Kevin Holbrook

Hello all,

Just bought a 1999 XJ from my aunt. Only 80,000 miles, vehicle is in great shape!

Before she sold it to me, it had an overheating issue and the head is cracked. Oil in the coolant, disappearing coolant, etc.

I spoke to Clearwater Cylinder Heads about a reman 630 head, which they offer, but they recommended I get the new casting 331 head instead. I have been reading about differences in temperature sensor location, exhaust port size, etc, and the differences concern me.

There has been a lot written about putting a 630 head on an engine that originally had the 0331 head, but I haven't found anything about switching in the other direction.

Any recommendations regarding going with a reman 630 vs a "new casting" 331?

Thanks in advance!

5-Speed

I believe you would have to change the intake manifold and header by going with the 0331 head. Something is different but I cant 100% remember what. It might have only been the exhaust....

tjwalker

How was it determined that the cylinder head is actually cracked? The symptoms you mentioned can also be seen with a blown head gasket. Yes, any cylinder head can crack but the 0630 is pretty hardy. There is a chance that it is the head gasket, not the head itself.

I would start with a compression test on all cylinders. Two adjacent cylinders reading low could just be the gasket. Pull the head and perform an inspection. A machine shop would be able to test your head and tell you if it is actually cracked or not.

bluejeep2001

Would never put a 0330 head on anything if i could avoid it...even if it belonged there. The 0330 head will not bolt up to an 0630 exh manifold without an adapter plate and the ports are really small. The 0330 has mounting holes for the coil rail. There may be a hole for the temp sensor to gauge depending on the date the head (0630 ) was built... I even think the valve covers are the same, where the 0720 needs a different valve cover..no other differences..The 0620 is a durable head, not prone to cracking but it can be done. If its coming off, a machine shop can tell you fairly quickly

Kevin Holbrook

OP here...

Thanks for the info.

If a new/reman head has to be used, will definitely go with a 630. I don't know why Clearwater is trying to sell me their New head which is based on the 330 head.

I do not know that the head is cracked, but do know that the engine overheated quite a bit. The electric fan had been replaced with an aftermarket one, and there was an electrical adapter plug which could be plugged in either way. Well, it was plugged in backwards, so the fan ran backwards. This wasn't an issue when driving, buy my aunt spent a lot of time idling in parking lots and drive throughs and she told me it overheated a lot. It just worries me that all of this may have led to a cracked head.

I drive the Jeep every day, and would like to have all of the parts on hand when I take it down, that's why I wanted to have a new head when I started the job. I should probably just make arrangements for the vehicle to be down for a while to truly check the status of the current head.

sstout

I agree with what someone mentioned above. Take the head to a machine shop and have them magnaflux it to check for cracks. I just bought a clearwater 0331 head a few months ago. While really nice, they are not cheap. Having the old head checked for cracks could save you some cash as well

Irishdeath88

I just had my 1998 xj head gasket blow. I am curious, if the head isn't cracked, should I replace any of the parts on the cylinder head or just leave it alone?

bluejeep2001

The 0630 head is fairly robust...if you blew the head gasket, how hot did it get? You might want a machine shop to check for flatness or warping...if none-replace the gasket

Irishdeath88

it didnt get over 210 according to my temp gauge but when I pulled over, due to the shuttering and temp gauge racing up quickly, there was coolant pouring out, I haven't gotten full eyes on exactly where from but just looking under my jeep when this happened it was running down the back of the motor.

fb97xj1

Running down the back of the motor could be a rusted out freeze plug on the back of the head. Check the ones on the side of the block, too. There is also a freeze plug on the back of the block, but the transmission has to come out for that one.

Irishdeath88

From what I can see all my visible freeze plugs have been replaced. I am a little worried that who ever owned the jeep before me didnt replace the ones behind the bell housing. Any words of wisdom from anyone before diving into that job?

Billyray59

Hello ,and hopefully I can jump in here and ask a question .I have an 0630 head and it is cracked on the milled surface between cylinders 3/4 between the metal head gasket rings ,will it leak if I put it back on ?

Billyray59

Hello ,and hopefully I can jump in here and ask a question .I have an 0630 head and it is cracked on the milled surface between cylinders 3/4 between the metal head gasket rings ,will it leak if I put it back on ?

Sig220

I have always been told it will. As it gets hot the metal expands which means the crack will widen. I just had the experience of bringing a head to a machine shop and being told after testing that it was cracked. Not what you want to hear but it happens.
Of course, my engine was seriously abused with a hole in one piston (probably caused by water exploding under pressure) and a partially melted piston. I elected to replace head and block.

bluejeep2001

Do a search on ebay for jeep cyl heads...you can find dozens of reman for 2 or 3 hundred. DO NOT PUT A 0331 on anything you own