Gear ratio question

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Mopower71

Mopower71

Speed Demon
Joined
May 31, 2004
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Poughkeepsie, N.Y.
I need a recomendation on which gears to put in the Demon.
Last time out with the car I was shifting at 6800 rpm, but crossing the line at around 6200rpm.
340, 13-1comp, .530 solid cam,850 holley,
4500 converter, 4:10 gears, 27.8"tires (325x50x15's)
Should I go with the 4:88's, the 4:56's or stay with the 4:10's.
I have all three. the 4:10's are on a spool and the other's are limited slip.
Suggestions,comments? :-k
 
or try an inch shorter tire.....you MIGHT be able to borrow some from someone to make a run or two to see.....
 
Have you tried shifting at a lower rpm ? I only ask because if you are not still making good power at 6800 rpm you may go faster dropping your shift rpm and not need as much gear. If not then you definetly should go faster with more gear. But like alot of drag racing its trail and error. If you still drive it on the street I would try to stay down on the gear as low (# wise) as you can and use the shorter tire at the track as you can go to a taller tire for street cruisin. Ron
 
I think your answer depends on the engine..What rpm is you peak torque? What are the rest of the cam specs? Just looking at what you listed, I'd say you have some convertor slippage issues. What is your trap speed?
 
Well, if he spins 6800, that's bad..With zero slip, 4.10s, and 28" tires, he should be turning 5500. Now, no auto convertor has zero slip..say, 4-7% is acceptable..He's got 13% slippage, even with subtracting the 4-7 spec. (came out to 20% between rpm levels). That's terrible. A low gear set MAY help this, but I doubt it. You can try 4.56s..You should go faster, but I dont think you trap rpm will change much..You can add gear, but the convertor will be doing nothing more than making heat at the high end. Harness the torque the engine is making.

(sound familiar mike?) :afro:
 
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