Planning my build

[David]

Although some of this might be better suited for the transaxle section, I'll post it here. I plan on useing a crate 331 from Blueprint engines, rated @ 375 with 390 Tq. The roller cam they use is on 112* seperation, so not very lumpy sounding. This is a carbed engine and that is fine with me.

I hope to use a Griffin (sp) 5 spd transaxle. I think a 3.55 rear gear, with the optional 2.20 1st gear and the 0.61 5th should make a decent driver. Would I be better off with a 2.4 1st gear, or a 3.7 rear gear, rather than my choice. My plan is not to build a race car, but meerly a driver, as we travel light. Thanks, David :undecided:

 

[John]

David FWIW I think personally the 2.2 1st with the 3.5 final would be better as a touring car, and unless your heading into the mountains , you wont have any troubles with pulling from rest with 375 HP with that combo.
good luck with the build.

cheers John

 

[Howard Jones]

Stay with the 3.55 final. As far as 1st goes, you will only use it for traffic jam diving, getting on the trailer, and leaving stop lights. I have a small diameter custom made Renault origin size clutch in a R21 with a lot of custom gears in it and a 2.3 1st/3.44 final. The clutch is pretty much on/off and takes a bit of commitment to leave from a stop. I would prefer a lower 1st for trailer mounting and stop lights.

If I had to choose I would go with the 2.4 1st and the 3.55 final. Then about 1.7 2nd, 1.3 3rd, 1 to 1 4th, and about .7 5th, with a 3.55 final.

Do a speed/rev chart. I like about 2700 @ 80MPH in 5th for cursing. Then a dip down to 4th and the thing pulls like a freight train all the way to 140ish. I never use 2nd on track. These cars are so light and have so much grip that unless you have a complete U turn on your local track, 3rd will pull plenty hard off the slowest corner and you can leave out the extra shift in and out of second and not really effect lap times.

Good on you for really thinking about gear ratios. The best way to screw up and nice hot rod is to get the gearing wrong.

Oh..........don't forget the limited slip! This is a MUST have IMHO. I like my Quaife so much in my GT40 that I put one in the SLC I'm building.

 

[Jack]

Ditto Howard's comments!

 

[David]

I ran a 68 Mustang with built 289 for years. I had a close ratio ( 2.20 ) 1st with 3.55s, it worked well. Well except 3000 rpm @ 60mph, sucked down the interstate. A
ll my cars have a limited slip, Trac-Loc, Torsen, or some type of non open rear.
Being that the 5th gear ratio is .61, having a 3.79 rear might be better. With that staying with the 2.20 1st.
Enjoying reading Ya'lls builds. David

 

[David]

I have a Monster Miata ( 90 5.O HO ), with T5 and 3.27 Traction-Loc. Cruiseing @ 60mph, its only turning ~1800rpms. So the taller tires on the GT40 coupled with a 3.55 may well be ~2000rpm. Great for MPG, not much power though at that low of rpm. I've learned a long time ago, just because you have a 5th gear doesn't mean Ya cann't drive it in 4th, and downshifts are easy.