Just curious if it would work, I found a thread about modifying a 12a header to fit a 13b but not the other way around.

 

Pretty sure it cannot.

In that thread they made the smaller 12a flange wider to fit the 13b.....going to be tough making a 13b flange narrower.

 

I have a roadrace 12a header

 

It depends on the header.

A large diameter, thickwall tube header (Racing Beat) or a factory manifold can be ported and the mounting holes ovalled. It's time consuming but trivial.

A thin tube header won't be as easy, unless it has a very thick flange.

 

Yes, it is pretty simple if it is a non-collected header. Cut the flange in the middle, remove 10mm. Cut the front tube about 1/2" away from the exit flange, remove 10mm from teh end of the tube and them weld it all together.

-billy

 

This is the one I'm looking at. Look like it might work? http://i72.photobucket.com/albums/i1...e/P5110333.jpg

 

yuck

 

How much for your 12a header then?

 

That is, again, waaaaay lots of work.

It's only 5mm of mismatch per port. That is less than 1/4". Most headers have almost that much port step-out to begin with, so it is trivial to open the inside (or outside) as necessary to ensure no improper mismatch. Slotting the holes poses no great risk to strength, either.

I really wish I could find the link, but it was really old and is probably gone by now, but there was an Australian site where they detailed how to turbocharge a 12A, using 13BT exhaust manifolds and a spacer so the turbo could clear the 12A intake manifold.

 

Yes peejay, we all understand your preferred method. Some of us prefer to handle it differently.

-billy