Door Car 1/8 mile Gearing ?

How many that race door car have them geared strictly for 1/8 mile racing?

If racing 1/8 mile, what gear ratios, tire dia, cu in, et ?

What is the known or estimated ET/MPH for the car?

mark, most bracket racer's don't have their car geared for optimum ET whether it be in the 1/4 mile or the 1/8th mile but f they were too it's safe to say that if they were to gear for 1/8th mile, a small block door car would have a mid to high 5 series gear and a big block car a high 4 series to low 5 series gear with the trans and tire they run influencing the selection of the correct gear ratio.

FYI, my Firebird has a 4.86 rear gear.

quote:

Originally posted by FootbrakeJim:
What is the known or estimated ET/MPH for the car?

5.9x - 6.4x sbc

Tire diameter has a lot to do with gear choice...figure out what diameter you are going to use first

quote:

Originally posted by "The Bender":
Tire diameter has a lot to do with gear choice...figure out what diameter you are going to use first

32"

quote:

Originally posted by 1320racer:
mark, most bracket racer's don't have their car geared for optimum ET whether it be in the 1/4 mile or the 1/8th mile but f they were too it's safe to say that if they were to gear for 1/8th mile, a small block door car would have a mid to high 5 series gear and a big block car a high 4 series to low 5 series gear with the trans and tire they run influencing the selection of the correct gear ratio.

FYI, my Firebird has a 4.86 rear gear.

So when gearing for ET, higher ratio better, and when gearing for MPH lower ratio better?

quote:

Originally posted by markemark:

quote:

Originally posted by 1320racer:
mark, most bracket racer's don't have their car geared for optimum ET whether it be in the 1/4 mile or the 1/8th mile but f they were too it's safe to say that if they were to gear for 1/8th mile, a small block door car would have a mid to high 5 series gear and a big block car a high 4 series to low 5 series gear with the trans and tire they run influencing the selection of the correct gear ratio.

FYI, my Firebird has a 4.86 rear gear.

So when gearing for ET, higher ratio better, and when gearing for MPH lower ratio better?

That's a trick question terminology speaking. A low gear ratio is a high numerical gear ratio and vice versa.

To remember that think of it low - slow on highway and high - high speed on highway.

You're crossing at 6700 now with a 4.56 converter slipping 21%. If you put a 5.29 in it, you'll cross 7200 converter slipping around 15%.

If your engine makes more power 7200 than 6700, you'll pickup a little mph. With a 5.29, it'll definitely improve the front half (incrementals) of the run.

I’m trying to determine the point in my car where more gain in mph comes with the least amount of et. I could possibly already be there.

Crossing the 1/8 finish line at 6550 -6600 now with an engine making hp to 7200 gives plenty of room to adjust gearing.

The reason I ask to hear from others geared 1/8 is to see what they use and the et /mph performance.

quote:

Originally posted by markemark:
I’m trying to determine the point in my car where more gain in mph comes with the least amount of et. I could possibly already be there.

Crossing the 1/8 finish line at 6550 -6600 now with an engine making hp to 7200 gives plenty of room to adjust gearing.

The reason I ask to hear from others geared 1/8 is to see what they use and the et /mph performance.

Having a 1.40 low you're kinda out there on an island of your own, most with a 32 tire plus run a 1.80 x 4.88 = 878 starting line ratio.

I haven't done the math but hypothetically speaking, if you went 5.29 I think that would have just approaching a 7.50 starting line ratio. Which is excellent actually, as far as easy on the tire.

1. optimum gearing will result with optimum ETs not MPH.

2. all your ET is made in the first 330 feet and 60 foot is everything to quicker ETs n/a

3. in the 1/4 mile you gear for optimum ET at 1100 feet not at the stripe.

1.40 low? Where did that come from?

You can ride the torque deadly consistent n/a methanol.

You can run methanol hard too, it'll be consistent.

Markemark has a unique situation, he has the best of both worlds, in low gear his will be easy on the tire while in high, if he goes lower gear he can ring the engine out a little rpm wise 7200.

This message has been edited. Last edited by: Mike Rietow,

quote:

Originally posted by "The Bender":
1.40 low? Where did that come from?

2nd gear in a th400

quote:

Originally posted by markemark:

quote:

Originally posted by "The Bender":
1.40 low? Where did that come from?

2nd gear in a th400

So you are leaving in 2nd?

FWIW I thought a 400 was 2.48, 1.48, 1.00

quote:

Originally posted by "The Bender":So you are leaving in 2nd?
FWIW I thought a 400 was 2.48, 1.48, 1.00

Yes and mine is 2.10 , 1.40 , 1.00

quote:

Originally posted by markemark:

quote:

Originally posted by "The Bender":So you are leaving in 2nd?
FWIW I thought a 400 was 2.48, 1.48, 1.00

Yes and mine is 2.10 , 1.40 , 1.00

OK, I guess you're trying to kill ET by leaving in 2nd then?

quote:

Originally posted by markemark:

quote:

Originally posted by "The Bender":So you are leaving in 2nd?
FWIW I thought a 400 was 2.48, 1.48, 1.00

Yes and mine is 2.10 , 1.40 , 1.00

Mark what was your reason for going away from the stock turbo400 gear ratios?

FYI, I've been running a turbo400 for 30 years in my race cars with the stock gearset.

Initially the 2.10 was to soften the launch, keep it on the convertor longer and was much better if starting lines were questionable. It did this well.

Then I started short shifting 1st keeping it on the convertor into 2nd. This gave me more of what I wanted, less et more mph and consistent RT.

After I tried FB the car several times using 2nd, I saw the same mph but less et. Then I installed the 1+2 TB and started leaving in 2nd. I definitely like this look on the track and am running 5-6 mph more than many with the same et. I can even be over a fender behind some cars dialed 0.25 faster than me at 100’ and run them down with more mph.

I’m at the point where I have a SLR that effectively reduces the front half of the run but allows more mph on the back of the run with 1 shift.

So my question is how much more mph could I gain by putting more gear (higher ratio) to run the back half without speeding up the front half by much. Is this proportional at some point?

This is my goal if making a gear change. This weekend in 2700’ of corrected altitude the car ran 6.34 @ 112.25. I’d like to go 6.29 /6.24 @ 113.75 or more mph given this weather condition.

I have 4.40 diff with 1.40 trans = 6.16 SLR. At what rear gear do I run out of mph gains and just keep reducing et or run out of that with a gear change?

Well, I'd say you'd have to try it to find out. But someone out there has probably been there before, hopefully you can find them......