thedave360 Posted March 6, 2011 Share Posted March 6, 2011 Well, its tax refund season and I've managed to convince the wife to let me use some of the funds to rebuild my 4.0 HO in my Comanche. I have a few questions and am looking for advice from people who've done this before. I plan doing everything possible- main cam and rod bearings, oil pump, all the gaskets, refurbished injectors, rings, turn the crank, hone the cylinders. maybe new pistons and rods? Any advice or words of wisdom for getting the engine out of and back in the truck? Any things I should do or should not do? Any good places to get a complete rebuild kit? Is there anything that you wish you would have done while you had the engine out. Link to comment Share on other sites More sharing options...
Pete M Posted March 6, 2011 Share Posted March 6, 2011 what's wrong with the current engine? Link to comment Share on other sites More sharing options...
thedave360 Posted March 6, 2011 Author Share Posted March 6, 2011 it has about 200000 miles and it has crappy oil pressure. I'm running 2qts Lucas and 4qts 40w, and i'm getting less than 20psi at highway speed. I want to rebuild it before it throws a rod or something and cause more damage that i'd have to fix. Link to comment Share on other sites More sharing options...
Pete M Posted March 6, 2011 Share Posted March 6, 2011 you're not using a fram filter are ya. :D checked against a direct oil pressure reader? What's your compression like? Link to comment Share on other sites More sharing options...
thedave360 Posted March 6, 2011 Author Share Posted March 6, 2011 No sir, I only use Mobil1 oil filters. I connected a manual gage to it and it reads the same as the electric one in the dash. I haven't checked the compression...but I imagine it isn't good. I drove an identical truck to mine in much better shape with less than half the miles and I could not believe the difference! Link to comment Share on other sites More sharing options...
91coMANche Posted March 6, 2011 Share Posted March 6, 2011 I was in your shoes but instead bought a ZJ 4.0. They live easy lives behind an automatic and you can get them for $300-$500 with around 100K on them. The 96-99 engines swap in and have everything upgraded including block/piston/rings. I would just grab a modern 4.0 and enjoy the power. Also the modern 4.0 has a block casting that reduces lots of noise. Link to comment Share on other sites More sharing options...
Pete M Posted March 6, 2011 Share Posted March 6, 2011 x2 on the junkyard engine. you've got an HO so a late model block is even easier for you than us renix guys. :thumbsup: also, perceived power differences could be anything from a failing fuel pump or sensor, to a clogging cat, to different tire sizes. just about anything can make/break max hp. Link to comment Share on other sites More sharing options...
87Warrior Posted March 6, 2011 Share Posted March 6, 2011 Kind of in the same boat: viewtopic.php?f=2&t=28857 At very least, you might want to research cams. When I simply rebuilt my Rubi's 4.0, I was disappointed I did not try to squeeze more power out of it. Link to comment Share on other sites More sharing options...
91coMANche Posted March 6, 2011 Share Posted March 6, 2011 I've known a few people with failed cams once they upgraded. It could have been a bad manufacturers batch, the details of which I am unsure. Generally speaking, the 4.0 in factory displacement and build is an ideal engine. Link to comment Share on other sites More sharing options...
87Warrior Posted March 6, 2011 Share Posted March 6, 2011 If you are only interested in a basic rebuild, visit your local machine shop and see what kind of shape your block is in. Once you know what is needing replaced, visit your local Jeep parts department for all parts, gaskets and seals. They can provide you with over sized pistons if need. Have the shop assemble the short block and balance. This is how I rebuilt my TJ 4.0 and have put 90K miles on it with out a problem. Link to comment Share on other sites More sharing options...
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