Ehaust manifold swap crap. what is going on?

[Doubt_Incarnate]

in swapping motors i was told the exhaust manifold from a gp wouldnt work in my j-body. that i needed the j body specif rear exhaust manifold.

i bought one. but it looks identical to the w body exhaust manifold.
what casting # am i looking for? i mean it looks exactly identical, but the part was sold to me as off a 89 z24. i saw a pic of the car (ebay), im certain its not a W car.

[sharkey]

RE: Ehaust manifold swap crap. what is going on?

there are 2 differnt styles of gen 2 exaust manifolds, the ones with a bolt on crossover pipe, and the 1 peice front and rear manifolds. the manifolds themselves are the same except for the crossover pipe. this is for all gen 2 2.8 and 3.1l motors.

now a grand prix manifold would work fine, as long as it had a 2.8l or 3.1l. if the manifold was off a 3x00 or 3800, it wouldnt work.

[Doubt_Incarnate]

ok, so i just spent 40 bucks for a big rusty paper weight?

not to mention wasted all that time. i'll turn it around and sell it on ebay i guess.

wish i could remember who told me this lie, been a while since ive been shooting...

[Guest]

Umm, there is actually at least two different rear manifold designs.

The J/L/N body type is where the down pipe flang is between the number 3 and 5 cylinders, the other type, most commonly found on the W-body has the down pipe flage rearward of cyl number 5.

Also, that one piece front manifold/crossover pipe was only used in 1988.

[sharkey]

hmmmm, interesting. i helped drop a 2.8l from an 89 grand prix into an 87 cavalier and the rear exaust manifold was the same. we used it because we wanted to get rid of the 1 peice manifold that was stock on the 87 motor.

[Doubt_Incarnate]

i stared at them, they are identical for as far as i can tell, both have the flange between 3 and 5. the donor car was a 91GP, transplant recipient is my 86 J. i know it inst a jbody motor for sure, because it had the dogbone towers on it, and ive been told over and over agian j's dont have that. i'll have to go look under the hood of my car and see how things sit there.

[Doubt_Incarnate]

i looked under the hood. it looks like my exhaust exits between 3 and 5, but the angle looks to be quite a bit different, at least from the angle i saw it at. i guess worst case senario i get to try to make a new downpipe.

[Guest]

Yeah you will have to make/get a new down pipe.

Not all W-bodies used that other manifold, I know there are pics around here somewhere of it.

[sharkey]

my 86 z24 has the exit between 3 and 5. as long as what you got exits between 3 and 5 it will all bolt right up.

[Doubt_Incarnate]

i have yet to succed at like 90% of my plans, so here's hopin'