I wanna run a 4-1 header from DC or something but I don't know what size collector to get with it. I plan on having a Hi-flo cat and cat-back exhaust soon afterward.

Also, whats a good size exhaust to run an all motor application well? Im thinkin a solid 2.25 from collector-back. Thats why i need to know what size collector to use and what size exhaust runs well. Most ill prob do is I/H/E, stage 2 cams, itr pistons, match port, etc. thanks

 

with your future plans i'd go with their jdm 4-1 version with 2.5'' collector. but that header has suckass ground clearence. keep the rest of the exhaust 2.5'' as well to avoid bottlenecks.

 

2.5 is not too big? Won't be squeezing all the time.

 

2.5 is not too big, but if I stand corrected a 2.5 collector on the header where it connects to the cat will have to be altered to fit. If you go w/the standard fitment and a 2.25 exhaust, you should be just fine as well. Maybe a 1-3 hp gain with the other set up, but don't quote me on that, it is not big power.

 

2.5'' is about the max you would want to go on most NA setups. now if you really got crazy with the build, big bore big stroke etc., then stepping up to 2.75'' or even 3'' would yield some gains.