Hello my name is Jacob and i love my chevy's, and my current built i am doing i need some help. The project is a 1980 trans am.... with a chevy 355 and a super t ten. now my issue is that i was told that i am going to lose alot of horse with the rear end i am using, you know since i am not useing a pontiac motor. i was told that i would be better off with a early z28 rear end? the motor is dont have to many miles, rebuilt a few years ago and was real clean whan i put the HV oil pump on, also it has a hi flow water pump and a edelebrock preformer and carb i dont know yet. i do think it has a rv cam and not much else. now what can i do to get some pony. i am on a very tight budget but any input will be great, i figure i would get better advice here since i am builting a camaro clone and onec i get it done and then 4x4 i do plan to get another camaro.

 

for the whole rear thing and losing power u could just get new gears for the rear u hav

 

i never done a rear end only swaps

 

I and fairly sure the use the corp 10 bolt in that car I assume the early z rear you are talking about is the 12 bolt they are at premium prices. Dont discount the 10 bolt rear you have its a decent rear for moderate hp output.

 

all the pontiac guys say that pontiacs get there power from the torq and that my engine just isnt a good match for the rear end but that is just what i have heard

 

First off, A rear can not give or take HP or torque.Every engine had a torque curve (when its most power full) when you change the rear you are just deciding what is important to you. You can change you gears so you run a faster 1/4 mile but it will cost you top end. You can change them for 1/8 mile but it will cost you in the 1/4 mile.

First thing you need to do is figure out what rear end ratio you have. Jack up the back ofcar turn the drive shaftexactly one turn. Have a buddy watch the tire and see how many times the wheel goes around. It is most likely between 2.7 and 3.7 times. If only one tire turn you will have tospit you answer in half.

With that info plus you telling us what is important to you we can help. Gas mileage, top end, 1/4 mile or road racing?

 

I agree on knowing what gear you have first. Doesn't matter what rearend (axle) you have, it's the gearing that matters.
And not trying to bust Gorn's nuts, butit's the driveshaft that will be doing more spinning, not the tires. Rotate the tire one revolution, and count the number of times the driveshaft turns. Don't forget to put the trans in neutral too.
And whether you have an open diff or limited slip could make a difference in that procedure. You may then need to turn the drive shaft instead, and count how many shaft turns there are to one wheel rotation.

 

I want to have a respectable road racer that has good mpg 18+ i would be happy. I wont be racing it everyday, i want have about 300 - 400. The project is a budget built and i have most of the motor done. It is still on the stand but if there is anything i can do to the car to give me power i want to know .like i said i am very good with a wrench but this is my first time built up a motor.I have a friend that is building a z car and our motors are a close match, the stuff he has is all the porting and rebuilt heads and a Yenko intake, he knows his stuff for sure but when we race i want to show competition. i can get the rear end info as soon as you guys tell me what way you want me to check or do you want me to try both ways

 

Spin a tire and count the driveshaft revolutions, that will tell you the ratio.
In your last post you stated "road racing", is that what you are building for or 1/4 mile?
Also, you want to be competitive with your buddy's car but in comparing your engine to his you may be comparing apples to oranges. Heads, intake and carb are one thing but the internals mean a lot for horsepower. In short, don't expect a gear change to put you ahead or even close to beating him. To assemble a competitive car it takes a balance of horsepower, trans, gears and tires to get the power to the ground.

 

looks like 1 spin is three turns. I am not builting to do go and compete at the drag strip, i just want to built it to a drivable power house. i am going to drive it very ofen but if i feel the need to show some mustangs and rice burners that a muscle car is the best