4.0 Head reassembly

Hello,
I'm helping a friend swap heads on a 2000 XJ 4.0L. Last weekend I successfully pulled the cracked 0331 head (out with manifolds attached).

Tomorrow I am cleaning all mating surfaces and installing the new gaskets and head. My question relates to lubrication of the cylinder bores, lifters, etc during reassembly. I am paranoid that the engine has sat all week with the head off (I covered the block). Is it possible for the piston rings to lose their "seal" and thus compression on restart?

Can I blow out and clean the cylinder bores and tops of the pistons with carb cleaner followed by brake clean? I've heard of coating the tops of the pistons with 2 cycle engine oil to capture the grit during clean-up of the old gasket material. Is this a good idea? Does it really matter?

I plan to use engine assembly lube as directed by the FSM on the rockers and push rods. Can I also dab some on the cylinder bores? I have also read this can lead to spark plug fouling.

Was it a mistake to let the engine sit for a week between break-down and reassembly?

Thanks folks

I'd wipe down and/or spray some SAE30 oil on the cylinder walls, re-assemble, crank over with the plugs out a few times, then fire it up. That's what I've done on a SBC 350 head gasket job. YMMV.

Yeah you can wipe them down just oil the cylinder walls and everything else you're putting back together. I've used engine oil in the past when reassembling already worn parts. I'd strongly encourage you to change the oil at least twice at no more than 200-500 miles after the repair. There is likely water and grit in the oil from the repair. If you cut the filters open you'll probably see the griit. Mechanics often change it the first time it comes up to temperature, before it ever leaves the shop

duke000088 said:

Tomorrow I am cleaning all mating surfaces and installing the new gaskets and head. My question relates to lubrication of the cylinder bores, lifters, etc during reassembly. I am paranoid that the engine has sat all week with the head off (I covered the block). Is it possible for the piston rings to lose their "seal" and thus compression on restart?

Can I blow out and clean the cylinder bores and tops of the pistons with carb cleaner followed by brake clean? I've heard of coating the tops of the pistons with 2 cycle engine oil to capture the grit during clean-up of the old gasket material. Is this a good idea? Does it really matter?

I plan to use engine assembly lube as directed by the FSM on the rockers and push rods. Can I also dab some on the cylinder bores? I have also read this can lead to spark plug fouling.

Was it a mistake to let the engine sit for a week between break-down and reassembly?

Thanks folks

Click to expand...

Your rings will not lose their seal in a week's time. All you really have to be concerned about is having clean, lubricated cylinder walls at start up.

If I have to go there, I stuff the holes with clean, oil-soaked rags before scraping and cleaning the deck. That will capture any trash that may fall in the hole.

If it is too late to stuff the holes, clean them out with a shop vac.

DO NOT USE SOLVENT TO CLEAN THE CYLINDERS!

When you are ready to reassemble, use one of those clean, oil-soaked rags to put some lubrication back on the upper cylinder walls. If your rings look dry, a few drops of oil where they meet the cylinder wall is adequate.

Good luck!

Thanks guys. I like it.

Here's my latest dilemma: I didn't do my homework and I used some Scotch Brite to get some stubborn bits of head gasket off the block. I know. It's terrible. But what is the best move I can make now to improve my odds of engine survival?

Multiple oil changes right after I start it up?

Hypoid's comments are also what I've done I just didn't think to write it. A Scotch Brite Bristle Disc is unlikely to kill your engine anytime soon. It's not like you used it to remove the entire gasket. Vacuum up and use the oily rag method. I usually use brake cleaner on the block deck until the towels come off clean. I also clean out the head bolt threads with brake clean followed by a thread chaser. Do not put any sealant or coating on the head gasket. Remember it's a 3-4 stage set/check torque on the head bolts and the front drivers side gets some thread sealant and less torque.

duke000088 said:

I plan to use engine assembly lube as directed by the FSM on the rockers and push rods. Can I also dab some on the cylinder bores? I have also read this can lead to spark plug fouling.

Click to expand...

Use motor oil... it'll safely burn away, and will flow much better... assembly lube is too thick for this....