LS3 header primary diameter

[65 drop top]

I just found out that AME offers 2 different header primary sizes for my car, 1 3/4" or 1 7/8". Engine is a crate LS3 525. It's going to be a street car. I know the pro's and con's of using the different size primaries, just not sure which would be better suited for the LS3 525. I was planning on using 3" dual exhaust based on a poll I took on another thread which 66% voted for 3".

[coby74]

I have the same engine with 1 3/4" at first, talked to tuner pat g. about 1 7/8" and he said the 1 7/8" will make more power everywhere. After driving with both too me the engine had more throttle response with 1 3/4" and pulled more after 5000 rpm with 1 7/8". My first exhaust was 3 inch all the way to the rear then switched to 2.5 tail pipes after the axle with no noticeable loss of power.

[65 drop top]

Thanks for the info! So if you had to do it over again which headers would you go with, now that you have driven it both ways?

Mine is going in a 55 Chevy with a T-56 close ratio with 3.70 rear gears, if that makes any difference.

I have the same engine with 1 3/4" at first, talked to tuner pat g. about 1 7/8" and he said the 1 7/8" will make more power everywhere. After driving with both too me the engine had more throttle response with 1 3/4" and pulled more after 5000 rpm with 1 7/8". My first exhaust was 3 inch all the way to the rear then switched to 2.5 tail pipes after the axle with no noticeable loss of power.

[coby74]

I think I would of went with the 1 7/8". I changed out the dougs 1 3/4" because the were too close to the frame and touching in one place. The engine is in a 82 c10.

[Schwartz Performance]

I'd go with the 1 7/8. If you said you had a stock 430hp then I'd have said the 1.75".

-Dale