gearing

Hopefully this is the correct location for this question, I'm finishing up changing my car, it's a 466 with TFS 290 heads, solid roller etc. from a small tire street/strip setup, to a big tire (14x32) I found a fresh Dana 60 with Strange 35 spline axels and spool, Richmond 5.57 gear, ladder bar setup with new unused crossmember, shock mounts etc. everything with very little modification was what was needed to fit in my car and it all went together very well, with very little unforeseen problems. here's the question, doing the math, 1/8th mile car, trap speed @ 120 at 7,500, that gear would work, sometimes the drag race formulas are way to generic to cover every application. I was just told that with the torque of a bbf my car would work much better with a 4.30 or 4.56. my car weighs a little under 3K, has a C4, the converter stall is a little over 5K on the brake and my tire size again is 14 x 32. This is my first non street/strip car with no need to consider a compromise between streetability and track function. not doubting this persons knowledge who gave me this advice, but am looking for additional opinions and advice. Thanks as always for your help.

Can I ask why you switched to such a big tire? There are guys running in the 1/8 mile in the 4’s (maybe 3’s) on a 28X10.5 Those giant tires add a ton of unsprung weight. What is a safe max rpm for you’re engine combo? Have you had it on a dyno?

As for you’re question a 5.57 is probably a little steep and you may not get through the traps at 7500 when you figure in converter slip.

Double post

Can I ask why you switched to such a big tire? There are guys running in the 1/4 mile in the 6’s on a 28X10.5 Those giant tires add a ton of unsprung weight. What is a safe max rpm for you’re engine combo? Have you had it on a dyno?

As for you’re question a 5.57 is probably a little steep and you may not get through the traps at 7500 when you figure in converter slip.

Well..... I'm just going to toss this one in with the others, "Why'd you build an SN95 and not a Fox body?" or fill in the blank of what car that person thinks I should have built, "Why'd you go with a Dana 60 and not a 9 inch?" Why'd you use a C4 and not a powerglide/Turbo400/C6 etc. etc.?" pick one, or my all time favorite "why'd you put a carbureted, N/A, big block ford in it and not a fuel injected turbocharged LS motor?" Most of these are valid questions and can all be answered very simply; because it's my car and that's how I wanted to build it, that's the great thing about hot-rodding isn't it? my question was about gearing, not tire size, I am very aware of how much power can be put to the ground in a small tire car, but that's not what I was asking about. The gear was in the rear end when I bought it, it very well might not get through the lights at 7500..... but thank you for your reply.

If you're going to run it in the 1/8 mile, you should try the gear that's already in it first, and see what results you get.
You want it to be at or very near your max RPM at the finish line.
Obviously, if it's way over your intended RPMs, you'll need to reduce the gear ratio.

BBFTorino wrote:If you're going to run it in the 1/8 mile, you should try the gear that's already in it first, and see what results you get.
You want it to be at or very near your max RPM at the finish line.
Obviously, if it's way over your intended RPMs, you'll need to reduce the gear ratio.

Very good advice above IMO!!

Like has been said run it and see what it does that will tell you which way you need to go.

Big tires will slow you down, but can also make the car very consistent on crappy tracks.

Also IMO spinning the combo youve mentioned to 7500 is a waste of engine life, it’s not going to make power much above 6700-6900 and should have freight train torque. You’ll probably find a 4.56 or 4.88 better f oh r the 1/8.

Thanks for the great advice, much appreciated, test n tune is 2 weeks away, I'm taking it out to see what it does as is. If lower RPM is where it's pulling hardest (freight train torque) and I can go quicker only spinning it to under 7, even better. As far as the big tires making it consistent, that's more important to me than squeezing the last 10th out of it.

I ended up switching to a 4.88, it worked very well.