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Or is that manual transmission GTX geared for 250 MPH in 3rd gear and 350 MPH at redline in 4th gear?
Now on the flip side of that, I think you could special order a tall ratio axle of around 2.06:1. When you figure that's about half of a 4.11:1, that means you'd hit peak hp at a theoretical 194 mph, and top out at 222 mph! Of course, it doesn't take into account wind resistance, which is going to be fierce once you get up over 100 mph or so. And IIRC, for every doubling of speed, wind resistance is actually squared?
I'd say that with a moderate gear ratio, and in tip-top shape, that '72 GTX might, *might* top out at around 145-150 mph. IIRC, some of the fiercest police cars of all time were 1969 Polaras running 440's and 3.23:1 axles, and that's about what they'd top out at.
As for turning 3500 rpm@135 mph in 3rd gear? Well, doing the math, I'd take a wild guess and say that would be a 2.45:1 axle? And again, that's not taking into account aerodynamic drag. And I seriously doubt that anybody would put a 2.45:1 axle in a '72 GTX. And you sure as hell don't want to rev something like that up to 6500 rpm! There are many modern DOHC engines that redline around there...some big monster of a 440 that's better at pulling out stumps and flattening mountains isn't going to want to rev that fast without scattering parts for a wide, wide radius!
Maybe that '72 GTX came out of Canada, and had a metric speedo! I know a guy in one of my Mopar clubs with a '66 Fury that came from Canada, and it set up that way.
1971 440-6pk Road Runner, 4.10 rear
104 mph@5400 rpm
1971 383-4v Road Runner, 3.55 rear
98 mph@5000 rpm
1971 440-4v GTX, 3.23 rear
110 mph@4700 rpm
Interestingly enough, this '71 GTX did list a top speed of 130 mph @5500 rpm (redline).
Another article from Motor Trend compared three different 'Cudas, a 340 auto, 440-6 4-speed, and a Hemi auto. The 340 was the author's favorite, as the 440-6 was just too much of a chore to drive, its carb setup impossible to modulate between moderate acceleration and flat-out. The Hemi was easy to drive, also, just keep your foot out of it on takeoff. Top end on the cars (all at redline): 340 (4.10 rear)- 101 mph, 440-6 (3.54 rear)- 109 mph, 426 Hemi (3.55 rear)-112 mph.
Surmise what you will, but I drove some of these vehicles on a daily basis, and trust me, by 100 mph, they were mostly used up and acceleration was pretty slow thereafter. Here's a shocker- Car and Driver tested a Saturn Aura XR that was quicker and faster in the quarter than the '71 GTX! As far as I'm concerned, the golden age of cars is now.
I'm kinda surprised though, that the car with the 3.23:1 ratio only made it to 110. I figured a ratio like that would be a good enough "middle of the road" ratio to give good top speed without hurting acceleration too much.
Sad thing is, though, that I had an '89 Gran Fury ex police car, with a 318-4bbl and a 2.94 ratio. It would top out at about 120 mph, according to the Michigan State Police, at least. Heck, even my old '69 Dart GT, with a 225-1bbl and 2.76:1 axle could break 100 mph pretty easily. I was afraid to take it much higher than that, though. It actually felt like it had plenty of power left at that speed, but I have a feeling it wouldn't have gone much faster.
LOL, I do a similar trick with my '85 Silverado in the warmer spring/summer months. I have an old '68 Dodge Dart V-8 air cleaner top that I put on the Chevy. It has the tall 5" or so air filter, and the top part is actually too big to flip. But the Dart's air cleaner, which is flat, sits nicely on top of the air filter and exposes a great deal of it.
I don't know how much it REALLY helps acceleration on that dog, but it does seem to take off a bit quicker when trying to merge onto a highway, for instance. And it seems to improve fuel economy a bit, maybe .5-1.0 mpg. Which, when you're dealing with maybe 12-15 mpg to begin with, every little bit helps!
It does make it a bit crankier in cooler weather though, and I have a feeling that it screws with emissions.
The car is still awaiting Shelby certification and is currently on tour with CARSTAR making $$$ for the Make-A-Wish Foundation.
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In the early '70s, Motor Trend listed under the specs that the speed in gears are limited by the length of the track and do not represent top speed.
This would also apply to the 340 'Cuda with 4.10 gears... 101 mph @ 5500 rpm, but the 340 could rev to 6000 rpm.
And the 109 mph @ 5000 rpm for the 440-6 bbl 'Cuda meant that it should be able to reach 120 mph @ 5500 rpm.
Back in the late 60's, they were able to get 440-powered Monaco and Polara copcars up to around 147 mph, with 3.23:1 gearing. Acceleration would suffer compared to those quicker ratios, but they were still no slouch off the line. Oh, and of course, the improved aerodynamics of today's cars helps out alot, too. Aerodynamics don't mean much from 0-60, but do come into play more in the quarter mile, and especially top speed.
What about them Challengers?
For 1974, you could still get a Charger with a 280 hp 440. By that time though, I think it was a hot 4-bbl, rather than a 6-pack or dual quad.
As for the Challenger and Barracuda, they wussed out very quickly. In 1971 you could get a 440 6-pack or the Hemi. But for 1972, the top engine was a 245 hp 340 smallblock. It was actually a good performer, and would embarrass many big-blocks, but it wasn't not Hemi! For '73 they started phasing in a 360 which had about the same peak hp, but it had a narrower power band than the 340, so it didn't perform as well.
By 1974 though, I think everybody was out of the high-performance game. Olds, Buick, and Pontiac used to offer high-output versions of their 455's, but I think they were down to around 250 hp by 1974, and by 1975 you'd be lucky to see 200-210 hp out of a big-block. The Chevy 454 put out 270 hp back in 1972, but by '74 I think it got cut severely, and even worse by '75-76.
Chrysler did still have a 255 hp 440 in 1978, which was about as powerful as it got by that time. The only catch is, they were only offered in the midsize Monaco/Coronet police cars! They were pretty quick, too...fast enough that they'd even give most modern police cars a run for their money.
I don't think high insurance rates played much of a part until the 1970's. If anything, most car companies were over-stating their hp in the 60's, rather than under-stating it. Horsepower is what sold cars in those days. Chrysler's 340 was one of the few under-rated engines...probably because if they listed its true horsepower, then people would question whether they really needed some of the bigger engines. It was rated around 270-275 hp with the 4-bbl. When the rating system went to net hp, it still had 245 hp, or about 89-90% of its gross rating. Many engines were lucky if their net rating was 70% of its gross rating, although to be fair, some engines had their compression cut at the same time, so there was a real loss in addition to the "paper" loss.