subtlez28

I'm building a stripped down 84 C4, and swapping in an LS1/T56. It is intended for the road course. My weight goal is under 3k lbs w me in it and around 400 hp (LS6 heads/cam).

Details here:
http://forums.corvetteforum.com/c4-t...s1-t56-c4.html

I already picked up a 3.45 geared D44. However, recent standing mile and open road racing threads have me considering a 3.08.

Also, at my local road course (Blackhawk Farms), my 02 Z28 runs 3rd gear most of the track (with an LS1/T56 and 3.42s). I run into the rev limiter in 3rd in a couple spots, barely worth the time to upshift, then down shift again. I've always kind of wished I had maybe 3.23s or something.

Anyway, the vette should be lighter, better suspended, have more hp, and run bigger tires. So, I think the problem will be worse (the vette will be faster). My thought is less shifting the better. If I can hold 3rd most of the track, life should be easier, right? And if I run bigger tracks (like Road America) I should be able to stay away from overdrive more.

And with my new open road or standing mile goal (probably a couple years down the road)...

Will 3.08s work out better? Will I lose out on a lot of acceleration?

In running the gear calculator:
3.45s, w 25.68" tire, at 6000 rpm will give me
102 mph in 3rd, 132 4th, and 177 5th (mathematically anyway)

3.08s, w 25.68" tire, at 6000 rpm will yield
114 mph in 3rd, 148 in 4th, and 198 in 5th (again mathematically speaking)

Aardwolf

I run Road America a lot and you would definitely be over 132 MPH on the three straights. I would think you would be okay staying in fourth with the 3.08 rear and probably going a little over six grand. I'm not certain that you would exceed 150 MPH but there would be a little RPM cushion if so. I have kept the 3.08 rear gears on my car just so I wouldn't have to use fourth in the auto. Less high RPM shifting is very good.

At BHF I can't remember for sure but I thought I only did 110 MPH on the front straight and less on the back.

There is a procedure for choosing gears and I can't remember all of it. I don't think you would lose any acceleration if you have a broad power band. If you have a peaky power band then you would want your gears to keep your RPM high and in a narrow spot.

stairman

Stock C5 runs 3:42, why stop at 6K run it on up 7.2K

subtlez28

My Z28 sees somewhere in the 110-115 MPH range at the end of the main straight at BHF, and I need 4th on the other straight also, though I am to busy w the kink and hard 90 corner to look and see mph. I expect the Vette to be faster.

I want to choose a well rounded gear so I can have fun at multiple tracks and multiple forms of racing (road course, lot auto-x, drag racing, and hopefully open road racing one day). I don't want to choose a gear for one track.
Another guy I race w has a similar opinion. I say RPM cost money. I'm willing to give up a tenth or two to not need to replace an engine. It was a sad day when said guys 383 LS1 let go (though it was not on the track). I just want to buy things like engines once...

I did my figuring at 6000 rpm. He said:
"I have the limiter set at 6800 and don't have any issues with the z06 springs. Its just for the few times I need the extra rpm in a corner. I shift around 6200 on the straights."
I think I will set my rev limiter at ~6500 rpm. I plan on running stock LS6 heads and cam on my LS1. I'll have upgraded valve springs and rod bolts though.

subtlez28

TTT

I'd love to hear more opinions. Anyone running a 3.08 w a 4+3 o other manual?