Need advice on 4.0 rebuild

[JeepsAreBuilt]

Ok, I got a 89 4.0 Renix motor I pulled out of my XJ and it was knocking pretty good which is why I decided to pull it out. I planed on doing a stroker build - but now am thinking of doing a stock rebuild or overhaul for now while I gather stroker parts as I want to do a GOOD build. So, I tore my motor apart and could not visually find the cause of my "rod knock" noise. So I started measuring parts and cant not determine if its whats causing my knocking noise. Heres what I've found so far.

Crankshaft journals measurement specs - mains 4 were .0008-.0009 under specs. Rod journals all were in specs.
Piston to wall clearance was .005 average on all cylinders. Out of taper .001 on 4 cylinders, and 2 were almost .002
The bores look good, with very little ridge. The motor has 235K miles on it.
Camshaft bearings and journals visually look GREAT.
Bearings on mains and rods look fine and show wear.
One piston has small scorning on the side - as it looked like it was starting to seize up, but the bore looks good.

What I want to do is just do a re-ring kit and put it back in the Jeep. I want to run a ridged hone down the cylinders and clean it up and it probably will fix the ridge. Since there is one piston that isnt in good shape, I thought I'd buy a new set of standard pistons. Speedpro for about $20 each. Also get the crankshaft polished and get some .001 oversize main bearings - Are these are available somewhere ?

So my question is my piston to bore clearance too excessive ? Will new pistons reduce this spec ? Will honing the bore remove too much material ?

Thanks for any input.

[IH 392]

You didn't say what your rod bearing clearance is? but the .005" piston clearance is a CRAP! load, should be .0015"-.002, it's likely piston slap your hearing.

[JeepsAreBuilt]

I did not get the rod bearing clearance measured before I returned the measuring tools I borrowed. I still could get it measured if i really need to.

I understand that the FSM says the piston to wall clearance needs to be .0009-.0017 and that mine is way out of specs which I am having a hard time to believe, the motor did run great. One cold morning the motor just started to knock loudly.. and I drove it like that for a week without any problems. I pulled the spark plug wires one by one and found that pulling #2 quieted down the motor the most. Do you think my pistons has worn out or bore or both ?

[4.whoa]

If you're gonna get pistons anyway, just go with .020 over( don't know availability of .010+). Yeah you'll have to bore it ,but it'll be right. The piston scoring is usually from the piston twisting a bit. good chance thats what you heard. I just stripped one down like that .001 -.003 taper on several bores. It was loud

[JeepsAreBuilt]

Ok thanks for the input.

I am now thinking I'll hone it out .010 and get new pistons and rebuild. What do you guys think about the stock cam and bearings.. 235k or so miles on them. They visually look good. Should I measure them ?

[IH 392]

.010" over pistons aren't available, you'll need to go .020" at least.

[4.whoa]

Definitely get new bearings. When boring/honing you need to get all the "trash" out so the cam brgs should go too. Stock cam SHOULD be ok, did you keep lifters in order ? If not get new ones DONT put old lifters on different lobes maybe check your oil pump & timing chain as well. Can keep em when doing stroker and it'll keep what you do now in good shape

[JeepsAreBuilt]

.010" over pistons aren't available, you'll need to go .020" at least.

Found these 3.885"(0.010 over) at summitracing: http://www.summitracing.com/search/Depa ... s=Rank|Asc

Looks like a set a set for $156.. and a coated skirt set for $216 - whats the point of coated skirts and are they worth it ? Also these dont say the dish cc ?? How can I figure my comp ratio with these ?

4.whoa - I'll be honing it with a rigid hone, no boring. So.. I wont be hot tanking the block. Do you still think I'll need new bearings ? For the lifters.. I want to get new ones. One of them sounded like it wasn't pumping up all the way when I had it running.

[IH 392]

If that's correct those are the first .010" over pistons I've ever seen for any automotive engine?

If your engine has 235,000 miles and "very little ridge" in the cylinders I'd be measuring those pistons really close! to make sure they aren't .030'', .040" or even .060" over already, the AMC/Jeep sixes wear the thrust side of the cylinder rather excessively.

[JeepsAreBuilt]

If that's correct those are the first .010" over pistons I've ever seen for any automotive engine?

If your engine has 235,000 miles and "very little ridge" in the cylinders I'd be measuring those pistons really close! to make sure they aren't .030'', .040" or even .060" over already, the AMC/Jeep sixes wear the thrust side of the cylinder rather excessively.

Must be a error by summitracing for listing those .010" over pistons then. I looked for rings for them, and could not find them anywhere. Also seems like nobody else sells these .010" oversized pistons. I looked at my cylinder walls again today.. and i do see more ridge on one side - must be that thrust you are talking about. It is on the passengers side of the motor. I must have assumed the ridge would be the same all around, which its not, so theres more ridge on the thrust side. So.. my plan of .010 will not work. I'll have to go at least .020"