k so i did a lil measuring today bc this has been buggin the hell outa me. the header on my ls vtec is the after market one from my old bolt on ls setup. its 4-2-1 and surprisingly gave the ls motor a kick in the pants over the 4-1 header i had b4 it. anyways i transfered it to my ls vtec setup n was wondering if it was robbin me of power over other b sereis vtec headers n this is what i found when measuring today.

the primaries on the non vtec header are 1 1/2" . the typical aftermarket b sereis vtec header has primarys that are 1 3/4" (thanks to a lil chat i had with john at lht about them). b sereis vtec race headers have primaries that are 1 7/8 " . so if anyone was wondering, YES there is a difference in the headers. also to be noted, some headers come with different size collectors (2.0" is usually the size to fit a stock cat). some of the better headers come with 2.5" collectors however. just thought id share with every one!!! i guess i can safely say that i definately am being robbed of some power up top, however i believe this makes a bit more tq due to the smaller primarys (correct me if im wrong). anyways...enjoy!

 

i was running the comptech 4-2-1 header on my ls/vtec and felt a nice difference through the entire powerband with the JDM ITR header. my motor likes the 4-1 better

 

<<i know someone that newthis..but good info i like 4-2-1 myself

 

im still debating on what to get. either way im gettin a header made for vtec. im leaning towards the 4-1, but then ill have to get a skid plade made so i dont smash it lol.

 

honda makes an OEM skidplate for the header

 

haha yea but oem honda headers ae EXPENSIVE!! lol a buddy of myne just got an ebay knock off for like 100 bux in stainless steel. i think i might get that (i kno u die hard jdm ppl out there arent gonna like it), n break out the ole welder n fab up a skid plate from some sheet metal n tac weld it on. not sure yet, all i kno is i want/need a better header so thats the next mod.

 

If someone has a suitable car, a few quality headers and someone who wants to donate labor we can do a dyno comparison. I think Bert-O or someone did a comparison a couple years ago

 

ill donate my car!!!! anyone wanna loan a header?

 

I'll donate my 4-1 JDM ITR, if you need it for tests!

 

YES! lol lets do it!