nova2206

I have a 3550 lb 67 Chevelle with a 477 iron headed big block with a 400th tranny. It currently has a 1/4 mile set up with a 4.10 gear, tire are 12.50s, it runs damn good in the 1/8th at 6.26 or 6.27 in the heat with a 1.38 60 ft.. I never race a 1/4 mile so what is the right 1/8th mile gear.. I go into high gear about 2 car lengths from finish line.

us7race

It depends on how hard you want to turn it but I think more gear will definately help. How tall are the tires? At least a 4.56 if not a 4.88.

zipper06

us7race is dead on, if you are turning about 6200 in the 1/8 mi. lites, useing this calculator, and you want to turn 7,000 rpm. It comes out to 4.63 gears. BUT, there could be a hooking problem with the b/blk. We run 5.29 gears with a s/blk and run 5.90@118 and 10.5W tires but it doesn't have the torque of a b/blk.Here is the caculator that will help you decide.

http://www.wallaceracing.com/gearcalc.php

Zip.

sds10racer

hey zip, does that calculator take into account diff. shift points?

Tod74

That's moving for a car that heavy with only a 4.10 gear.

zipper06

No it doesn't, but if you go the site and click on index it shows a lot of different calculations.
I was assuming he's running about 6200 RPM in the 1/8 mi, since he said 2 car lgs. before the finish line he shifts to 3rd gear and 6.26/6.27 ET equals about 108 MPH.

JMO

Zip.

dparker

It may not help much to go to a lower gear, for the simple reason that right now your total gear ratio in low is 11.28 to 1. Your total gear ratio in low gear, if you were running a powerglide and a 4.88 in your rearend, would be a 8.59 to 1. If you went to a 4.56 rearend gear your total ratio in first gear would be only be 12.52 to 1. This is one advantage to running a turbo 400 over a powerglide, especially in a heavy car.
Going lower on your rearend gear will pick you up a little but you'll have to decide if it justifies the means, or expense. Just the few things to think about before you spend the moneys to upgrade your rearend.

nova2206

Thanks for all the great ideas, my reason for asking is because a good friend of mine had a set of 5.13 for a Dana laying around and I wanted to try them, went ahead and put them in today and I'm gonna try them this Sat, I'll get back on and let you know what happens. I have another buddy with a 3400lb car that runs close to the same set up with a 5.38 gear and he runs 6.0's so we'll see.
Again thanks for the help