I have an 87 cherokee. put a 94 4.0 in. I had a brand new 2686 head. It appeared the same as the head off the 94 even though the casting was 7120. I over heat now though. Is it functional to have a 2686 head replacing a 7120 head? I have a new radiator, water pump, t stat and reservior and everything for my cooling system... thinking the head is the issue...?

 

Itll IIRC thats the Renix head, so youll some power loss due to the port sizing.

 

would the renix not be functional though and cause overheating?

reason I wonder... we started on the 87 4.0 thinking cooling system... ended up having cracked head... replaced the head.. still had issues. found the block also was damaged so we were still boiling over.

got a 4.0 from a 94 cherokee and tossed that in. still ran into boil over issues with cooling system. tstat, water pump were new... had radiator serviced prior to this engine swap. had no heat to heater and kept boiling over... you could touch parts of the radiator and tell it wasn't flowing through the full radiator. got a new all metal upgraded radiator after reading the reviews on the original ones failing... i can drive around the block and then the by the time I idle in the driveway it is boiling over again. Burped the system to clear air and got heat back to the heater but then half way around the neighborhood again heat is gone and boil over happens again.

Officially at a loss and tired of the year it has taken saving money for parts and the labor I have put into trying to get this jeep running... only thing I could think of would be that what I was told about the 87 head being compatible with the 90s block is incorrect.