Compression Ideas

[Bennyj]

 

Hey Gang,

 

I'm driving a 2001 GMC Sierra 1500 with a 4.8L V8. Looking for a little bit of help with a Compression diagnoses. Info is as follows;

 

Compression - 

115 - 8      7 - 110

110 - 6      5 - 95

120 - 4     3 - 115

115 - 2      1 - 95

 

Its not Burning oil, burns a bit of coolant but nothing noticeable out of the exhaust and the coolant doesn't look contaminated. there a slight knock/tic when i start from cold but only for the first couple seconds. No drivability issues but she does burn gas pretty decent of late. Had a misfire issues a few years back and replaced all the injectors not sure if that caused any damage. Theres a slight leak in the exhaust manifold. Otherwise it's runs great.

 

Was thinking of doing the head gaskets and valve cover gaskets and having a look while i was in there but i was hoping to get a few educated guesses to what i might keep my eyes open for. 

 

Thanks in advanced.

 

 

 

 

 

[CamGTP]

I've seen worse that is for sure. When something is that old it's tough to say if it's an issue with the rings or the valves aren't sealing as well on those two cylinders that are lower.

 

You'd have to do a leak down test to see what you come up with.

[Grumpy Bear]

Maybe you already did this but rerun cylinders 1 and 5 but time with a tablespoon of engine oil. If the numbers improve then rings. Argh....

 

If not the 'likely' valves. If valves then freshen the heads. Sometimes if it isn't horrible you can just lap them.