My head gasket is leaking oil on the passenger side so I’m going to replace it. I already resealed most of the engine and was considering having the head rebuilt while it’s off. A local shop quoted me at $360 for a complete rebuild (magnaflux, resurface, valve job, valve seals) and a 3-4 day turnaround. The engine just passed 200,000 miles and I’m trying to make it last. Would most 4.0 heads be due for a rebuild at this mileage? I’ve seen newer higher compression engines need valve jobs at lower mileages, just not sure about this old iron beast.

you say you want to "make it last", the price seems reasonable, and it should perform a little better, so I think you know the answer

What year is your rig?
I think 99 was the last year ot TUPY head. If you have a TUPY head, it's worth a rebuild.
2000 or 2001 had the failure prone 0331 head.

1996

It is extremely unlikely that your head gasket is leaking oil, simply because no pressurized oil flows through the head gasket, It flows through the pushrods.

Oil seeping between the head and block above the distributor?

It's been my understanding that TUPY was the designation of the 0331 heads that were not failure prone.

No XJ had a tupy head factory. The TUPY head was on later 02+ jeeps to fix the cracking issue with the 0331 heads which were on XJ's for 00-01 only. If anyone has an XJ with a TUPY head then it means its been swapped.

I am a new XJ owner and from the "internet research" I've done over the past week, it is my understanding that 0331 heads marked "TUPY" did not originate until 2002 to 2006 (final production year?). They are allegedly stronger with a beefed-up casting to mitigate the cracking issues. The 4.0 inline-six was last offered in Jeeps in 2006. I have no idea if they continued production after that. Sometimes the manufacturers will continue to make the engines long after they kill the line from their motor vehicle lineup.

But, since you have a 1996 (non-ignition coil) then I think the heads from pre-2000 and post-2001 will all be fine. The 2000 and 2001's were the crappy ones (or at least sensitive to overheating). Considering the mileage on the motor, I would just install a used serviceable head and move on. If you can find a machine shop that can check the head and you're willing to pay the $150-400 for their efforts, then more power to you.

I have a 2000 XJ and I am going to buy a junkyard TUPY head from a 2003 GC for $150 and have it gone thru by my local machine shop to IRAN (Inspect and Repair As Needed). It will still be cheaper than me buying a $700 brand new Chinese cast head that has been professionally inspected by a US shop (Clearwater).

What is that indicative of? I'm not trying to hijack but... I had massive oil leakage on the passenger side of the motor originating from the head (and a tiny bit of oil in the coolant). No observed coolant in the oil...

I believe it's head gasket. Very common.

Yep. I replaced the rear main, oil pan gasket, oil filter adapter, and valve cover gaskets then degreased the engine. This one is slow but it’s leaking, and summer engine temps are a bit higher than I’d like even after replacing the entire cooling system, so I figured I’d replace the head gasket.

It’s leaking man. I fixed all the other leaks and degreased the engine twice. Both times the oil was dripping down from the head gasket on the passenger side. Above the head gasket is dry.

I actually have a spare 4.0 in the shed, I was thinking of having the head rebuilt and swapping the heads when I replace the gasket in the Jeep. Any thoughts?

as long as it fits your 4.0, why not?