xj cylender head on a yj?

muddober3

Member
Joined
Jun 9, 2013
Location
NORTH WILKESBORO
Hello all, been awhile sense ive been on here. I just bought a 93 yj today that is overheating, the previous owner has put t stat, waterpump, radiator, flushed the system, and it still over heats very quickly. I got it home and started it up , and from a cold start to pegging the needle , was just a few minutes. Im thinking head or gasket. I have a rebuilt 1990 xj head that I can put on if its compatible, but im not sure. if anyone knows if it will work or not, id appreciate some help here. thanks.
 
1990 XJ is the older Renix motor, the 91 and up XJ or YJ are the Chrysler MPI 4.0L HO. The Renix head will bolt up to the block, but the exhaust ports are different, something like over 1/4" mismatch IIRC. Some people say the mismatch is no big deal. I don't like going thru all that work, knowing I'm 'losing' something right there at the head.
 
it will work fine, ive got several heads laying around if you need one. I'm in Boone not too far so call if you still need one. i'll even trade flat out for yours. heres a little jeep head/block facts to consider: the original AMC 87-88 Renix heads are the thickest and best heads that came on the 4.0. sure they might not flow as good as the HO but with little porting/gasket matching you'll get way better results and longer lasting toughness out of them and never really worry about cracking one. I love those heads because of this. 90 to 97 are pretty good but weigh less and 99-06 are junk and crack in a heartbeat. so choose wisely in your options. the flow rate as people refer to is really not that great a increase from renix to HO, not enough by itself to notice increase, I would know cause I've done interchanged all different heads and intakes and well, never really thought was worth the swapping. I was MUCH happier with porting/Gasket matching and polishing the renix original head and that was a major increase and could beat a 99cherokee sport HO all day long so......I love a jeep. good luck 828-217-0730 John
 
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