I just picked up a complete 12A exhaust system for a decent price. How hard is it to enlarge the holes to fit my 85 SE's 13B block?

Is this reliable or will the header crack?

 

try it and see. if it cracks get it wleded and sell it.

 

I'm going to say use some common sense on this one.

 

cut the flange in half and seperate the two pipes.

 

Huh? I thought this was a legitimate question. What is your point here? If it can't be done, say so.

Thanks.

 

in my OPINION, don't do it.
the racing beat units are engineered preciesly for the engine they are going on.

However you could probably get it modified to fit and work just fine. Just may not be optimal.

It seems to me it would be like getting headers for a small block v6 and "modfying" them to work on a big block v6.... just wouldnt really work right.... exhaust flow and dynamics could be seriously off... however it may be just fine on the rotary. I donno!

 

What you should do is sell the 12A header on E-bay and then use the funds to purchase a 13B header. There's really no point to modifying the 12A header when you can get the right part so easily...

 

Here's what I hear that people do when they want to do that either because they don't feel like buying a brand new header or whatever. they cut the flange in half and double up on the gasket. Seem to work for them. Try it, if it doesn't you still have a good header and nothing is lost.

 

I think Moses idea makes sense. It will not cost you much and you will end up with the right parts. Better to do it right once, then wrong a couple times.

 

This is why I said use commone sense. I always say do the job right the first time around.

 

I have a 12a header that was cut and streched to fit a 13b. even though it was done very well it broke after a few years and had to be redone. The guy was a welder for it did not cost any extra.

If you have a welder and torch, I say go for it. If not I would sell it and get the correct header.

 

'73 12A header slotted to fit a '74 13B. Figure that one out if you can.