Hey everybody, i just got done building a new rear axle for my '67 Skylark. Right now it has 2.56's with an open carrier, and has run a best of 10.67 in the eighth. I built another 10 bolt with 3.55 gears and an eaton posi. Taking nothing into consideration but the gears, what kind of E.T. gain can I expect? I figure that it would be the same for any car, but what do i know anyway?o No: Anyway, thanks for your help. -Clay
Post up the rest of your combo. The main goal of a gear swap is to allow the engine to operate in the range where it makes the most power. You'll definitely pick up out of the hole if you can hook it, what engine mods are done?
I think Bobc455 has good info on this. I think he went from 2.56s to 3 somethings and saw no astounding gain.
The less torque your engine makes the more gain you'll see. That's why Bob saw little change. You should improve the 60', and most likely some improvement in the 1/8th. If you're rpm limited (as in head flow, camshaft or valvesprings) you may not see much change.
My 71 GS455, with 3.42's and an Eaton posi was pretty consistent around a 1.9 60 ft. With a more powerful motor, my 72 Skylark with an open 2.56 rear (and the same Hoosier Quick Time Pros) went a 2.30 60 ft time. The GS455 had a stock converter in the TH400 and the Skylark had about a 2600 rpm stall in a TH350.
My engine is a 10:1 350 with a Poston GS114 camshaft with 480 lift. I am running the stock Iron intake with a modified quadrajet and exhaust manifolds. It pulls hard from 2500 all the way up to 5000. I was just looking for a way to get the engine through its powerband quicker. I saw a big change when I switched the old 2 speed transmission for a Turbo 350, and I think that these gears will make a much bigger difference in take-off than even the new transmission did. I just need to find some time to put the new axle in. Thanks a lot, Clay PS: I have 205's on both the front and rear. Yes, I need traction, even with the 2.56's!I think that some good tires and this new gearset will buy me more than just a couple of tenths. I haven't yet made a run where I didn't spin the tires for at least half a second. I just spent all of my money on other performance stuff and now I have no money to buy some good wheels and tires! Ah, the woes of being poor...
