Freefallin

So i bought a used LS1 motor from the junk yard and unfortunately, i think i will have to return it back.

Motor smokes ALOT when i accelerate hard. It does that only at high rpms. However, i think this is not from the engine but rather from the oil filled exhaust system.

My previous engine had a couple of really bad piston rings. Oil used to literally drip from the exhaust and i used to put a quart everyday. Drove it like that for about 3 months. So now i figure when i rev the engine hard, the heat is burning the oil in the muffler/exhaust system, hence the blue smoke. To be sure, i disconnected the exhaust pipe at the headers and reved the engine a few times...no smoke at all.

However, after the above test, i did a compression test. When i pulled out the spark plugs, only one of them was oil fouled, the rest were only a little "ashy". Compression test for that cylinder was 185-200. Whereas the rest were between 174-176.

What does this mean?

Freefallin

Wow! Is it that tough of a question

jarjarlol

Leak down and compression test then try them with a spoon of oil. Problem found.

Exidous

iTrader: (11)

Since your one cylinder that had the fouled plug is showing HIGHER compression than the rest I'd be willing to bet you have a bad valve stem seal on that cylinder. You are leaking oil into that chamber and are essentially doing a "wet" compression test giving teh higher numbers. I would not return an entire motor for that. 241 heads are stupid cheap. And it may just be the seal under the valve spring. I'd do a little more investigation and then talk to the junkyard. See if they'll cover gaskets if it is the seal.

Freefallin

I figured the same but could it be that the compression ring is OK hence the compression being OK but that the oil ring is bad and allowing oil into the chamber hence the high compression similar to what it would be when doing a wet test?? Make sense?

ss performance

iTrader: (17)

Go with simple first, don't jump into the major stuff until you have eliminated the simple.

The valve seal is simple to replace. short version remove the rockers, use an air fitting to put air into the cylinder, compress the valve spring and remove the locks, remove the spring, remove the bad seal, then reverse the process.

The type of vehicle will effect how long it takes F-bodys are a little more difficult due to the engine set back.

If you are going to do one you might as well do them all.

I'm sure you could fine a detailed how to somewhere.

Good luck.

Exidous

iTrader: (11)

It certainly can be the oil skirt but I'll replace a stem seal over an oil skirt any day. :-)

Worth a try before you return the motor.