starting line gear ratio?
 

passing the hot AZ Summer afternoon reading...
in Dick Millers book, the starting line ratio chart is interesting, but...
[target ratio is 11.25]

with my 2.64 low 4 speed, I would need a 4.56 gear. I cant believe that a 350 hp/3550 lb car would ever leave hard enuf to go 12.20 [unless a 9,000 launch-and I aint gonna do that]. even a 2.20 low with a 5.13 [11.29] seems way to old school.
so is this just theory or is this chart for real?

where does finish line RPM come into the equation?
educate me.
thanks Rod in AZ

Re: starting line gear ratio?
 

Is that is like saying 12-1 AF ratio is perfect..
Test it.
Keep going up on SLR and find what your combo likes.
Rear gear selection and tire size for finish line RPM and MPH
BTW back in the old school days It seemed that the sticks we played with liked about 20% more SLR than the automatics. That may not be the case these days with modern converters and clutches...

Re: starting line gear ratio?
 

How about 21.39?

Jim Caughlin
SS/ES 6019

Re: starting line gear ratio?
 

Tire height, flywheel weight, clutch, torque curve, and so many other things would factor into this.

Re: starting line gear ratio?
 

I'm sure my car was all wrong, but I used what I had available at the time- 25.5" slicks, 6.17 rear end gear, and 3.64 first gear.

As far as your horsepower, weight, and potential ET, your numbers sound about right. My car was about 250 horsepower, about 2,300 pounds, and launching at 9,000 rpm resulted in high 11s at about 110 mph. With a modern clutch, a lighter flywheel, and a closer-ratio transmission with a taller first gear, I'm sure it would have gone faster.

Re: starting line gear ratio?
 

watched vid on 289 mustang, ss/L 20.398 start ratio

Re: starting line gear ratio?
 

What is the intended combination, and combination? With my old M/S 85 5.0 Mustang, I ran a 3.19 low gear in the Jerico, and with 4.88 gears, that made for a 15.56 SLR, and with 5.13, a 16.36 SLR. That was with 29-29 1/2" tall tires. I would have liked to have tried a bit lower rear axle ratio, but for the Ford 8.8, there was nothing between 5.13 and 5.7. Unless it is a really lightweight car with lots of power, and borderline ability to hook up, I can`t imagine a 11.25 SLR would be anywhere close to ideal. My SB Ford 4 speed G Force bracket car also has a 16.36 SLR,albeit with 31" tall tires, plus an additional 25 MPH, but looking to add a bit more rear gear ratio, or shorter tires to give another 1 or 2 hundred RPM at the 1/4 mile finish line. Same with my old hot rod type cruiser, currently has a 2.78 low Toploader with 3.50 rear and 28" tall tires, a 9.73 SLR, and I am barely hitting 4th gear at the finish line. Plus at over 4000 pounds, the organic street style clutch isn`t very happy. Hopefully the 4.33 gears (12.03 SLR) will help performance, and clutch life, at the track. And if I was to decide to switch to a modern overdrive 5 speed, I would be looking for a low gear in the 2.8 to 3.1 range.

Re: starting line gear ratio?
 

This is what my software suggests.


Stan

Re: starting line gear ratio?
 

Back when I ran a stick in my car the SLR was about 19 to 1. With the same engine combo and a glide the SLR is 12 to 1. The engine is much better now and the car is about a second faster than it was with the stick.

Re: starting line gear ratio?
 

For what it’s worth, my brother ran a 58 Chevy wagon back in the 80’s in IHRA Super Stock (basically a econo modified engine). It was a 283 that weighed 3839 and ran a turbo 350 with a 6:83 Dana and 29 and 30 inch tires for the 1/8 and 1/4. The torque converter was pretty a good piece back then but could likely have been ran on the street now. The car held the IHRA class record before he bought it and did until he sold it. I don’t remember any 60’ numbers but the car got quicker after putting In a 2:75 low gear. Don Jackson