Howdy! I have been reading this forum for some time but have just now joined. Have a question. I have a 89 IROC that I swapped in a 454 mpfi with 4l80e trans. It works great! Now I must iron out some kinks. One in particular is the exhaust. I used some swap headers that I bought used. Dont know what brand they are. They hit the frame, the floor. all sorts of things. I thought I read somewhere that a particular model of factory manifolds would work. Anybody know which manifolds will work without touching anything?????? Any help will be appreciated. Thanks.

 

Welcome to TGO

There are no factory manifolds that will work any better than the swap headers you already have. The swap headers are the cheapest exhaust you can get and are also the worst fitting. Chances are if you manage to trial fit a lot of different cast manifolds, finding a set that would work will probably cost you more than the swap headers. The cast manifolds are very expensive. Finding a used set that are not cracked or warped may take a long time.

The best fitting headers are a set that are custom built to fit your application. Unfortunately, this also isn't an inexpensive option.

 

Exhaust manifolds from the 8100 Chevy truck.

There is a thread about a guy who used them. Look in either the

Exhaust
Or
Engine swap

threads.