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Discussion Starter · #1 ·
I have an '89 YJ that came with the 4.2. The PO (no clue why) swapped in a 4.2 from a 79 CJ 7. He reused everything other than the block and head... So the intake and exhaust manifolds are from the original '89 4.2.

I have issues with the exhaust and intake manifolds leaking. So my question is, was there any difference between the intake and exhaust manifolds for the 79 CJ 7 4.2 and the YJ 4.2 that would cause them not to seal up. I am using an exhaust/intake manifold gasket for a 79...

Someone please help, this is driving me nuts...
 

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Nope, they are the same engine. I have an 87 4.2 and have the same curse.

Mine goes thru exhaust gaskets at a rate of 1 per month. Just a very poor design on the way it mounts. The last time i had it apart, i used a surface grinder to smooth down the mating surface of the exhaust manifold and used a fel-pro gasket that has the metal inserts in it.

I was told by the local speed shop, that if you get some old school header gaskets (the ones made of asbestos) and soak them in water over night, then install them, when they dry, they mate to the surfaces and give you a good seal. This is my next step other than going to a full tubed header, but the mounting studs are the same on it as well.
 

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the 81 and up takes different manifolds than the earlier motor.
 

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Discussion Starter · #4 ·
the 81 and up takes different manifolds than the earlier motor.

I just got done replacing the head gasket. Installed the exhaust and intake, it leaked (i overtorqued the bolts, :banghead:). Took everything off and put on a new intake and exhaust gasket, torqued them correctly and in the proper sequence. Does not seem to leak. It is a '79 4.2 head, but the intake and exhaust manifolds are from an '89 4.2. Any idea what that difference was starting in 81? Cause it seems to be working at the moment...
 

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the aftermarket manifold makers like clifford and offenhauser make 2 manifolds, the change was in 81. not sure exactly what changed.
 
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