im about to purchase a friends comptech 4-2-1 header which is currently on his 99 civic si. the part numbers online are different. I know that the header will bolt up to the motor as it is a B series, and the flange size listed is 2" for both the ITR and the si header.

I called comptech but did not get good help. I was told that they "think" the si header is a little longer and I would have to get a custom test pipe. Emissions are not a concern here, so I could do that.


Summary : will this header bolt up directly ? if not, is all I need a test pipe ? Lower mounting points and O2 bung in same spot ?

- kevin

 

It may be tight at the oil pan (due to the B16A's shorter deck height), but it is the same overall length to the cat. However, the collector flange is oriented at a different angle on the Si than it is on the ITR, so you would need either an Si cat or a custom unit to do the installation.

 

you say it might be tight at the oil pan... does that mean that it will just be a pain to install or that I should not even buy it and try to install it ?

 

I unfortunately don't know how tight the Comptech piece would be, and unless it's a tremendous deal, there are probably better-performing options in the same general price range.

 

When I have installed my Comptech Header on to my Civic with ITR Rngine it was a VERY Tight fit. I have to move it around for to make it fit, I think it took my quite sometime to align it correctly.

BTW: I bought a used ITR Cat. to connect to the header and it was a Perfect Fit.

VERY close to the oil pan, if the Si Header is even closer to the Oil Pan, I do not think it will fit.