Will agree on the displacement comment......unless a motor has poor port velocity at lower RPM's.(HEMI)Regardless of what urban legend would have you believe the Hemi was a poor everyday street motor when compared to 440's, 460's and 454's. If it were more efficient and more torquey than a 440 at lower engine speeds, like required for large sedans, trucks, and even motorhomes it would have been simply de-tuned and run in place of the 440 wedge. <<

    The Chrysler 426 (or for that matter, the 392) were not used in wide applications simply because of component and assembly manufacturing costs. In reality the Chrysler 426 hemi was one of the few -- if not only one -- of the period engines that produced more than the advertised horsepower and torque. In the mid-sixties I was a student at General Motors Institute - Tonowanda Engine School. I later was assigned to Buick. Anyway, they were testing a full bank of Chrysler 426 hemis (4, I think). The opinion was then that Chrysler was "cheating" with the 426. If my memory serves me correctly, they were able to record just below 500 horsepower in pure stock from. I believe in those days that would've been SAE net. We also did cost estimates on the 426. The component manufacturing costs were fairly easy to figure out (Chrysler was very conservative back then) and it was determined that Chrysler was actually selling the engine at cost when equipped in a car.

    As far as street driveability, I seem to recall that in '66 or '67 there was a spark plug heat range change which resolved most of the issues with streetability. It may be true that the 426 was never optimum, but I could say the same for 396 and early 350HP 327 Chevies, or 429 Canted valve Fords, just to name a few. A good friend of mine had a '70 Olds 442 which was just as troublesome as any engine I ever saw. Whether that was typical, I really don't know.

    The East Rochester, New York police department ran a couple of hemis for a number of years in '68 Satelite bodies and they had no problems with them.

    Dusty
  • speedshiftspeedshift Posts: 1,598
    Interesting stuff. I remember reading something in a magazine of the time that the first street hemi cam ('66-67) was in effect too torquey since lots of throttle just spun the tires. The later cam moved the torque peak up and made the engine's power more usable with the limited traction available from street tires in those days.

    As far as cost, the books usually say the hemi was replaced, first with the poly and then with the wedge because the hemis were more expensive to build. That's probably why they weren't more widely used within the Chrysler line-up.

    It's also generally accepted that it took more work to get a 426 hemi to reach its potential than the average wedge, although I suspect that had to do with the relatively high state of tune it came in. The performance numbers of a non-breathed upon hemi are pretty ordinary, although the potential was certainly there. It was one of the more radical engines of the late '60s, almost a throwback to the dual quad 409s and Ford 427s of the early '60s.

    I remember reading something about the hemi being more prone to detonation because it doesn't have a quench area.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    WEll, you know, if you combine the concepts of over 400 CID, carburetors, a stiff clutch, and very high compression, no car equipped like that is going to drive very well on the street. And add to that the monstrous size of these cars, and you realize that these are not commuter cars!

    This is why I sometimes advise "dreamers" who want a 60s "muscle car" to pick a tamer V8 with an automatic and a drop-top. It's not quite the same fantasy as hell's bells tire-smoking power, but you have a car you can use everyday.
  • modvptnlmodvptnl Posts: 1,352
    I knew the "expensive to produce" card would rear its head. the ONLY reason that may have been is simply due to lack of MASS production. The costs would come down considerably if the numbers went up.

    The comment about the up-coming "Hemi" is very misleading.

    1) I will only believe it's a hemi when I see a chamber. At this time I believe it to be a marketing ploy. The funny thing is it's called a "Hemi Magnum. Isn't that an oxymoron if you're a Chrysler fan.

    2) I've seen figures of 365 pounds of torque from a 5.7L"hemi" The current VERY MILD wedge head 5.4L Fords have 355 pounds of torque. The LS1 chevys are in the vette are higher. Advantage hemi?????

    Your 429 canted valve head comment makes no sense to me. It's the same canted valve head as the 460. a very streetable motor.

    The hemi in its pure form is a great high revving forced induction design that can move a LOT of air. The parabolic domed chamber leads to a very poor domed piston design for both flame travel and control of emissions. It is not a good low RPM/emissions street motor.

    The comparison of "early hemis" with small valves means nothing to me. There absolutely is no advantage to the domed chamber if not utilizing the generous valve space. If they had more power it would have been a simple matter of a higher state of tune(compression/cam etc) not because a domed chamber magically makes more power.

    In 2 very recent HOT ROD comparisons they ran a wedge vs. Hemi in a big Chrysler sedan. The hemi won by a few tenths. The overall consensus was that in the sate of tune to do that they'd rather have the wedge as an everyday car.

    In a Buick 455GN vs. hemi shootout the hemi fell on it's face. the Buicks cleaned up. Again it was stated in this street state of tune the greater low end torque of the very mundane Buicks kicked butt.
  • dustykdustyk Posts: 2,926
    On one hand you wish to discount the horsepower/torque capabilities of early hemis because of "state of tune," yet the same rule must apply to your comparisons as well.

    Yes, I believe the hemispherical combustion chamber does not lend itself as nicely as a wedge to emissions applications, but I don't believe these problems are insurmountable. The hemi-head offers a benefit in increased combustion efficiency, especially at higher flow rates.

    The article I read on the new 353 Hemi said they are using two spark plugs per cylinder. The advertised torque rating is 300 lbs at 1000 RPM, 325 lbs at 1500 rpm, and 360 pound feet at 4000 rpm. I don't know how that compares to the 5.4 Ford, but maybe its a different state of tune.

    As I stated earlier, my comment was based on "all other things being equal."
  • modvptnlmodvptnl Posts: 1,352
    I construed your first comment that I commented on as you saying the hemi lends it self to more low end torque because it's a hemi. I stand by the fact that what makes a hemi advantageous at higher RPM's hurts its low speed torque ability. you can't have it both ways. just as open exhaust helps at higher RPM's, it will hurt the torque down low. Too much air flow is a liability at lower engine speeds.

    I will believe the new hemi has real hemispherical heads when I see them. As I stated, the MILD 5.4 OHC Ford makes 355 pounds, I believe it's at a lower 3200 RPM.

    Much like my feelings about DOHC 4 valve technology, a real Hemi head is not being utilized in a low RPM smog motor.
  • speedshiftspeedshift Posts: 1,598
    The 426 hemi was expensive in part because of low production and in part because it was a detuned racing engine with HD parts.

    However, the evidence suggests that the early hemi was relatively expensive to produce even as a regular production engine. Every 1951-54 V8-powered Chrysler, De Soto or Dodge had a hemi, so in the early days they had economies of scale. But by 1955 the polysphere had replaced the hemi in the cheaper Dodges and Chryslers and was standard in the Plymouth and Dodge trucks. By 1959 the wedge had completely replaced the hemi--the Dodge hemi had lasted only five years. Since Chrysler didn't replace the hemi that quickly because it didn't perform, the conclusion is that it was more expensive to make than the wedge. If nothing else, the fact that the hemi weighed 100 pounds more than the wedge means it took more cast iron to make.
  • andre1969andre1969 Posts: 23,571
    ...how did the more generic Hemis compare to the later wedge-head engines? For example, the 341 2bbl hemi in my '57 DeSoto is rated at 270 hp, although I forget the torque. I had a '67 Newport a few years ago, with a 383 2-bbl. I'm not sure, but I think it only had 270 hp as well, despite having an extra 42 cubes.

    Any ideas on, theoretically, which one would win a stoplight race?
  • dustykdustyk Posts: 2,926
    "Hemispherical combustion chambers usually contribute to increased torque. All other things being equal (bore, stroke, offset, camshaft timing, lift, duration, valve size) they produce more torque."

    What I did not say was they would produce a torque curve identical to a wedge combustion chamber - all other things being equal. And I never stated in an unqualified manner that they would always produce more torque at any given RPM. There are a number of variables that contribute to the horsepower and torque characteristics of a reciprocating internal combustion engine. Forget cylinder head design, compression ratio, I could drastically change both the horsepower AND torque curves just by altering the weight of the flywheel!

    You seem to be legend-stuck into thinking that every "hemi" must be like the Chrysler 426 offered to civilians. Chrysler's earlier versions were not anywhere near as radical. Yes, I agree with you that "too much air flow is a liability at lower engine speeds." But you are apparently thinking that every hemi ever made had higher flow rates. That's simply not true.

    Your comment that all Chrysler had to do was make the "hemi" in mass production is incorrect. Are you assuming that all 426 hemis were hand built? Just a guess, but I suspect - just like every other manufacture's hi-po motors - that production numbers were pretty low. I'd be surprised if they were more than 5000 units in any given year, but using that figure it's hard to amortise manufacturing machinery, floor space, and labor at rates that low. For any manufacturer. Yes, you can amortise making more units, but even if they made them was Chrysler going to sell 50,000 426 hemis a year? I don't think so.

    I'm no hemi authority by any means, but I remember seeing them apart at Tonowanda Engine Plant. The block wasn't a biggie, but there was a lot of machining in those heads as I recall. Worse yet, all of those angular cuts had to be made at one station to ensure that the head remained indexed during all of those operations. That's not the way its done on production wedges, I can tell you that.

    Your comment about hemis being prone to detonation just didn't make any sense to me. I admittedly had to consult with a few more knowledgeable "hemi" people then myself. By the design itself a hemispherical combustion chamber is not more detonation prone. It is true that the hemi head (in the Chrysler's executed manner, at least) does come up to peak CR at a faster rate then most wedge chambers using flat-top pistons. But so do engines that utilize a domed piston in a wedge chamber. That's no real surprise and its exacerbated in any engine that has limited "squish" area. But this issue is moot if the engine is timed correctly and the correct octane is maintained.

    My only hemi-head (as in person, this time) source tells me that 426 hemis of the period were not detonation prone. However, driveway tuners would occasionally try to kick some basic timing advance in on them, and yes, they'd detonate. But my trusted source says that timed "at the mark" they were no more prone to this than any other engine sporting compression ratios over 10:1.

    Your "state of tune" comment made me do some investigating. I remember the 429 canted-valve engines to be a bit punky on the street. I looked at my 1971 Engine Data Book. Here are some pertinent facts:

    Chysler 426 "hemi"
    425 hp @ 5000 rpm
    490 lbs @ 4000 rpm
    valve lift .490 / .481
    duration 284 degrees, 60 degree overlap, CR 10.2

    Ford 429 Cobra Jet
    375 hp @ 5400 rpm
    450 lbs @ 3400
    valve lift .515 / .515
    duration 300 degrees, 72 degree overlap, CR 11.3

    Ford 460
    365 hp @ 4600 rpm
    500 lbs @ 2800
    valve lift .519 / .519
    duration 316 degrees, 80 degrees overlap, CR 10.5

    I'm now more convinced then ever that the unstreetability of the 426 Chrysler hemi is a myth promugulated by 426 envists and haters.

    I ran a 327 Chevy with a 306 cam and stock valves and had to change plugs every 500 miles or so.

    You say that a Buick 455 "GN" (sic) "smoked" a 426 hemi. Okay, you don't say where this was documented, and "smoked" is a pretty ambiguous term. I think I'd like to see the actual times to find out what "smoked" is really like. But in 1971 the 455 Buick "GS" Stage 1 engine was rated as follows:

    345 hp @ 5000 rpm
    400 lbs @ 3000 rpm
    valve lift .490 / .490
    Duration 326 degrees, 74 degrees overlap, CR 8.5

    Dusty
  • modvptnlmodvptnl Posts: 1,352
    But you're all over the place with it.

    The Ford motor comparo sort of makes my point. look at the torque numbers and the RPM attained.

    BTW that 429 was also the PI engine in my parents '71 LTD and was as docile as anything ever made but would turn the tire into molten rubber.

    Of Course the hemi had no detonation problems on the fuel available back then. But when smog laws and crap gas came on the scene the Hemi shortcomings were exposed.

    The shootout was staged by HOTROD(sorry, I thought I had posted that)and while I'm not a Buick fan, I thought there was a BUick that was touching close to 500 pounds of torque.

    The current trend of undersquare motors sort of explains in a way why the hemi wasn't a good street engine. To have any kind of compression and lift the piston is a very mis-shapen design. Forced induction, two plugs etc. can overcome this. But why, when there are more efficient STREET motors available.

    Look, it's been fun. BUT, it's getting counter productive. The hemi's main advantage is it's cross flow head and ability to use massive valves, both which promote incredible air flow. IF a hemi design is being utilized(the great air flow) it will actually hurt low end performance/torque.

    My only/original comment which I still stand by is that the hemi combustion chamber will not magically make more torque.....even with all else being equal.

    P.S. I love the 426 Hemi. But if its performance was soooo much better(in a street application) it easily would have been used in place of the 440 and production cost differences would be minor.
  • dustykdustyk Posts: 2,926
    >>The Ford motor comparo sort of makes my point. look at the torque numbers and the RPM attained.<<

    I fail to see the point here. The 426 made 490 lbs @ 4000 and the 429 CJ made 450 lbs @ 3400 despite the hemi displacing less ci. I think you're making the assumption the 426 had to be less at 3400 RPM. Not necessarily. Without knowing the torque curve the 426 could actually being producing more torque at the same RPM rating of the 429. Worse yet, it is more likely that the 429 made less torque at 5000 RPM.

    >>BTW that 429 was also the PI engine in my parents '71 LTD and was as docile as anything ever made but would turn the tire into molten rubber.<<

    That's probably true, but I don't believe your parent's LTD 429 was the same "state of tune," either. According to my 1971 Engine Data Book the LTD 429 was rated at 320 (2V) or 360 (4V) HP. Both got the 256 degree camshaft, smaller valves, etc. Now hat state of tune will increase torque.

    >>The current trend of undersquare motors sort of explains in a way why the hemi wasn't a good street engine. To have any kind of compression and lift the piston is a very mis-shapen design. Forced induction, two plugs etc. can overcome this. But why, when there are more efficient STREET motors available.<<

    The trend towards square is the result of lowering the power band in an effort to meet government fuel consumption and emissions requirements. That's all. Any engine that can produce 1 HP per cubic inch is not inefficient, lumpy piston or not. I might add that Chrysler built hemis from '51 through '58 that were not only as good a "street" engine as anybody elses, but did so with better then average performance for their displacement.

    >>Of Course the hemi had no detonation problems on the fuel available back then. But when smog laws and crap gas came on the scene the Hemi shortcomings were exposed.<<

    Ridiculous. The 426 was circa '66-'71. When octane was lowered by 1974 every '66-'71 high compression performance engine had the same problem. The 426 was no anomaly.

    >>P.S. I love the 426 Hemi. But if its performance was soooo much better(in a street application) it easily would have been used in place of the 440 and production cost differences would be minor.<<

    The fact is that the 426 hemi was sold because Chrysler had to make so many to qualify the engine for racing. And, the PR department at Chrysler wanted to further their performance image by offering these engines to the public. I suspect that a certain portion of these engines were either given the testosterone treatment for track use or the engines yanked for even more serious race contenders. Over the years, I can't think of another engine that I've seen in either condition more than the 426 hemi.

    I realize that my opinion is counter to the conventional wisdom. However, I, too, stick by my original statement. You say that you doubt that the new 5.7 is not a true hemi. I suspect that you've seen the advertised specs and cannot fathom this level of performance from a hemi "street" engine.

    Since the last production hemi was made in the early '70s, there have been huge advances in combustion efficiencies developed for internal combustion engines. These are not exclusive technology gains that can only be applied to engines with wedge combustion chambers. I guess you're on record that the new Chrysler 5.7 can't be a hemi. You may be surprised.

    Dusty
  • spokanespokane Posts: 514
    Withe the escalation of OHV V8's in the fifties and sixties, the long-stroke engines gave way to undersquare designs. The popular 289 Ford, for example, was rather extreme with a Bore/Stroke ratio of 1.39:1. In the subsequent era of emissions control, but still using carburetors, new designs were usually square to mildly undersquare. With today's engine control systems, is there any predominant design philosophy with respect to Bore/Stroke ratios?
  • modvptnlmodvptnl Posts: 1,352
    I think you have that backwards. Oversquare has been the trend until recently. The 289 has a bore of 4" with a stroke of under 3" the 302 is 4X3 and the the 351 4 X 3.5. All predominantly OVERSQUARE. Current trend seems to be undersquare, bore smaller than stroke.
  • modvptnlmodvptnl Posts: 1,352
    I would like to think if all things being equal that a hemispherical head somehow was more efficient(made more power even at lower RPM's) that it would be a much more popular design given the curent state of OHC and multivalve technology. A hemi certainly couldn't cost more than a current OHC/multivalve setup.

    I will reserve judgement on the 5.7 "hemi" when I see it. Like I've stated, there are current wedges (GM LS1's and Ford's 5.4) both making similar power/torque.

    I do remember our 429 PI having 365 HP. (It could have been 360) but it was in a very mild package being in a family cruiser and all.

    "Ridiculous. The 426 was circa '66-'71. When octane was lowered by 1974 every '66-'71 high compression performance engine had the same problem. The 426 was no anomaly."

    True, but '72 was the advent of tighter emissions and the hemi was a more difficult motor to make work. This was the demise of the big port Cleveland heads also, IMHO. This has been my contention all along. When things went south and compression had to be lowered the hemi was not as adaptable as a low compression smog motor.

    "
  • dustykdustyk Posts: 2,926
    >>True, but '72 was the advent of tighter emissions and the hemi was a more difficult motor to make work. This was the demise of the big port Cleveland heads also, IMHO. This has been my contention all along. When things went south and compression had to be lowered the hemi was not as adaptable as a low compression smog motor.<<

    Of course, early hemis were low compression by '60s standards (331=7.5CR, 270 & 291=7.2CR) and compression alone had nothing to do with meeting emissions as we all know now. But I believe your basic contention is that the hemi was not as adaptable to low emissions because it was a hemi. If so, that's completely false. What killed the 426 in 1972 was the economies of scale tipped heavily against it. Could a hemi of any displacement be made to meet emissions? Definitely yes. Was it worth doing to an engine that saw less than 2500 unit sales in 1972? Definitely not. Besides, by 1972 NASCAR had indicated that the 426 hemi would be soon legislated off the track, so Chrysler had no other reason to keep producing that engine.

    The 440 wedge was kept because it had much higher production numbers and was the ultimate prime mover for Chrysler's still popular police cars. Thus, the investment to meet emissions was quickly amortised.

    And what happened to some of those other "streetable, better emissions, better torque, non-hemi engines" of the period? Chevrolet kept the 454 because it had production numbers and GM's resources could better afford it, although I'm pretty sure it was dropped for a few years in the late '70s (could be wrong here). But the 400/402 didn't live much longer than the 426 hemi. Neither did the 500 Cadillac or the 460 or 429 Fords.

    Dusty
  • modvptnlmodvptnl Posts: 1,352
    My contention is that if the hemi was soooo superior and adaptable it would have been continued in one form or another. It was/is a difficult engine to control flame travel on if it is to have any performance. How can you debate this? The piston on a true hemi will have a mis-shapen dome with valve cut outs. It has flaws. It needs to rev to utilize it's better air flow. I don't know anything about the early hemis you keep bringing up. But again, if sooo much better, why did they die out?

    Of course the Hemi of the early 70's could be made to meet emissions. But at what cost??? Again, using your terminology of all things being equal, take a low compression smogged 440 and a low compression choked up 426 Hemi and the 440 would have the same if not better performance at lower, car/truck, applications. In other words no need for a hemi at these lower performance needs. Can you honestly tell me that if a hemi head provided better performance in these applications that Chrysler wouldn't have adapted the hemi to the 383/440 line up?

    Your 400/402 info is flawed because the 400(actually was the 402, unless it was the 400 small block) basically was/is the same motor as a 454, which is still basically the new 8.1.

    460's were still produced through '98 in light trucks. And I'm pretty sure the 372/429 (the same 385 series as the 460) is still used in medium trucks.
    Don't know Cad history, but didn't the whole division downsize???
  • spokanespokane Posts: 514
    Oops...sorry. My typo caused the question to be nonsensical. Yes, recent trends have been toward undersquare designs. In connection with the new combustion chamber, valve, and port geometries, do you see any future specific trend in the Bore/Stroke ratio parameter? I had understood that the undersquare trend was initially motivated by air quality (NOx reduction?) requirements and wonder if that is still true with the present engine management and catalytic exhaust treatment technology.
  • modvptnlmodvptnl Posts: 1,352
    I think you're exactly correct in your emissions statement. My opinion is that an oversquare design has a distinct advantage at higher rpms(less piston piston speed being the main one) but the drawbacks are controlling swirl/flame travel etc. with a bigger bore. While all out race motors(top fuel) may benefit from a hemi and an oversquare high revving layout. I predict as emission requirements get tighter you'll see more variable multi valve small bore motors.

    The new VW commericial actually touts its undersquare design as some great breakthrough!!!!
  • spokanespokane Posts: 514
    Your reasoning certainly seems right, Modyptnl. With respect to variable valve timing, if the electric solenoid-operated valve concept comes to fruition, don't you suppose a set of engine computer algorithms will allow an engine to be either powerful or economical on demand - but could re-open many of the engineering questions associated with swirl, flame propagation, combustion chamber shape, etc.?

    VW's marketing of "undersquare" is curious. As I recall it, Honda touted its 'Compound Vortex Controlled Combustion' (CVCC) technology prematurely in about 1980. When that engine actually reached the market, it was labeled "CVCC", but did not utilize the compound vortex fluid flow concept.
  • dustykdustyk Posts: 2,926
    ..... You have built strawman arguments using embellishing vernacular. I never said that a hemispherical combustion chamber is "soooo superior" or "sooo much better," nor did I say that there were no negative aspects to the design. In fact, I have yet to quantify the difference at all!

    >> Of course the Hemi of the early 70's could be made to meet emissions. But at what cost??? Again, using your terminology of all things being equal, take a low compression smogged 440 and a low compression choked up 426 Hemi and the 440 would have the same if not better performance at lower, car/truck, applications. In other words no need for a hemi at these lower performance needs. Can you honestly tell me that if a hemi head provided better performance in these applications that Chrysler wouldn't have adapted the hemi to the 383/440 line up? <<

    Despite your complete rejection, this bears repeating again. By 1972 with tighter federal emissions standards, CAFE, Chrysler's 426 being legislated out of NASCAR, the significant cost difference in building a hemispherical combustion chambered head, it just didn't make sense to build a (or the) hemi. Conversion of another block to a hemispherical combustion chamber would've added a bout 200 lbs to engines that were quickly being made in less numbers and going out of fashion. By 1974 sales of big block motors had fallen precipitously. The writing was on the wall for auto manufacturers in 1970. Engines would need to get smaller, lighter, and they would be put into increasingly lighter platforms in order to meet the future federal standards. For the degree of benefit, modifying a current design to make it a hemi just wouldn't have been logical. Put Chrysler's perennially tentative financial condition into the equation, and even more the reason. As part of the agreement with the US government for loan guarantees, Chrysler had to discontinue big block motors in 1980 anyway.

    >> The piston on a true hemi will have a mis-shapen dome with valve cut outs. It has flaws. It needs to rev to utilize it's better air flow. I don't know anything about the early hemis you keep bringing up. But again, if sooo much better, why did they die out?<<

    The '51 through '59 Chrysler hemis were phased out simply because they were too expensive to manufacture. Even the polyhead motors were more expensive and with the exception of the 318A, were gone by 1960. The lighter weight and cheaper wedge combustion chambers were easier to cast, more tooling and machine friendly and hence, produced higher investment recovery numbers.

    The piston shape of a "true hemi" would be a pure, symmetrical, unadulterated half sphere. So a "true hemi" has never been built. As far as adding valve reliefs the same law of physics would apply to any combustion chamber utilizing them. Air-flow across these depressions produce ebbs and back currents to various degrees in ANY design. There is no explanation as to why this would be different in a hemispherical combustion chamber, nor for that matter, why corrective design applications wouldn't apply. Your "it needs to rev to utilize it's better air flow" statement is self serving. It apparently assumes small valves, short valve lifts, and short durations are not compatible with or would not be used in a hemispherical combustion chamber. If so, that's patently incorrect. In fact, the hemi chamber has a propensity for broad torque and power curves, and I can see where valve component dynamics could be optimized for the hemi that could deliver performance not otherwise be as easily obtained in a wedge chamber.

    >> It was/is a difficult engine to control flame travel on if it is to have any performance. How can you debate this?<<

    Flame propagation maladies are present in just about any executed design. Wedges have them, too. In fact, I happen to have helped in solving a major flame propagation issue while at GM in the late '60s. GM's (actually, Chevrolet) inline 6 cylinder engines were probably the worse ever for this despite being wedge chambers. The problem was so acute that poor flame front control was responsible for so much manifold inversion that early versions had a pronounced tendency to pull the throttle plate closed during engine advance resulting in throttle flutter.

    Now I claim no specific authority on the hemispherical combustion chamber since my days at GM were dedicated to projects not related. However, your repeated contention about flame propagation doesn't make sense. The hemispherical combustion chamber has several advantages over a wedge design unrelated to flow. It is inherently high in volumetric efficiency. The chamber roof is open allowing for streamlined ports and less crowding around the valve edges reducing overall induction resistance. In the Chrysler-executed 426 version, the chamber shape formed at TDC has less chamber surface area in relation to volume contributing to less heat rejection and lower carbon build-up. It is a combustion environment requiring short flame travel, not long, and this characteristic contributes to increased combustion consistency and commensurately increased combustion efficiencies at lower flow rates.

    Dusty
  • modvptnlmodvptnl Posts: 1,352
    There have been many designs since the hemi. Including many more expensive OHC and 4 valve heads. Why wouldn't manufacturers embrace a design that is so wonderfully efficient? Especially with every last bit needed for CAFE? Why is the OHC from dodge a wedge? That surely has to be more expensive to build than an OHV.

    Your big block not being needed theory is silly in that there were still large sedans and trucks and motorhomes still using them in large numbers. The 440 did as good if not better job than a hemi in those applications.

    A hemi chamber,of course, is parabolic. The piston isn't what is hemispherical. There are a few current head designs(the Ford OHC's come to mind) that have swirl inducing bosses to enhance low speed mixing. So again, your streamlined open roof with unobstructed ports can actually be a detriment for low speed mixing.

    Why would the "new hemi" have 2 plugs?(if indeed it is a hemi) The bottom line, again, is a domed piston will have more flame travel problems than a flat or even dished piston.

    I'm curious to what your response is to your comment the big block chevies and Fords being phased out shortly after the hemi when they are still in production in one form or another.

    The bottom line is that if it was such a great, efficient VE design it would be more widely used. C'mon, how can it be more expensive to produce than a DOHC 4 valve or even an OHC 2 valve.
    maybe because it just doesn't work when more efficient, lower rpm power is needed.
  • dustykdustyk Posts: 2,926
    >> There have been many designs since the hemi. Including many more expensive OHC and 4 valve heads. Why wouldn't manufacturers embrace a design that is so wonderfully efficient? Especially with every last bit needed for CAFE? Why is the OHC from dodge a wedge? That surely has to be more expensive to build than an OHV.<<

    I believe the hemi chamber is more efficient. If the Dodge OHC engine you are referring to is the new 4.7 V8, information that I've read indicates it's a polysherical combustion chamber, not a wedge.

    >> A hemi chamber,of course, is parabolic. The piston isn't what is hemispherical. There are a few current head designs(the Ford OHC's come to mind) that have swirl inducing bosses to enhance low speed mixing.<<

    The chamber isn't a true hemisphere either. As far as swirl goes, are you saying that swirl cannot be induced in a hemispherical combustion chamber?

    >> So again, your streamlined open roof with unobstructed ports can actually be a detriment for low speed mixing. Why would the "new hemi" have 2 plugs?(if indeed it is a hemi) The bottom line, again, is a domed piston will have more flame travel problems than a flat or even dished piston. <<

    Combustion chamber design technology is not static. Two plugs per cylinder could be employed for other reasons, similar to the Nissan and others. If a domed piston is fitted to most wedge chamber designs, I would agree that flame propagation might be a problem. But apparently you are not familiar with the actual shape of the hemi chamber used in the new 5.7. Please example some documentation that supports your contention that all hemisherical designs must suffer in this area.

    >> I'm curious to what your response is to your comment the big block chevies and Fords being phased out shortly after the hemi when they are still in production in one form or another.<<

    First, Chrysler was out of the medium and large truck business by 1975, motor home chassis by 1977. No need for big block motors, especially in the pitiful production numbers Chrysler had then. Chrysler stopped producing big block motors for their cars and trucks in 1978. As for cars, Ford dropped the 429 in 1973, I the 427 and 428 were gone soon after. The 400 was dropped in Ford and Mercurys in 1978, Lincoln dropped both the 400 and 460 in 1979. Chevrolet dropped their big blocks cold in 1977, Buick, Pontiac and Olds dropped theirs (403) and Cadillac theirs (425) in 1979.

    As for trucks, Chevrolet/GMC dropped the 400, replaced with a lower compression, lower HP version of the 454 in 1979. Ford dropped the 360 in 1974 and the 400 in 1982. The 460 was introduced into the Ford HD truck line in 1978. Both of these examples are the result of the first federal emissions standards impacting trucks and the manufacturer's consolidation of power plants. It was easier in the late 1970s and early 1980s to overcome the ravages of emissions with larger displacement designs, and then only in trucks. I might add, these engines sometimes required significant investment in cylinder head redesign to meet emissions anyway. It didn't make sense to offer a broad range of power in incremental packages. Everybody reduced engine line-up. The fact that they or their offspring are produced today is totally irrelevant to the events of the 1970s. First, they have experienced significant changes in head, intake, and exhaust design to meet emissions and increase efficiency. Second, they are here today because gasoline is cheap and rear-wheel drive trucks are in vogue. But my point anyway was specifically Chrysler, which obviously had no need for big block motors of any type.

    >> The bottom line is that if it was such a great, efficient VE design it would be more widely used. C'mon, how can it be more expensive to produce than a DOHC 4 valve or even an OHC 2 valve.
    maybe because it just doesn't work when more efficient, lower rpm power is needed.<<

    More than two full decades elapsed between the last production 426 Chrysler hemi and the DOHC trend in American production engines. We've seen low numerical axle ratios, the Wankel, diesels, turbo charging, 2-4-6-8, water injection, come and go in American cars. Since the last 426 hemi great advances have been made in materials and production technology which puts an array of designs within easier and less expensive reach. The hemispherical combustion chamber design theory was never popular with Ford and GM, even though both would produce them. Chrysler was in almost constant turmoil, internally, and greatly distracted. To their credit they consolidated scarce research resources to improve the wedge combustion chamber design and for a number of years their "small block" motors met emissions without the costly add on devices (air pumps in particular) that robbed power and performance from their competitors engines. For the same reasons Chrysler quit making them, neither Ford nor GM wanted to invest in a chamber design they had little research experience with and would cost more to tool and produce than current designs.

    Dusty
  • modvptnlmodvptnl Posts: 1,352
    A lot of your big block info is waaaay off. To drop a 429 in favor of a 460 doesn't mean anything. Ford still used the 460 in LTD's until '78/79. The whole car line was down sized, not just the motors. The 402 AKA 400 and 454 is the same family. Ford 400??? Why are you bringing up a small block??

    "I might add, these engines sometimes required significant investment in cylinder head redesign to meet emissions anyway"



    BINGO!!!! If the hemi would have been more efficient for these applications it would have been incorporated!!!



    Please explain, the 426 was the ONLY true domestic hemi. The Ford was a crescent shaped dome(called the semi-hemi) in the Boss and GM never made one(not sure what you mean by GM tried). Ironic statement IMHO in that if swirl were induced by changing the shape of the chamber you don't have a hemi any longer.

    This last statement made is probably what I've been trying to say all along. The basic canted valve dome type chamber can be utilized with smaller valves or swirl inducing technology or maybe even multi valve technology. But once you start messing with the chamber you can call it a hemi or hemi magnum or whatever you'd like but it wouldn't be a true hemi in the 426 tradition......because it just wouldn't work, then or now.
  • dustykdustyk Posts: 2,926
    >>the 460 in LTD's until '78/79. The whole car line was down sized, not just
    the motors. The 402 AKA 400 and 454 is the same family. Ford 400??? Why are
    you bringing up a small block??<<

    My information regarding the phase out of various engines was obtained by Chilton's. They do not list a 460 in LTDs in 1979. Only Lincolns. The various engines mentioned were to demonstrate the decline of big displacement power plants by all manufacturers. If you remember, your claim is that the 426 hemi was dropped because the hemi couldn't be a daily driver and was hard to meet emissions. My response has been consistently that the 426 hemi didn't have a future because of cost, low production numbers, and at a time when large displacement motors became dishonorable. While Chrysler's position was more acute, it is plain and simple that large engines by all companies were quickly losing favor for the same reasons: disinterest in high performance engines, decreasing fuel consumption, reducing manufacturing costs, meeting emissions.

    >>("I might add, these engines sometimes required significant investment in
    cylinder head redesign to meet emissions anyway" ) BINGO!!!! If the hemi would have been more efficient for these applications it would have been incorporated!!!<<

    Silly response. Why invest in expensive methods to accomplish this when wedge designs would meet emissions with less cost? To make a 318 or 360 small block Chrysler into a hemispherical engine in 1972 would have been illogical. The added weight of the increased mass in cylinder heads alone would have been a negative (the 318 and 360 were already heavy enough), much less developing new tooling and manufacturing lines. It was cheaper to make the wedge chamber engine meet emissions, not because the hemi chamber wasn't capable, but because they were already wedges! Even if it would've been MORE difficult to meet emissions WITH A wedge, it would have been cheaper to stay with that design to reduce tooling and manufacturing costs. Proof that a hemispherical combustion chambered engine meets emissions and low-speed driveability requirements, there has been a hemi engine in production and used in both cars and trucks from 1974 to 2000. Maybe this company hadn't heard that it couldn't be done!

    >> Please explain, the 426 was the ONLY true domestic hemi. The Ford was a crescent shaped dome(called the semi-hemi) in the Boss and GM never made one(not sure what you mean by GM tried). Ironic statement IMHO in that if swirl were induced by changing the shape of the chamber you don't have a hemi any longer.<<

    In the early seventies Oldsmobile made several versions of "W" engines incorporating very radical valve and cam arrangements. One of the first engines was a hemispherical combustion chamber with a typical two valve per cylinder layout, then progressing to a four cam, four valve motor. Each variant got a number (W40, 41, 42, 43, etc.). The combustion chamber was purposely not referred to as a "hemi" even though the head chamber shape contained the same angular profile as Chrysler's 426. Ford produced "hemi" kits in the early fifties. These converted the Ford flathead, as I recall, to a hemispherical combustion chamber. If you cruise the web, you'll find these, I believe.

    >> This last statement made is probably what I've been trying to say all along. The basic canted valve dome type chamber can be utilized with smaller valves or swirl inducing technology or maybe even multi valve technology. But once you start messing with the chamber you can call it a hemi or hemi magnum or whatever you'd like but it wouldn't be a true hemi in the 426 tradition......because it just wouldn't work, then or now.<<

    Haven't a clue what you're trying to say here. In reference to the new Chrysler 4.7 motor, I cannot find any Chrysler literature source that calls it a "hemi." In fact, several independent sources use the phrase, "not a true hemi." But beyond that your claim is just that. Swirl is required in a wedge chamber because there is a large dead area on the other side of the valves furthest away from the spark plug bulkhead. That flame front cannot reach that area reliably and combustion efficiencies cannot be raised without flow restricting swirl techniques, especially in a conventional design where the valves are placed in the middle of the chamber roof, side-by-side.

    A hemispherical chamber that places the spark plug in the chamber epicenter has a more equal and much more symmetrical flame pattern. In addition the plug is cooled by the mixture stream. It is true that flame propagation will not reach the extreme lower edges in a STATIC CHAMBER. However, turbulence-producing piston profiles are able to scavenge these small areas the same as swirl inducing techniques used in wedges, except without the inherent induction losses.

    Now, you have continually referred to the 426 "hemi" as if it is the quintessential hemispherical combustion chambered engine. It may be quintessential, but it, too, is not a "true hemi." Everyone who knows anything about hemi motors knows that the 426 CID motor manufactured by Chrysler from 1966-71 contains a near trapezoidal chamber roof. The motors you appear to know nothing about are the "true" hemis built by Chrysler from 1951-59.
  • andre1969andre1969 Posts: 23,571
    Last year for it in passenger cars was 1978. It did not make it into any of the downsized "Panther" bodies. The 400 hung around for 1979, but only in the Lincoln Continental 4-door and Mark V coupe. They were just boat anchors by then, down to something like 166 hp.
  • modvptnlmodvptnl Posts: 1,352
    Your comment that the 429 was dropped in '73 was why I mentioned the '78/'79 460 LTD's.

    Look, we'll NEVER sway each other's opinion. It's just that if the hemi was so much more efficient at all engine operating parameters, it would have made a resurgence a long time ago. Efficiency to me in a production (not race motor) translates not only to the PEAK power produced but the all important emissions and CAFE while doing it.

    There has been so much spent to extract a good balance between performance, emissions and economy that if the hemi were to have an advantage it certainly would have been on new LS1's or the 4 valve Ford motors or the OHC chrysler and Ford motors. You can't tell me that a hemi with all its advantages would be more costly to build than any of these motors(with the exception of the LS1, even though it is a fresh, clean sheet design)

    As far as a flat head Ford with a hemi head....I can't even envision this simply because of the non-OHC layout.
  • When I was much younger I was part of a racing team that ran a twelve port Wayne Hrning head equipped GMC 302 c.i.d. in line six cylinder engined roadster. The thing was a torque monster (for it's day). The two competitors who gave us fits were 1) a Ardun valve in head conversion Ford (originally a flathead V-8) and a built up Dodge 341 c.i.d. hemi engine. Both were strong. Both were fast and both won consistently at the 1/4 mile drag races at L.A.D.S. Raceway and at Colton (both in So. Calif.) My money still rides on the hemis (when built right) to get the win consistently. Those 392's and 426's are awesome!
    Another engine that still impresses me is the Mopar 340 w/ six pak.
This discussion has been closed.