I have a 98 XJR with 78000 miles that apparently needs new head gaskets. Blowing white smoke out the exhaust and compression low on the drivers side bank. (PS bank 130, 115, 120, 115 and DS bank 90, 85, 30 and final cylinder havent checked yet ). My question is as big of a job as this is, my car has the original engine which is Nikasil. Is there any reason to choose the newer aj27 block over rebuilding my original one? Except it would be a lot cheaper to rebuild my engine since I will be doing the work myself?

 

Very good reasons to not use the AJ27. See the post fro a few days ago and other archives for the differences.
Pass the popcorn, bob!

 

If the cylinders are in good condition yet why not just replace the head gaskets after checking that the heads are not warped. There is a good chance the liners are damaged, but still worth a look.

Whether you rebuild this engine or replace it, it's a good idea to use the mls head gaskets for the 4.2L engine to limit the chance of a repeat.

 

I will probably start the tear down next Monday. That will give me a good idea of the cylinder wall condition, and I will decide from there with the input of this forum of course.

 

If you had no nikasil issues as of yet you will most likely not. I also have to say that my nikasil block made a nice impression on me when I disassembled my motor. Cast iron/steel cylinders wear way more than nikasil as it's much harder. If you're gonna use the gasket kit we spoke about, it comes with valve seals. I'd do those if I were you as the rubber on them will be hard and brittle after so many years. Amazon has a good valve spring compressor I used for under $50 http://www.amazon.com/gp/offer-listi...&condition=new

 

It seems the nikasil was a good technology .. it just happened
to be ahead of the fuel quality being delivered at the time.

 

Don't overheat the engine. Severe overtemp can damage the linings as well.

bob gauff

 

Thanks everyone for the responses. Adam699 thanks for the link.