97grand4.0

All in with an oil change, could not find break in oil so STP with zddp added to Mobil 1 15k mile oil and a FL-1A filter, Not surprisingly on #5 cylinder which was filthy, the plug iis bad too so waiting on a set of new ones and standing down for the day. Napa sold me the wrong exhaust flange which I meticulously cut and re welded onto the pipe. Ugh.

97grand4.0

Ok so the big day was yesterday. It started and ran like a champ. The 'piston slap' type knock...completely gone and it runs like a different animal.
So on start up, the lifters chattered slightly for only about 10 seconds. Whew. Then I ran it in place for about 10 or 15 mins at a high idle. After a few minor issues I took it for little test drive up the road, and popped a front brake line at about 15mph. No biggie. Up and running again now.
One thing that did seem different right away was there seemed to be more heat shedding into the engine compartment, and I wonder if it has to do with better seating of the exhaust valves.

So in conclusion I am not sure whether the 'piston slap' type symptoms ..quiet at startup, then developing a knock which went away after warm up..were cured by the lifters or by the welding of the exhaust manifold, but, either way it runs great again. Actually I think it was in fact the lifters...they were all collapsed. Either way it's quite a relief not to hear it anymore.
I think if you pull a head and examine down the cylinder walls for scoring or heavy wear where the long part of the piston skirt is, if you have slap you know it right then from the damage on the wall. Mine had no scuffing or anything and were only slightly more shiny in that area so I had a good feeling from that point.

97grand4.0

UPDATE
So, I think problems may remain. There is a very light 'rattle' when I snap the throttle at idle. It remains, hot or cold. It was there before I started the head. Rattle on accel, rattle on decel. If it's rod bearings I might consider going in from the bottom end. But for now Ill drive it, its very light yet there. Diagnosing for sure will be tough, but, right now I'm getting a new roof put on so with 10 guys running around and the drive blocked it will have to wait.

I also think my O2 sensor left the building long ago. It shows it is crossing low and hi ok, but, the number of crosscounts looks poor. Also my fuel trims are still negative. Probably loaded with carbon just like the top end was.

dave1123

I'm telling you man, just try that Mr. Gasket "Cataclean." It sure made a difference with my 4.0. Used as instructed, it started working in 10 minutes! Even better than Seafoam because it cleaned out the converters.

97grand4.0

Really? I just cleaned the whole top end by hand, it's spotless. Converter only a couple years old...?

dave1123

You just said you thought they were carboned up. Whatever.

97grand4.0

Still having some driveability issues, but the more I iron the bugs out, the better it gets. Also think the lifters are still breaking in. At this point it's reliable and am zipping around town no problem. Strong, even and quiet. Still a bit of likely piston slap when cold but when warm it is very nice. Kind of wondering if the chatter might be something else like cam walk or the tensioner on the chain, or even something else.

dave1123

My WJ 4.0 doesn't have a chain tensioner. Just a plastic shoe that prevents the chain from slapping against the case. 240K miles and it had very little slack in it. Also, the cut of the oil pump gear puts a rearward pull on the cam so walk would be unusual. Overhead cams have that tendency.

97grand4.0

Correct. It's a shoe, now that I look again. When I did mine in May it was missing but I put the new one in. Odd, though, that the FSM is silent on this. No mention of it at all in the R&R of the chain.
Have read that flat tappet cams do not tend to walk, but, jeep did put that little spring and pin inside that hole in the preload bolt for a reason. Also there's a dimple on the cover.

dave1123

Yup, and GM decided not to and never had a problem. I guess it's a holdover from the 50's. Maybe even from the CJ 4 cylinder. Do you know why the really old jeeps had that weird thread on the oil pan plug? Because it was speced by the military to be the same as a spark plug thread so one could be used in the field if necessary. Can't have a jeep down because you lost the oil plug!

jgebauer

Good info

97grand4.0

Kind of chasing my tail on this now. The tap on cold start is still there, BUT ...not sure is piston slap still. What I did find is that my distributor seems to be where the sound comes from, maybe. I can turn the rotor a good 1/4". No wear on the dist gear, and the cam looks like the pattern on a rear end aka you can see the wear spot but it doesn't look out of the ordinary. However of concern is there are marks on the dist shaft where it goes into the oil pump, Like it's been pounding there. So not enough time to expore this fully but am considering driving out to my machinist buddy's place and talking to him about it. It runs rough too, when cold, stumbles,, maybe the new plugs got anti seize on them? not sure yet. Am also thinking that loose distributor gear cannot be good. I mean I know they have to have a LITTLE play so they can expand when hot, but, this thing is just clunk clunk. Not the bushing or bearing either, this is rotational play.

97grand4.0

Well the valve job seems to be maybe breaking in now, it runs nice. What happened was the IAC motor went south during the rebuild. Once I swapped that out, it starts and idles like it should, nice and strong. Before, it would hesitate stutter and die when coming to a stop or shifting P to R or R to D. No more now.
So..the distributor, only a couple years old a CH15. I welded the worn spots on the end of the shaft where it contacts the oil pump. Good there. Then I noticed end play was way out, like .050. from the factory. I ordered up some Moroso distributor shims for Chrysler distributors, which turned out to be not quite the right size, the ID was too small, so I backyard engineered them to fit with a rat tail file and drill bit. Anywho I got the endplay down to about less than .010 which is maybe a shad tight but I went for it anyway. Big difference, I wasn't expecting it, but accelerates much smoother and stronger. This is where distributorless ingnition..you can see the benefits. Just really nice. It's still a jeep mind you. Winds up real nice through 1st and 2nd, but like always Jeep dogs in 3rd and 4th but those are transmission problems, 200k on that. For now my work vehicle is doing ok and even kind of fun to drive.