'81Z28

Im in need of some guidance, Ive got a 1979 camaro with a built 355, dynoed at 427HP, 450TQ. The car has 3.08 open rear end, and to say the least the car is not exactly impressive from a dead stop flooring it. But going down the highway doing 65-70 and floor it, it climbs quick, real quick. Its also got a 3200 stall converter in the turbo 350 trans. I'm wanting to have it throw you back in the seat and hold you there. I also have a '81 Z28 that we're restoring that has 3.73 posi, thinking of swapping out the rear ends just to see what kind of difference it'll make. any advice is appreciated.

Injuneer

The ultimate mod would be a 4.11:1 rear gear, Eaton HD limited slip, and a Gear Vendors (GV) O/D (0.78:1) unit on the tailshaft of the TH350. The alternative to the GV would be conversion to a built 700R4, providing an 0.70:1 O/D. The GV unit is expensive though.

Gear Vendors under/overdrive transmissions the most awarded auxiliary transmissions.

The 4.11's will increase the torque at the rear wheels by 38% (of course you will hit redline at 38% lower MPH in each gear, but now you have 4 gears - or actually a 6-speed if you split-shift the GV). The 0.78 O/D ratio of the Gear Vendors unit will allow you to cruise almost as if you had 3.23's. The 0.70 O/D ratio of the 700R4 will allow you to cruise almost as if you had 2.73's. Without the GV unit, or a conversion to a 700R4, the rev's will drive you crazy on the freeway.

If you opt for 3.73 gears, you will see an increase of 21% torque as the rear wheels. The GV O/D will cruise like it has a 2.90 rear, and the 700R4 will cruise like it has a 2.61 rear.

I have a 500 (flywheel HP 383), through a TH400, GV and a set of 4.11 gears. It will roast the 315 drag radials in any gear on the street.

'81Z28

Thank you very much for the reply. A lot of knowledge there, and it is appreciated. This car doesn't get driven much more than about an hour at a time maybe twice a week if that. We're more of hot shotting around town in the car or tearing up some back roads. We may just leave it as it is, and build the '81 as the 1/4 mile car and leave the '79 as the cruiser. But like I said the '79 is powerful, just not what we expected from a dead stop... I'll get all of the documentation on the engine and post it soon. Another issue we're having is with the big cam, we're not so great on vaccum so the PB are a little soft. Any remedy for that other than a canister or electric vac pump? What would you recommend? Thank you again for the response, very much appreciated.

FirstYrLS1Z

the 79s' and 81s' had the same rears,so interchanging should not be a problem. As stated above,a 21% increase in torque to rear wheels,so that 450 torque will feel like 544 torque.

Chimera96

that kind of HP with a high stall BUT those hig 3:08's are just killing your off the line pull...as you know

with the turbo 350 3:73 gears are "tolerable" in terms of FWY driving....but sounds like that is not the primary use so I would do 3:73's with a Eaton 400 lb LS diff

even 3:55's would be better if you wanted some improvement

GV set ups are cool but $

or convert to a T56 with 4:10's :-)