ULOS2A6

I have a 2008 SS. The engine misfires at low rpm and a loss of power.
Upon doing a compression test here is what I found. Cylinder 1--110, 2,106, 3--118, 4--50. It doesn't get hot however a few months back before the misfire the fan module went out and the temp reached 250+ before I noticed. It cooled right down on the freeway. The misfire came a month later after I replaced the fan module. I am suspecting bad valve seats or a bad head. Has anyone replaced the head themselves and if so how long does it take?
I can get a new GM head from ZZ for 300 dollars. Anyone have any ideas if this is the proper route to repair the engine?

donbrew

Don't remember for sure, but 170 psi rings a bell as proper.
Suggesting either much worse diagnosis or operator error.

andyb

cylinder head replacement time per alldata is 15.7 hours!

prod

Best bet is to get it inspected by someone that knows these engines before attempting any repair. Good bet its the dirty valve syndrome but could be a number of other issues, perhaps a head gasket damaged by the overheat. With the possible cost involved a proper first hand diagnosis is key here.

gamma-wes

Sounds like the head gasket if the original symptom is an overheat. You may have warped the head, but not likely. You could have a dropped valve, but not likely.

Your best bet on that spread of compression numbers is to pull the head and explore. You can pull a leak-down test, but I doubt you have that equipment just laying around. Most personal garages don't. When you pull it, you'll be able to tell by the head, block, and gasket if there is an issue with the head gasket pretty quick. If there are any valve/spring/retainer issues, you'll be able to tell pretty quick too.

I always take the head(s) down to a decent machinist to look them over when I do any heads-off work on a car. 9 out of 10, no serious milling work or damage. The job is going to eat up a weekend if you plan it right. It will eat up a week or two if you don't.

With that much compression loss, you should see issues with burning oil or coolant, though it's harder to tell with turbocharged applications. Let the car idle for a while and then take it for a ride. Immediately after you spool the turbo, your exhaust should be either white or blue smoke. White=coolant, blue=oil. If you don't see anything, either the gasket leak isn't that bad or you aren't in the category of a new head gasket. You may have bigger issues.

paperboy72

check ebay on the cylinder head, believe zzp had one complete and not complete on there, not complete was like $100, complete was about $300 if I remember right
just and fyi if that is it