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Hemi's: any make, any size....What do you think?
smokin_olds442
Member Posts: 41
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.
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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 :-(
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.
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.
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?
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.
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
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!
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!!!
Kind of like assuming that smooth surfaces result in higher efficiency necessarily.
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.
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.
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.
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
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.
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.
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
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
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.
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.
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.
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."
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.
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.
Any ideas on, theoretically, which one would win a stoplight race?
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
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.
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
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.
"
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
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???
The new VW commericial actually touts its undersquare design as some great breakthrough!!!!
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.
>> 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
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.
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
"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.
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.
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.
Another engine that still impresses me is the Mopar 340 w/ six pak.