455... Help

[fatso86]

i have 1970 455 buick .30 over with ported heads and headers... about 400hp 510lbs of torque
im putting it in 1988 cutlass supreme
i dont know if i should use a th350 or th400 and dont know what gears i was thinking like 3.73 with 10 bolt rearend from a buick gn...

THANKS FOR THE HELP...

 

[dogsht]

How are you going to use the car? Slicks? 1/8 mile, 1/4 mile, drag radials and stop light to stop light?

 

[DRIVEN]

^^All valid questions.^^ Transmission selection is up to you and they'll both work fine. A TH350 is more efficient but will need stronger parts to live a long life. The TH400 is obviously stronger but it's also heavier and uses more HP to operate. Also this:
http://www.angelfire.com/fl/procrastination/rear.html
Unless you will be at the track alot, I wouldn't get greedy with the gearing. You'll have plenty of torque for 3.08 or 3.23s.

 

[Intragration]

Interesting combo. You didn't give details on your intended usage, that would help. My observations are, the 350 should probably hold up ok, G-bodies are pretty light. The 10-bolt isn't a bad idea if you can find one and can afford it. If you do find one, it may be economical to replacing gears in the 7.5, you may fix up the 7.5 and blow it up anyway. As for gears, I would say 3.73 would be more for if it's going to be a race car and limited street car. If you're looking for more street fun with a bit of highway, I'd say you'd be better off with something in the 3.08-3.42 range. Don't underestimate 510 lbs of torque....or the fact that a big block doesn't need to rev like a small block.

 

[G-Body_Vet]

If you're putting together a daily driver-type car I wouldn't go any higher than a 3.08 with a 3 speed trans. Cruising at 65mph w/3.73's and a 3 speed is miserable.

I view an OD trans as a must with low geared street cars.....but that's me. If I lived in a podunk town it would be one thing, but expressway driving is a must where I live.

 

[dogsht]

I agree if you are gearing it for the best quarter-mile AND you want to be able to use it as a real driver as in more than just a stop lighter then the extra coin for an overdrive is well spent. Probably the single best upgrade you can make for that type of car. If that is the case leave the three speed in the 70s. If you are willing to settle for a good compramise of decent acceleration and decent driveablity using a three speed than 3.08s or 3.23s with 28 tall tires would be the best gear for behind the 455.