Cherojakee

In the middle of a partial engine rebuild, replacing pistons, lifters, and gaskets.

Jeep has 107k miles on it. Developed piston slap a few thousand miles ago. Narrowed it down to cylinder 5 by pulling the injectors one at a time.

Right now I have all the pistons pulled and cylinder bores measured. All about .001-.002 oversized which I would consider normal wear for 100k engine. So I'm just going to replace pistons, Lifters, gaskets, and maybe a couple other things while I have it apart.

The offending piston did have a crack in it. So new piston should fix the slap. Started this thread for suggestions or if someone is doing the same repair and has any questions I might be able to help with. This forum has helped me with a lot of repairs and general info and I'd like to give something back.

5-Speed

If it was my engine, I would just have it bored to the next size up. .001-.002" is a lot when you are talking piston to wall clearance. Say your engine originally had .003" piston to wall clearance. Adding .002" will take you to .005" piston to wall clearance. That is very excessive for a cast piston. You will most likely still get piston slap. Even if you put forged pistons in (which expand more then a cast piston and require a larger piston to wall clearance), I would still say thats too much of a gap.

BTW - How are you measuring the bore size? Digital caliper? An actual bore gauge?

Cherojakee

Well like I said in the op, I only had piston slap in one cylinder and that was because a cracked skirt. Every engine with a decent amount of miles is going to have some wear. On the bore and the piston. If you think everyone is driving around with perfect 3.875 bores, your probably mistaken. I'm rebuilding on a budget or else I probably would pull the block and have it bored. I feel comfortable with the tolerances, plus the new pistons will be tighter because their new with no wear.

I used a t-guage and micrometer. It is a little more tedious than a bore gauge, but very accurate if you know how to use them. And I have a lot of experience with measuring instruments.

cruiser54

Replace the piston and keep on trucking.

andrewmp6

If im replacing one or all 6 id think hard about a stroker kit for it.Your already there why not up the power while your at it.

Cherojakee

I'm doing a budget rebuild. Well that was the plan anyway, the machine shop called today and told me the head is cracked. The dreaded 0331.

andrewmp6

a clearwater head isnt that badly priced

dzywicki

I did the same thing a couple of years ago due to a cracked piston skirt. I replaced pistons/rings, connecting rod bearings and oil pump. Only problem I had was getting air in the power steering lines. Caused some horrible screeching after a few minutes of running. Oil pressure is 60 cold and 35 at hot idle. Been running great for ~15k miles after the rebuild.

investinwaffles

and upgraded to prevent cracking in the future.

Or get a junkyard head and have them magnaflux it and maybe clean it up

97grand4.0

Cracked head. Did you find a hard failure of the piston on #5?

Rogue4x4

He already stated he had a cracked head. And that the skirt was cracked on 5.

s346k

i would suggest a finish bore at the very least. especially if you are putting new rings in it. something to rough up the wall so the rings will properly seat. maybe take a honing ball to it. something.

edit: inspect everything very carefully. it's very rare to have a failure in the cyl and only 1 part be hurt.

97grand4.0

Verify the measurements as stated. If ok, the standard would be to use a ridge reamer and a glaze breaker and call it a day.

5-Speed

Do you happen to have a picture of the crack in the piston and the #5 cylinder? Curious to see where it cracked on the skirt.

Cherojakee

Yea think that's what I'm gona do. Seems like the Clearwater heads get good reviews on here.

I think the chances of finding a tupy head around where I'm at are slim. I've had other parts I've looked for at junkyards and it's usually a goose chase.