Gear Ratio

[396chevelle]

I am running a NA BBC 468 I plan on running about 140 mph. I am running a 29.5 tall tire. The cam and cylinder head combo should make power from 5000 to 7800. Stall rpm should be about 5500. This is a heavy car about 3400 race weight. Should I lug the motor with a 4.56? or do I spin the snot out of it with a 4.88?

4.88 @140 =7800 rpm
4.56 @140 =7200 rpm

I probably should add a couple hundred rpms for convertor slippage.

Thanks Cary

[jsj372]

On a BBC I don't think you will see an improvement going from 4.56 to 4.88. I would use the 4.56 just so your not beating the engine up. I bet the car will run same number or close if you run it at 7200 or 7800.

[396chevelle]

jsj323
Thanks for the info.

kind of suprised only one response. No one else has an opinion

[Jim Monson]

I would spin a N/A combo vs lug it down.