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head question

pballbeanology81

NAXJA Forum User
Location
roxboro nc
I have a 87 cherokee with the 4.0. I cant find any engine performance parts for it. my question is what is different from the heads on my engine and the heads on a slightly newer xj 4.0? i want to do a header and add an intake manifold! please help!!!!!
 
It already has an intake manifold, you can't add another one!



On a more serious note, I believe some people have upgraded to just newer model HO intake manifolds, but the gains are questionable. Most will tell you the header isn't worth your time.
 
The heads on a 91-96 have the casting number of 7120. They are by far the best flowing heads to get. It will give you big increases in HP/Torque. When swapping to the newer head you have to replace EVERYTHING from the head up. TV cable, intake manifold, exhaust manifold, throttle cable.. everything!
The only thing that you wont be swapping is sensors. Re-use your RENIX sensors. The TPS needs modifications, or an adapter to mate up to the HO throttle body, but other then that its basically just swapping everything out and over. This scenario is the only way to find aftermarket bolt on upgrades.

They do make a exhaust manifold "header" for the RENIX (which you have) buts its a huge waste of money unless you have had head work done. Even then, its still a pretty big waste since the head is the most restrictive of them all.
 
on my stroker I re-used my '89 renix head. I had the intake and exaust polished, the intake gasket matched porting, the exaust runner ceiling got minor grinding (the exaust is kinda thin), enlarged to 2.02int/1.60ext Manley race-flo valves, and topped it off with harland sharpe 1.6 roller rockers (machined in studs ofcourse). I cleaned up all of the oil passages also.
I dont know how much increased from stock, but doing that will give gains. The porting shouldn't cost you more than $300. I spent about $1000 when it was all said and done.
Considering that price against upgrading to a newer head (with having to get all new parts to match up to an HO system) the price seemed not too bad.
 
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