Auto Racing: Proper rear end gearing, torque curve, tire diameter

Question
I don't street race.

Dan my question is about gearing. I'm setting up a bracket car and I've built my engine to max rpm at 8000 rpm. I want to run quarter mile, it now has a 3.23 rear end ratio. Dan I have a 4 speed stand Transmission, what gearing would you recomend?

I have considered a 4.56 or 4.88

Answer
Hi Walt.

Since it's a bracket car, your absolute final time isn't as important as getting there every time. Use the higher of the two , the 4.56.  That way you won't be gear limited at the traps. If you decide to switch to the head on foremat, go for the 4.88.

Of course, your rear tire diameter and max engine RPM are factors to be considered. Also where in the RPM range does the horsepower occur, and where does the torque curve begin ?   

And finally, the internal gearing of the tranny will make a difference too. If it is a close ratio racing box, so much the better.  BUT in you have to shift more than twice in a pass, you're wasting WAY to much of yout ET shifting gears.

Before you fork over the bucks for the stump puller gear though, get a positraction unit to go with it. And after that, consider that a little wheelspin coming out of the hole isn't all bad, you'll spend less on drive train repairs than the guy who is greared to the ground.

Hope this is a help. Understand that I won my last drag race by anticipating the FLAG MAN !!  How long ago was THAT !?!

Good luck

Dan Liddy
Sarasota, Florida