Gear Ratio ??

[Bad67MF]

I've got a 67 Fastback that seems a little lazy off the line.It has a 347, Edelbrock Alum. RPM heads w/2.02's & RPM int. w/650 Mighty Demon, 9.5:1 comp. Comp Cams XE274H, AOD w/2.84 low gear set, 3000 stall, 3.73-9" locker, 26" tall tires. The power band is between 1800-6000. What might be a better rear gear? Street driven mostly, been to the track a couple of times only on street tires. Run's 12.50's spinning the tires all the way down the 60' concrete launch pad.

 

[charlies]

if it seems lazy off the line, yet you are spinning tires you need better traction, not better gears. all steeper gears are going to do is make you spin worse.

if you get your traction problem fixed, the car in your sig could obviously handle 4.11's or it would be fine with 3.55's, it's all a matter of your preference.

 

[Bad67MF]

Maybe I should have said in normal driving conditions on the street it is lazy compaired to the 289 and C4 and 2.79 stock set up that used to be in the car. On the track it is also still lazy right off the line ( most likely the power band) it actually dosn't start spinning for about the first ten ft. or so. It dosen't blow the tires right at the hit of the throttle like the orig.set up used to. Just thought someone might have a simular set up and could give some advise on rear gear size. Thanks.

 

[D.Hearne]

I've got a 67 Fastback that seems a little lazy off the line.It has a 347, Edelbrock Alum. RPM heads w/2.02's & RPM int. w/650 Mighty Demon, 9.5:1 comp. Comp Cams XE274H, AOD w/2.84 low gear set, 3000 stall, 3.73-9" locker, 26" tall tires. The power band is between 1800-6000. What might be a better rear gear? Street driven mostly, been to the track a couple of times only on street tires. Run's 12.50's spinning the tires all the way down the 60' concrete launch pad.

It seems lazy to you off the line due to your combo. You have it built to make power in the upper rpm band. Only way to fix that is to put in a milder cam. Doing that will lower the power band but as charlies said, make your traction problems worse. You could also swap in a lower stall converter, that 3000 doesn't help either, sounds like too much stall for your combo. With those cubes, and even with the large flowing heads and cam that you have, combined with the low trans first gear, the rear gear and tire combo, you really don't need that high a stall converter.

 

[Bad67MF]

It seems lazy to you off the line due to your combo. You have it built to make power in the upper rpm band. Only way to fix that is to put in a milder cam. Doing that will lower the power band but as charlies said, make your traction problems worse. You could also swap in a lower stall converter, that 3000 doesn't help either, sounds like too much stall for your combo. With those cubes, and even with the large flowing heads and cam that you have, combined with the low trans first gear, the rear gear and tire combo, you really don't need that high a stall converter.

I can live with the combo on the street, it's fun when the other person get's you off the line then you go screaming past him on the top end. I know at the track I need slicks. With my combo I guess I should put in a trans brake and just try to launch the car aruond 3000rpm? And hope it hooks up and does'nt break anything. P.S. I don't condone street racing!