What size headers?

I'm buying headers for my 91 gt. I have an off-road h-pipe and flowmaster 40 series. I can't decide if I shoud get 1 1/2 inch or 1 5/8 inch headers. Any suggestions?

What have you done to the car for mods? 1 1/2 might be better off for a stock car. It would help retain or gain some low-end torque, where a stock motor needs it. 1 5/8's might lose some low end torque, but pick up higher rpm HP. I have been running 1 5/8's since my car was stock and it seemed to run well. If your planning on adding more mods I would get 1 5/8's. Just don't get 1 3/4's, that would be too much, unless your pushing out serious power.

I only have the off-road h-pipe and the mufflers. I'm graduating so I'm buying headers, cold air intake, and a Pro-5.0 shifter with some of the money I'm getting.

what about if all you intend to do to your engine is normal aspiration, with a new set of heads, pullys, 24 lb fule injectors and new intake and exaust systems? I can't decide if these mods will qualify for heavily modded or not.

1 5/8ths would be best for a near stock car. If you're doing heavy power like 400+ like with new heads or SC, then yeah, maybe a 1 3/4 might be good for you. As far as I know, 1 5/8th LTs are pretty sweet on near stock cars.

:D