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0 - 60 mph :)

7K views 28 replies 5 participants last post by  geeteeohguy 
#1 ·
Well I just used dragy and did my first 0-60 run. Needless to say, the launch was less than ideal, but the car is clearly underpowered. I will post the data shortly, but 0-60 mph was 7.6 seconds. I was hoping for 5.x....I have a bit of work to do.....
 
#2 ·
I love your post! So total newb question, when I floor my goat, and after I finally get traction, it seems like it downshifts, but I watch the RPM go over 4,000 and I'm worried it will not shift into the next gear, likely resulting in an explosion of what was once my beautiful engine, so I let off on the gas. Is there a trick here, should i be letting up on the gas to let it shift? Ok, maybe I made 4,500 once.
 
#3 ·
Well my car is a 4 speed manual and I am shifting at ~5000 - 5500 rpm. Your automatic should go above 4500 before shifting if you are going WOT.
 
#5 · (Edited)
The governor of your auto trans can be modified to shift higher or lower. My trans guy rigged his last bracket car to shift about 5200, if I remember correctly. He just launched in drive, & let the trans shift itself.

https://www.hotrod.com/articles/hppp-1203-recalibrating-turbo-400/

https://www.jegs.com/i/JEGS/555/62070/10002/-1

A healthy 400 should be plenty safe to 5500. But, most smaller cams don't make good power to 5500.

Anyhow, if you're afraid you'll over-rev & blow your engine up, you can install a rev limiter, & set it at 4800, 5000, or where ever you want it. I used a rev limiter on all my 455 bracket cars. They saved ALL of those 455's, some several times, when they'd break the trans or rear end.

https://www.ebay.com/itm/MSD-MSD-87...=18330126114198e0badaf31c47e8a132862842fdc94d

https://www.amazon.com/PerTronix-600-Digital-REV-Limiter/dp/B000CC9DAY#customerReviews

You can buy from Advance Auto & use an online 25% off code. That makes it the cheapest price for lots of parts. I've saved quite a few bucks with the 25% off deal.

https://shop.advanceautoparts.com/p...AUOrSn4kbf3QBo_aTQ0aAvZUEALw_wcB&gclsrc=aw.ds

Pertronix also makes a points replacement & HEI module with built in rev limiter.

https://www.summitracing.com/parts/pnx-d72000/
 
#6 ·
BigD - What about gearing ? My 4 speed + 3.55 + tire combo requires that I shift into 3rd gear to hit 60+ mph. Given all the low end grunt, would it not be better to have a taller rear and only have to do a 1-2 shift to hit 60mph and be easier to launch? (Plus added benefit of lower RPM on the freeway.)
 
#7 ·
As I see it, higher numerical gear ratios have only one main advantage. Straight line acceleration.

Here: are some of the advantages of lower numerical gear ratios:

(1) Lower highway & cruz rpm.

(2) Better gas mileage.

(3) Should give engine a longer life.

Some disadvantages:

(1) Less acceleration.

(2) Might cause more clutch wear, because of more slippage required for getting the car moving.

SO, for street driven cars, the best gear ratio is a compromise. And, it depends on the driving habits & goals of the driver.

(1) If you do LOTS of high speed freeway driving, then ratios between 2.41 & 3.08 might suit you best.

(2) If you prefer lots of acceleration, & don't really care about fuel mileage, then ratios between 3.55 & 3.90 might be better for you.

(3) So, the compromise gears might be 3.23 to 3.42. I think these were the only 2 options for the '78 W72 4-speed Firebirds.

All this is assuming a 1:1 high gear ratio. An overdrive trans changes things.

Taller or shorter rear tires can also change things, slightly.

4-speed manual trans are available with numerically higher 1st gear ratios, which will work better with numerically lower rear gears. My '69 GTO had a 2.20 1st gear ratio, with 3.90 rear gears. I loved it. But gas was lots cheaper back then. I think the most common 4-speed 1st gear ratios were in the 2.50's & 2.60's. I think 2.88, 2.98 & maybe even 3.08 are available.

https://midwestmuncie.com/product/a...her-4-speed-perfect-2-73-3-31-rear-end-gears/
 
#8 ·
Interesting.....I would have thought the car (with all the low end torque) would benefit from a 3.08 or even lower (taller) as the tires would not just spin and would save you a gear shift (time) from 2-3 in order to get to 60 mph.
 
#9 · (Edited)
If you have lots of tire spin, your 0-60 time is not gonna be quick, regardless of what rear gear you have. Back when I raced my '69 GTO with hard street legal tires, I popped the clutch at about 3000 rpm, but i couldn't go to full WOT until just before the tires quit spinning. If I went to WOT any sooner, the tires would just keep spinning for quite a while longer, resulting in a much slower ET.

With a numerically low rear gear, if the tires don't spin much, but rather hook up at low rpm, it might actually "bog" the engine down, til the rpm get up into near the peak torque range. The bog will be worse, if the cam does not provide much low rpm torque. So, the trick is to get just the right amount of tire spin, but not too much, & going to full WOT at exactly the right time.

With the engine in it's peak torque range, and the tires hooked up, acceleration will obviously be better with a numerically higher rear ratio. And, as for the extra shift, with a little practice, the shift only takes a small fraction of second. So, the numerically higher rear gear ratio will more than make up for anything lost to the extra shift
 
#10 ·
Average times 0-60 in the muscle car era for the GTO ranged from 4.9-7.5 seconds or so, depending on all of the variables covered by Big D. A 4 speed, 3.90 geared tripower '65 was seconds faster than a 2 speed automatic, air conditioned, 3.08 geared 4 barrel GTO of the same year. My '65 came with tripower, 4 speed, gauges, and a 3.55 posi. No power steering, no power brakes, no seat belts, no outside rearview mirror. I didn't mind the 3.55 gears when I got the car almost 40 years ago when the national speed limit was 55 mph. Where I lived, everybody cruised 60.....65 was a guaranteed ticket. When the law got repealed in the '90's, I changed to 3.36 gears and 29" tall rear tires, which allows a comfortable 70 mph cruise just under 3000 rpm. My '67 automatic car had a 3.36 open rear end.....I changed that to a 2.56 posi about 10-12 years ago. 80 MPH cruise is 2450 rpm getting 20-21 mpg.....90 mph is right at 3000 rpm. The engine runs cool as well. I use this car for long trips over open country. 1000 mile weekends are not uncommon. With my lazy gears, I'll bet my 0-60 is about 8 seconds.....but I don't care. My car will hold second gear until 105 mph....which is more than the top speed of many shorter geared cars.
 
#12 · (Edited)
#13 ·
Read it an weep. Keep in mind that the 376HP/421 HO got the Bobcat treatment. The car turned a 13.8 @ 106 MPH in the 1/4 mile - and that was with factory pipes with resonators removed and street tires - not slicks. On the 4-lap run of the road course, it covered the course in 2:01.33 to the Ferrari's 2:00.85 which was less than 1/2 second slower. The Ferrari took the advantage in the curves, but the 2+2 ate it up in the straightaways hitting a best speed of 127 MPH. The driver, Walt Hansgen, drove the 2+2 in 4th gear the entire track except one down shift to 3rd in the 55MPH hairpin. It was felt that if he had used 3rd more, his times would have been faster (ie beat the Ferrari).

My favorite part of the article, "When the throttle is suddenly pressed home and all six throats snap open, the effect is a stunning transformation. The noise level rises from a near-silence to a hard, flat roar. The pressure on the nape of the neck and the pit of the stomach is almost unbearable. The acceleration is phenomenal - the car is literally launched from a stand-still to a hundred-miles-per-hour faster than you can absorb the sensations - so fast that you don't even look at the instruments, just listen for the peaking point and slam the lever into each gear as hard and as fast as you can."

In each book, one written by DeLorean and the other Schornack, they both mirrored the test and the results.

It's all about torque and bite at the rear wheels. No doubt the longer wheelbase and additional weight of the 2+2 was a contributing factor. And how much HP/TQ did that Royal prepped engine really have? Bottom line, we will never know for sure, anymore than we can say the 0-60 times for the Shelby cars are correct or can ever be reproduced. :thumbsup:
 
#14 · (Edited)
Believe it if you choose to.

IMO, a 13.8 @ 106 mph 1/4 mile car will not run anywhere near a 3.9 sec 0-60. The math just don't add up. The Royal Bobcat treatment couldn't work that kind of magic.

Hey, the Cobra wouldn't do it even with a 427 @ around 2500 lbs.

https://www.ultimatespecs.com/car-specs/Shelby/15193/Shelby-Cobra-427.html

https://www.topspeed.com/cars/shelby/1966-shelby-cobra-427-super-snake-ar25745.html

https://www.hemmings.com/blog/article/american-icon-1967-shelby-427-cobra/

https://www.supercars.net/blog/1965-shelby-cobra-427-roadster-history-specifications-performance/
 
#15 ·
Agreed BigD, there is no way one could launch a stock 4400 # car on tiny rear wheels of the day and get 3.9 seconds 0-60. There was definitely a lot more going on with that Royal Bobcat. To put that in perspective, my 600 hp + (modified and whp), all wheel drive AMG takes 3.2 seconds to get to 60 seconds and that has been a lot of work. The same car is turning the 1/4 mile in low 11's at 127mph.

Just shifting the gear, 1-2 and 2-3 will add ~0.5 seconds for a very quick shifter (world class), whereas most normal people would be closer to 0.5 seconds for just the 1-2 shift or 1 second for 1-2 and 2-3.
 
#16 ·
Big D, I have the old magazine road test somewhere on the '65 2+2....it is a rather famous road test, probably on line these days. The 421 Bobcatted 2+2 did in fact clock a 3.9 0-60 time back in the day. I have no idea what ELSE was done to the car or the clocks.....but the test stands, believe it or not. Remember, Jim Wangers had those 2 ringer '64 GTO's for the Road and Track road test in Sept of '63.....those cars had built 421 engines, passed off as 389's. The actual HP of the Super Duty 421 engines in the early '60's was over 500.
 
#17 · (Edited)
"...but the test stands, believe it or not..."

I believe the test was reported. But I absolutely don't believe that they actually managed to get a car that heavy to run 0-60 in under 4 seconds, especially with only 3.42 gears. It just defies all the laws of gravity, math, & mechanics.

In fact, since the light 427 Cobra couldn't do it, I'd like to see exactly what it would take to make a 3500 lb car that quick, much less a 4400 lb car.

Hey, you guys can believe it if you want to. But that don't mean the car was actually that quick.

This blown 707hp/650 torque 8-speed Hellcat only managed a 3.4 sec 0-60 time. Running 0-60 in under 4 sec just ain't that easy to do, in a heavy street car. Takes LOTS of power, gearing, & traction.

https://www.caranddriver.com/review...challenger-srt-hellcat-automatic-test-review/

But hey, whatever ! That's all I'm gonna say about it.
 
#22 ·
Well I am learning how to launch the car a little better, but nowhere near where it could / should be. When bring the car up to ~2 - 3K RPM, I just get too much wheel spin. So far my best 0-60 mph is 7.34 seconds using Dragy. Honestly I think I could get ~1 second better if I could launch the car properly.
 

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#23 ·
You don't want to dump the clutch at the higher RPM's as you found out. Tires go up in smoke or you might experience some wheel hop.

You will have to develop a technique to launch the car. What I have done in the past is to find the RPM you can let the clutch out quickly and get the tires to spin about 1 revolution breaking traction. Then the tire will catch and it'll seem like the engine is going to stall, the front end may nose down a little, and then quickly nail the gas all in one smooth motion.

What is happening, at least what I think in happening, is the torque of the engine will shock/break the tires loose just enough to lose traction, but not fast enough to keep spinning. And, you are lifting up the nose preloading the suspension to put some weight on the tires. As the tire grabs pavement because it is not spinning too fast, the engine almost goes into a quick stall and the nose then drops down. At that instant, you hit the gas throwing the weight of the car back on the rear tires which have grabbed pavement due to the slow roll forward you have put into the car, and it takes off.

I used to rev the built 409CI I had with the 4-speed to 2,000 RPM's with the wide M-50's and 3.08 posi. I would let out the clutch, hear the tire rotate/chirp, give it a split second to recover, and then hit the gas and take off like a wild banshee. Higher RPM's only produced earth shattering wheel hop and I would go nowhere waiting for the rear-end to stop bouncing and then take off. Good way to lose a race - and I did, but almost caught the guy at the end of the track with all the power that engine had. Lesson learned, I never launched the car at higher RPM's.

You can also try lowering air pressures in the rear tires which may or may not give you a little more bite. Just going to have to experiment a little. :thumbsup:
 
#24 ·
Jim, thanks for the suggestions. With the amount of torque these cars produce, I really think a taller rear end gear (like 3.08 vs my 3.55) would benefit 0-60 runs, launches, mpg, etc. I have no idea how guys launched these cars back in the 60s with the skinny stock tires and a 3.55 rear.
 
#26 ·
I have a 1967 article where a '66 GTO is Bobcatted and taken to the strip. The car had a 389, tripower, 3.90 posi, M-21 4 speed, and was fitted with 9" wide slicks. Other mods were 90/10 front shocks, removal of the front sway bar, backed off control arm bushing bolts, and Lakewood solid U-joints. Their technique? They revved it to 5200 RPM and dumped the clutch. They had a best time of 12.43 in the quarter. When I was racing my 4 speed cars, I did it like Jim did, but never waited for a bog or hesitation. I simply let out the clutch at the same time I floored it.....the technique was to feather the clutch enough to keep wheel spin down to a minimum. As soon as the clutch and tires hooked up, I was gone. Tire's were wide bias ply 50 or 60 series, run at lower pressures, and I ran 3.55 gears with Lakewood traction bars, which I painted flat black for stealth.These helped immensely, eliminating wheel hop and helping the front end to come up and plant the rear tires. It's all in the feel and technique. I know a guy on the Corvette forum who runs 12 flats with a 4 speed, 327 inch '66 Corvette with a 4.11 rear gear and stock bias ply tires. He's even had magazine coverage.....the guy's name is Donny Brass. He has the launch and the powershift absolutely nailed.
 
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