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ZJ Engine overhaul questions

My 97 ZJ needs an engine overhaul--has a cracked ring (or worse). I'm debating my options. Pulling the engine, overhauling it myself, and putting it back is out--with the engine out of the Jeep I wouldn't have any way to get the block to the machine shop. So I'm debating whether to

(a) get a rebuilt long-block and put it in and be done with it or (b) get a junkyard engine, rebuild that, and put it in, or (c) get a junkyard engine, put it in, rebuild the existing engine, and swap it back. (d) get a beater pickup truck and use it to haul the block to the machine shop and back and once the job is done sell the beater.

Before I spend money I figured I'd see what others thought of the options.

Reply to
J. Clarke
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what makes you think it has a cracked ring? Just wondering because the valve springs on that year had some failure issues.

FWIW,

SHORT BLOCK, All Models - 4.0L - 4.0L 97-98 $1,903.50 Includes: Block With Pistons, Rings, Pins, Rods, Main Bearings, Crankshaft, Camshaft Bearings, Timing Gears And Timing Chain.

SHORT BLOCK, 5.9L - 5.2L, 5.9L - 5.2L, 5.9L 97-98 $1,964.25 Includes: Cylinder Block With Pistons & Rings, Crankshaft, Connecting Rods & Bearings.

no core charges, and that's from chryslerpartsdirect.com, OEM.

Reply to
DougW

Symptoms are (1) one and only one plug is getting oil-fouled regularly, (2) low compression on that cylinder, (3) engine is using a lot of oil, (4) blows small amount of blue smoke.

Good to know. I'm a little hesitant about a short block--the engine was run oil-starved for a while (don't ask) and I'm betting that the valve guides aren't pretty. Could do the top overhaul but that would mean more downtime.

Reply to
J. Clarke

To me that sounds like a worn valve guide allowing oil to get sucked down in from above.

Have you tried a squirt(teaspoon) of 30W oil into the low one? If the compression goes up, it's rings. If the compression stayes the same, it's valve or possibly head gasket. But if it was the gasket you would have other symptoms.

Also if you have a vac gauge, see if it matches any of the problems shown here:

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Reply to
DougW

BUT is he has a busted oil ring but the compression ring is OK that test won't show it... although if it's lost compression because of a busted compression ring scoring the cylinder the test would show that.

How about a cylinder leak down test? Then you can hear if the air is escaping into the crankcase or into the intake or exhaust.

Jeff DeWitt

Reply to
Jeff DeWitt

Actually it would show if you read data right. if oil ring is busted (very unlikely) there would not be much diffence in wet/dry readings. Something else to consider here is a stuck ring. I have seen this in a lot of cars especailly some GM models. Extended, infrequent oil changes or wrong oil grade is the main cause of stuck ring issues. If engine has not been serviced often I would consider this and if so this is curable without a teardown.

----------------- TheSnoMan.com

Reply to
SnoMan

I am curious as to how one would cure a stuck ring without a teardown.

Reply to
J. Clarke

You can remove the spark plug and pour a solvent into the cylinder and let is soak for a few hours or overnight, then pour some more, wait a bit and run it. I have had good luck using carb cleaner, penetrating oil and have heard a soak in kerosene will also loosen it.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06
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Reply to
Mike Romain

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