Need a little help with compression test diagnosis

[nonickatall]

I don't understand why you go to a shop to rebuild cylinder heads, if you yet not know the problem.

I mean, there is nothing to say against rebuild or tune the LS engine, but as far as i understood, but that may be wrong, due my limited knowledge of the English language as a German, you had the problem of finding the reason for your P0308?

So i would first find the problem, if you have money and fun to invest in your engine then rebuild, tune, or whatever...

By the way, it can also be a problem of a clogged cat. I had that a a BMW 4cylinder, where only cylinder 2 had misfire and after a compression test, which was fine, and checking ignition and injection, which where also fine, i disconnected the exhaust and the engine run like it should. So i disassembled the cat and everything was fine

Why ever the clogged cat only affected the engine control to find problem on cylinder 2.

 

[Eldiablo]

Hey guys, I have a 2001 Tahoe LT with the 5.3 L Vortec LM7 engine ("T" VIN code) and about 150000 miles. Two weeks ago the engine started misfiring with the P0308 code. I also heard a loud ticking from the engine bay, so obviously I supected, that something with the lifters has gone bad. Also the ticking came from cylinder 8.
After taking off the valve cover and fiddling with the rockers, I saw, that the second rocker from the back was moving about a 1/4 inch up and down. So I'm guessing the lifter for this valve has collapsed.
Before taking off the cylinder head I wanted to check the compression and here are the results:

Cylinder	dry	wet	difference dry to wet
1	130 psi	135 psi	5 psi
3	137	145	8
5	132	137	5
7	131	140	9
2	130	150	20
4	115	135	20
6	127	150	23
8	125	137	12

This is the first time, I checked the compression on an engine, so I wanted to ask you guys for help. Do you think I should replace the cylinder heads, according to these numbers?
Since I already have to take them off, I wouldn't want to reuse them, if they were bad. Of course I still have to check them, when I have taken them off, but I thought the compression test would be a great help here.
From what my Haynes repair manual tells me (minimum compression pressure 100 psi; maximum variation between cylinders 25 % from the highes reading), I would be guessing, that these values should be OK-ish. The lowest value is 115 psi for cylinder 4 (so 15 psi above the minimal pressure) and the variation from this to the highest reading would be about 16 % (22 psi difference from the 137 psi reading of cylinder 3).

What do you guys think? Would you recommend getting new cylinder heads, by looking at these numbers? Or would you rather save the money and reuse the old ones?

your problem is worn out rings not valves. Take the heads in have them checked surfaced valve job put it together and run it. Thats low compression for that many miles. Change your air filter more often.