what gearing for 1/4 mile

[tim]

Hello there, I have 73 barracuda, 340 done up with 727 auto. for the first time ever an airport is being rented for 1/4 mile drags in Port Alberni on Vancouver Island. Right know I,m using 3.91,s on my car but a freind has given me a set of 4.13,s for that weekend. My question is , will that be a good gear to use for 1/4 mile? or is that a gear that one should use for 1/8 of a mile. I,m not sure if it,s gonna be set up as open street or some sort of bracket, but it doesn,t matter does it, one pass will be great,lol. I know my car is making horse power at like 6000 rpm, maybe even higher as I,ve taken it to 6500 with no problems and it,s still pulling , also I will be running 15 by 26 hoosier slicks on the rear. Thanks Tim

[DartMan360]

If your making power up in the RPM range than go to the 4.13's. It will help you get off the line. They might rob you of a couple mph but not many. Something like this I tell people its just somthing you have to try. But like you said its for one day only.

[mr_340]

You might check those gears again. Are they 4.10s or 5.13s? 4.10s should work pretty good on the 1/4 mile, and 5.13s would be great for the 1/8th mile. Try the following formula:

MPH=RPM*TIRE DIA./(GEAR RATIO*355)

Use 340 instead of 355 if you have a manual transmission. This difference allows for the slippage of the converter.

[goose]

The main goal when gearing your car for the dragstrip is to have it reach redline in top gear right as you cross the finish line. The best way to do this is to take your car on a couple passes and figure out what MPH you are hitting across the finish line, then gear the car as I have described. Use the formula from mr_340 to calculate your "best" rear end ratio once you know the MPH your car will hit in the 1/4 (or 1/8).

[Darn Dart]

I don't think you would gain anything by going from 3.91's to 4.10's. Since you have a fairly short tire anyway (26")