What is the best way to get an overdrive auto in a 67 Barracuda?
That's a ton of info, going to have to examine that closer after work tomorrow, my next question was answered, the weight difference which is signifigant. I need at least a 2800 rpm stall, I'm running a 440 with a 727 and 355 gears, I ran a 12.40 in the quarter blowing the nitto drag radials off at the line and with some bad high rpm breakup issues, car was going through the finish line at 6700. Cruising down the road it's around 3600 at 55 mph. Very uncomfortable. I appreciate the information.
I can assure you the numbers I gave are pretty close, my rear tires are 245/45/17 which is around a 26 inch tall tire. Cruising down the road it's at 36 not 26 at 55, maybe going 60 but no faster, I have mini vans passing me for pete sake. It has been a couple months since I drove the car but I know the rpms are over 3000 at rural highway speed. If I was at 2600 rpm I would not be looking at overdrives. I would be tickled if my rpms were 2600 cruising the country. Unless I have an imposter for a rear gear, I'm almost certain it's a 355, my dart had a 440 with 410 rear with the same tires and that was like driving a tractor down the road.
I know you hate math, but;
a 12.4second car should go about 107mph.
107 with 3.55s and a 727 and 26 inch tires is; wait for it ;4910 in direct with zero slip, and it is 7120 in second, with zero slip.That's just simple math;and math don't lie. If you add say 6% for slip the rpms are 5205 and 7547. You said 6700, so that would mean that you are not in second. Ergo you must be in direct. 6700/4910=36.4561% slip
I can only conclude that: A) your TC is junk, or B) your tranny is junk,or C) Your tires are not 26,or D) your rear gears are not 3.55s. Those are the only variables in the equation .
So since it appears you are confident that the TC and tranny are OK, and that the tires are 26; that kindof leaves no option but the gears.
Sooooooooo,what might your rear gears actually be? Well,
Here's more stinking math;
6700 @107, with say 6% slip is about oh lemmee see; I get 4.56871
So of course you might need an overdrive, cuz, oh-oh here comes more stinking math;
lemmee see 65 = 3800 no slip, perhaps 4024 @5% slip.The formula is in post #61, right at the top.
This is like grade 8 math.
I drove 3.55s for about a Zillion miles.With 245/60-14s, no less. And 60mph(Canadian speed-limit) was about 2785rpm.I usually cruised at 56/2600rpm.
Overdrive options have already been discussed.
