Rebuilding my zj engine - really no idea what I'm doing. Pics inside, advice needed. - JeepForum.com
 
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post #1 of 5 Old 11-16-2019, 10:03 PM Thread Starter
daringescape
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1993 ZJ 
 
Join Date: Apr 2011
Location: West Covina
Posts: 9
Rebuilding my zj engine - really no idea what I'm doing. Pics inside, advice needed.

I have the head pulled and pistons removed, but I don't know what I'm looking for here. Based on the photos linked, should I replace the pistons or just the rings? Also, do these valves look shot? Anything else you guys see that might need to be done?

I will also of course mic and hone the cylinders, replace all the seals, rod bearings. Do I need to do the cam bearings?

I am planning on getting a rebuild kit - but there are quite a few out there with various components (pistons, camshaft, etc.) - I'm not sure what all I should replace.

https://imgur.com/a/v0PdvG4#v2KetrL

Thanks!

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post #2 of 5 Old 11-17-2019, 10:16 AM
V8GCZJ
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Need better pics of the piston skirts and bores where they rub. This is where you will see scorning/scratch lines. If they are to deep you will need a bore and new pistons. No pics of the mains either. The rod bearing surface on the crank looks a little worn. May need to be ground down. If you know anyone with engine building experience have them examine it. Hard to give advice going from the pics (or lack of).
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post #3 of 5 Old 11-18-2019, 09:11 AM
zjosh93
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Everything in those pictures looks fine. Why are you rebuilding? Did you check compression or do a leak down test before tearing it apart?

Bores look okay but it would be nice if they weren't covered in dirt in the pics. The right way to check them is a bore gauge or snap gauge and micrometer. Typically they wear most at the top of the bore where the piston rocks. I don't see any step worn in the top of the bore so I'd guess they were in good condition.

Pistons look fine. You'd need to mic them but the wear looks minimal.

Valves are dirty but nothing out of the ordinary. No obvious damage. You'd need to pull them to check the seats.

I hope you kept track of which rod caps go to which rod and what direction they were installed... They are machined as matching sets.

Crank looks used but I don't see anything bad there. Any scratches big enough to catch your fingernail and it should get machined.

There are specs for everything in the motor. You just need to find them and check. A good set of micrometers and a set of snap gauges can tell you almost everything you need to know.

Most of rebuilding a motor is cleaning parts and keeping them clean.
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post #4 of 5 Old 11-18-2019, 10:11 AM Thread Starter
daringescape
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1993 ZJ 
 
Join Date: Apr 2011
Location: West Covina
Posts: 9
Quote:
Originally Posted by zjosh93 View Post
Everything in those pictures looks fine. Why are you rebuilding? Did you check compression or do a leak down test before tearing it apart?

Bores look okay but it would be nice if they weren't covered in dirt in the pics. The right way to check them is a bore gauge or snap gauge and micrometer. Typically they wear most at the top of the bore where the piston rocks. I don't see any step worn in the top of the bore so I'd guess they were in good condition.

Pistons look fine. You'd need to mic them but the wear looks minimal.

Valves are dirty but nothing out of the ordinary. No obvious damage. You'd need to pull them to check the seats.

I hope you kept track of which rod caps go to which rod and what direction they were installed... They are machined as matching sets.

Crank looks used but I don't see anything bad there. Any scratches big enough to catch your fingernail and it should get machined.

There are specs for everything in the motor. You just need to find them and check. A good set of micrometers and a set of snap gauges can tell you almost everything you need to know.

Most of rebuilding a motor is cleaning parts and keeping them clean.


Thanks! I am rebuilding this one because I threw a rod in my old engine (hole the size of a silver dollar in the block). I bought this one for $400 and since it was already out, I decided to take everything apart to make sure it looks good before I put it in.

I don't have any history on the engine (miles, etc) - it came from a shop on eBay.
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post #5 of 5 Old 11-18-2019, 02:00 PM
zjosh93
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In that case, I'd probably run a light hone down the bores. If the stones touch all the way around, then the bore is probably good enough. Drop in a new set of rings and rod and main bearings. Don't worry about the cam bearings. Clean everything really well. Lap the valves. Check the valves for worn guides. Bolt it back together and call it good.
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