I have a LQ4 with unknown miles, had issues with heads. Before I took the heads off, I did a compression check, 6 cylinders were about 150psi, the other was 120, that cylinder had some carbon buildup on the valve seat. The last one had a valve spring break. Should I hone the walls out and put in new rings? The cylinder walls look great, I can still see the factory hone. Also, some of the cylinder walls have some discoloration, from water, no pits, just some strains.

Now for the bottom end, I want to check out the main and rod bearings.
Are the rod bolts torque to yield, and what about the main caps, are they as well?

Thanks.

 

only the head bolts are TTY.

 

Rod and main bolts are not TTY, but they do torque to an angle. I've reused them successfully in a few builds.

If you have it apart, I'd go ahead an bump the hone through it and use new rings. You can use a brush hone or have the machine shop do it without a torque plate without removing much material from the cylinder walls. If you are planning on replacing pistons, have it torque plate honed to the next bore size.

 

compression tests should be run at operating temp. was yours done cold?
try a leak down test to see where you are losing pressure. It all might be in your heads/valve seal