Does it ever work? My friend has a header he wants to sell to me that he had on his FC, that he claims is a 12a header because it has smaller port sizes than the 13b. Are the headers transferable from motor-motor??

thanks, Colby

 

Kinda...

If you cut the flange or have a header that the flanges are separate already. You can just cut the flange where it bolts to the exhaust if its a true dual. Or bend the pipes out to fit.

The only real difference besides pipe diameter is the distance between the ports. Obviously the 13b ports are further apart...

 

no, buy the right header......better yet...I put the bonez downpipe on my 83 and it was great, perfect fit and cheap too!

 

It works. The RB header I have on my 12a right now used to be on a 13b, hence the gap in the center between the pipes. Pretty sure the pipe diameter is the same. I think it would be better just to buy the 12a header though. They're pretty cheap and you won't have to go through all the pain and cussing while trying to get all the bolt holes to line up just right.

 

#@!%?@%!/@#........https://www.rx7club.com/showthread.p...+Header+13b%3F..

 

As others have suggested; you can (provided you have half way decent fabricating skills and access to decent welding/cutting equipment). I however would not. Run the right parts for your motor just to be safe. That will be one less thing to go wrong.

 

If it came off an FC, chances are it's a 13B header. FC's never came with 12A's and not too many people put 12A's in them.

 

well he says the ad he bought the header off said it was for a 12a. Im going to do a test fit, if it bolts up.. ill use it lol.

 

alright so here is the deal. Header is in fact a 12a header. That has a 13b engine to header flange welded on and the rear pip has been shortened. So all i need to do is, cut 10mm out of flange, and either extend rear pipe, or shorten front pipe. whatever proves to be easiest at the time. Correct me if i am wrong all you smart rotary people!

 

Or you can do what I did and oval the holes ~5mm outwards and touch up the flange a little to prevent a step-in style mismatch. Every 13B I've ever run has used the same 12A header.

Neat thing about doing it that way, you can jump back and forth between 12A and 13B without any difficulty. When I pull engines, I unbolt the header from the engine and leave the entire exhaust system in the car.

The DIFFICULTY was that the header I used has a big plate for a flange and it interfered with the passenger side motor mount boss on the GSL-SE engine I originally used, so I had to perform some cuttery. I don't know what application actually used that boss, but it sure came in useful when putting another -SE engine on an FC subframe.

 

The header primaries are the same for 12a and 13b, both are 2" OD. The only real difference is the flange. I'm actually finishing up an s4 13b swap in my S2 and am working on a budget, so I cut off the collector and split the flange in half of an old 12a header I had, so I can use it on my 13b. Welded individual flanges on each runner so I can run dual exhaust back to the axle

 

Do you by chance have any pictures of what you did?

 

Like that?

 

pic isnt working :/

 

Header is on. yay