i've been reading as much info as i can find on this head conversion for the last month(and there is a lot out there),but i'm very curious about the draw backs (if any).like with the intake having to be ground and then having to use oversize washers to secure it because the stock ones are not big enough to catch both the intake and exaust manifold.seems like a strong chance of having vacume leaks.also wondered about cooling issues on down the road.so if you can shed some light on these or any other problems with this set up please post up.

Mostly just posting up to get this back on the top of the pile.

I'm getting ready for this upgrade my self. I've not heard/seen/read anything negative about it ...... yet?

Also as a side note; My 15 year grandson is learning to drive, he parked his mothers Mercedes in the front room last Saturday.

I've done the conversion.
It's honestly the best thing you can do to the 4.2...as long as you compliment it with parts to take advantage of the free flowing head.

I used an XJ header, it fit perfectly...along with a Clifford intake. I did have to grind the stock power steering bracketry to fit the intake and exhaust...not a big deal.

Now this is where you can really take off with this upgrade. The headswap alone will net you power just because of the head design. You can do simple upgrades to this that will help out performance...a hotter ignition (TFI, HEI), free flowing exhaust, a better carb, fuel injection, the list is endless.

I went a more extreme route: High compression pistons, longer duration cam, 500cfm Edelbrock, TFI ignition, and desmogged. This thing made a huge amount of power and torque...way more then a stock 4.0. The downside to my build was the carb. It made great power as long as the jeep stayed on flat ground:laughing::shaking:

The upgrade created a hotter running motor in my situation. I expected it having read as much as I had and doing the extra modifications. I louvered my hood which made a difference, but it still ran warmer then the 4.2 did. Go with a 3 core radiater maybe, with some water wetter perhaps.

well i couldn't have got laid off at a shittier time(while in the middle of a rebuild).i had decided to pass on the 4.0 head conversion and do as clifford performance suggest and deck the block,shave the head .60,and change the cam,lifters,and push rods.now due to finances im not to sure.but ive already got the three core radiator and did the GM TBI (best mod yet).so time will tell,but i would like some input on cam selection sutch as crower,clifford,or what?

I've gone with Comp Cams on my last 2 builds and haven't had any issues. Good tech support also. Run your build information by them, tell them what you want out of the engine, and they can hook you up.