Topic: eating oil, puking smoke

[Hockey1]

my 90 2.5 just recently started sucking up oil like crazy. i drive it maybe 100 miles a week and now need to add 1-2 quarts of oil a week. it smokes bad but not all the time. mainly at idle or very low rpms, especially pulling out from a complete stop. i changed the air filter, pcv valve and breather. along with having the valve cover replaced cause it was warped and leaking. if you remember from a previous thread of mine, it originally had a cracked block that i replaced with the rear main seal and freeze plugs. now it doesnt leak a bit of oil. its going to the garage next thursday, but my mechanic always says "just sell the damn thing". not sure what to expect as a diagnosis. bad pistons, valves who iknows. but i did see this from quadratec and wondered if it would help at all.http://www.quadratec.com/products/product_search.php?kw=51108.101&submit=Go%21 what do you think? if anything it might give me a little umpf. if the compression test is bad, would this fix it? i know its not a racing engine but highway speeds and 5th gear would be great. oh its stock pretty much everything and pushing 31" tires, at 13 mpg. any ideas?

[Jeffy]

You want to do a compression test on the engine.  Check the spark plugs for oil.  How many miles does it have?  I'm guessing 150K or more?  Easiest thing would be to get a 2.5L from a later YJ or a TJ then swap it in and reuse your intake and keep it TBI.

[Hockey1]

when the block cracked i found a motor out of a 93. i wanted to keep my motor, and just swap blocks.  it ran great for 9-10 months. although it never seemed to have as much power as before. my original motor has 106xxx miles on it. we only swapped the block that i know of.  cause i have the other cylinder head in the basement.

[chardrc]

since you recently got a new block id say its probably the valves... but as previously stated start with a compression test and go from there.

[aw12345]

atleat a compression test but if you have acces to an air compressor a cylinder leak down test is the way to go, Harbor freight sells an affordable leak down tester. Its a lot more work but gives you a much better idea whats worn without tearing the engine down.  To do the test each cylinder has to be at top dead center with the valves closed, also disconnect the pcv system of the valve cover then note the percentage of leak and listen as to where the presurized air goes, i.e exhaust, intake or out of the oil cap. Also if you have abad pushrod or rocker arm on a intake valve it will suck oil like crazy or one intake valve not opening due to a flat cam lobe

[Hockey1]

The garage said that he is going to do the compression test. My qusetion is if I need to get it bored out, which I probably will anyway. How much do machine shops usually charge? My last motor was bored out 60,000 or however you say it. I could really tell a difference when I swapped blocks. I want to replace the cylinder head with the one from quadratec. I dont really want to do another motor swap. Just fix the heep I have now.

[Jeffy]

You really need to test it first.

When you say your 'last motor was bored', you mean the one that's in it now or the original block?  What's the mileage on the Jeep and the current engine?  What was the reason behind reusing a high mileage head from your original engine rather then using the matching head from the new block?  Was the new block rebuilt in any way before installation?

Typically when rebuilding an engine, you do the minimal amount of work to get it back into spec.  That would mean not jumping straight to .060".  The bare minimum might be new rings and a hone.  You'd want to block hot tanked to make sure all the crap is out of it too.  I'd have the matching head hot tanked, then have it magnafluxed.  Then get both the head and blocked decked if necessary.  You will need to talk to your mechanic.  I'd check the block while the head is off.  Don't do it halfassed or else you'll spend more having to tear into the engine again.

If you wanted inexpensive, then you'd want to go find a engine out of a TJ or XJ with low miles and swap the whole thing in.  That's probably the cheapest option and the fastest.

[Hockey1]

Okay, just so everyone understands. I have very little experience with engines. It's like teaching calculus to a 1st grader. It can be done, but its not easy. With that said, I'm on the learning curve here. So all help is appreciated and needed.
My original block was bored .060"., but then it cracked in a major way. So when I found a motor online I got it. The guy wasnt sure what year it was out of, 93 or 95. He bought it for parts and was selling it out.
 So the mechanic kept the original motors top half cause he said I would have to replace alot of parts if I didnt. Water pump and things of that nature. Again I took him at his word, because I was clueless. I had already replaced waterpump, alternator, belts, IAC, and just about every other part on it. So he only swapped the block.
The original motor had 100k on it. It now has less than 5k on the "new" one. I dont want to get another used motor and worry that it wont last long either. So i figured rebuilding this one, even though its more expensive, would be more cost effective in the long run.
Other people have said it might need rebored if the cylinders are bad. So wouldnt a rebuild and boring be necessary? If the cylinder walls are defective or damaged, is there another option?
I do know that he had it magnafluxed. I paid that bill directly to the shop and spoke with the guy that did it.