So im in a diesel tech school and one of the classes is rebuilding heads. well since i dont have a diesel and a gas head is virtually the same as a diesel head in components, im allowed to bring in a gas head to rebuild. im wondering if a later model 4.0 head will fit on my 92 xj with NO mods. bolts right on. will it? and is there any perks to trying to put a newer model head on my 4.0 or should i just find a head off a 92 xj?

 

Some say the 7120 head('91-95) is the best head put on the 4.0. To answer your original question, any 4.0 head will bolt on.

 

if i put a new model head on there i would have to get the newer intake and exhaust manifold right?

 

2000+ heads will require a new exhaust IIRC. 96-99 will be bolt on,with the exception of the temp sensor on the back of the head, some/most 96s have the hole for it, but you can get a new tstat housing with two ports for the sensor, you will have to extend the wires.

 

Agree, best flow, prior to stricter emissions Laws

 

on the 7120 heads, are they prone to cracks or anything else i should be looking out for when i go to a jy to pick one up?

 

Not any more so than any other head, definitely not like the 0331.

 

So i bought a 4.0 head today. its only got 160K on the motor but the jeep was rolled. its a NON HO head. Will it still work?? i guess i should have figured this out before i bought it

 

what are the differences in a HO and a non HO motor?

 

Int/Exh ports, you will need to use the manifolds from the renix(non HO) vehicle. I know it was only 8hp difference between the renix/ HO engines, but with the tunes of the engines I dont know if it will be worse,better. If it were me I would try to sell it and find a HO head. Maybe you could PM, Cruiser54 , he knows a lot about the renix engines.

 

i blew up a 94ho and swapped in a 88 4.0 block and head and used the intake manifold off the 94 not that this completly helps but i do know u can basically do the opposite of what your trying