Best years for rebuild components.

Hey I cant really find what im looking for so hopefully i can pick the brains of you XJ gurus.

I may be rebuilding my 4.0 and want to make sure I do it with the best parts.

So question is.

Whats the best years and model for each of these. Keep in mind its most likely going to be a stock build, not the stroker. At least for now.

Block
Head
Crank

Im starting to get some killer valve train noise under hard acceleration so I may be doing just the head first, then the bottom end soon after. I have a 98 with 186k. If that head really isnt that bad ill just replace all of its components and port and polish it and slap it back on. Any input here would be greatly appreciated.

Jeremy

I dont know what would be involved but I hear the 87-90 Renix blocks are the best. IMO I think some body here said more nickle content or something. I dont know. Mine has 310000 on it , runs like a champ, and it has never been apart.

mcnamaag said:

I dont know what would be involved but I hear the 87-90 Renix blocks are the best. IMO I think some body here said more nickle content or something. I dont know. Mine has 310000 on it , runs like a champ, and it has never been apart.

Click to expand...

Seems like I've read somwhere that the '96-up had Noise Vibration Harhness webbing added to the block...I'm not positive so don't quote me on it. If they do have the added NVH I would go for that. I would rebuild the engine (new pistons, rings) if everything looks ok, and possibly look for a new HO head ('91 - '95).

*Disclaimer: I'm not positive the info I have supplied is correct, I've just recently been researching options for an engine rebuild, so take my info with a grain of salt.

Renix block, 91-95 head with 99+ intake on it. I'd double check, but I think the 99+ cam would also be considered one of the best stock. If you're doing a full rebuild anyways, I don't think the stroker is that much more to build.

Your head is OK. The 91-95 might be a bit better, but I don't think much. I'd P&P the one you have and maybe some high flow SS valves. You block is OK too. The 96 & up blocks have extra ribbing. It is suppose to add some strength and noise reduction. If I were going to build a stroker and bore it out, I'd use a RENIX block, probably the Mexican one. I'd get the 99.5+ (or 2000+) intake manifold. Slightly better flow and your serpentine belt setup should have much mods to make it work, if any. What I'd look at is the connecting rods. I think the latter ones are thinner than the earlier ones. Probably the best option would be Eagle or Scat connecting rods. The latter factory cams might have a better grind profile.
So I'd rebuild the block and head you have, use your crank too. P&P your head. Look at earlier connecting rods.
Tom

SO the 91-95 head is a bit better eh? If I were to P&P my 98 and put bigger valves in it would that make it better than a 91-95. I can source a 91-95 pretty dang easy and for only 50 dollars. Right now I really only want to do the head work and get to the bottom end when school permits. Granted if when pull off the head I find that the block is scored to death then ill find a way to do it all at once.

Is there any issues with just rebuilding the head without dealing with camshaft, lifters and pushrods?

jimmydaux said:

SO the 91-95 head is a bit better eh? If I were to P&P my 98 and put bigger valves in it would that make it better than a 91-95. I can source a 91-95 pretty dang easy and for only 50 dollars. Right now I really only want to do the head work and get to the bottom end when school permits. Granted if when pull off the head I find that the block is scored to death then ill find a way to do it all at once.

Is there any issues with just rebuilding the head without dealing with camshaft, lifters and pushrods?

Click to expand...

Look here for info:
http://www.jeep4.0performance.4mg.com/
Also, on porting the head. There are flow numbers for the different heads. I don't think there is much difference between the flow numbers for a 91-95 vs a 96-99. You can replace the head without taking out the lifters and camshaft. I put in bigger valves, Chevy SS 2.02 intake and 1.6 exhaust. If I did it again, I'd probably go 1.96 on the intake and 1.6 on the exhaust. Actually, its the exhaust valves that are more crowded in there. I also have adjustable roller rockers, so the Chevy valves work in that setup.
Tom