I picked up a L59 out of a 2002 Tahoe for a swap and I've found some issues that I could use some advice on. I ran a compression test and cylinders 5 and 7 are low. When I found that, I pulled that rocker cover and the rockers for cylinders 1 and 3 have rust on them. It's enough rust that it probably needs new pushrods and possibly rockers but just for those cylinders. Is this a common issue for these engines? Just wondering if there is some common issue that I should be solving.

Also, am I a fool to think I can just pull that head and clean it up without a full rebuild? The oil was clean when I drained it, no water or gas or anything.

 

Did this engine sit for a long time, like several years? It would take a while for rust from condensation to form, as I’ve had it happen to me on the rockers. Usually a used engine has a good enough film (sludge) on all the parts to keep rust at bay.
How low are the two cylinders compared to others?

 

As best as I can tell it sat for 2 years or so. Really didn't even think about condensation as a problem. The other cylinders are in the +/-120 range, 5 was 100psi and 7 was 50psi. I'm suspicious that it's valve related.

 

Could very well be the problem that you have some surface rust on the valves of that cylinder. Condensation is a real problem unless the shop it’s in is climate controlled. Do you have a borescope to look into the cylinder? You can try spraying something like WD-40 (take it easy, not tooo much) in the intake ports, (pull the intake obviously if you haven’t already) and into the cylinder through the spark plug holes and see if the values change, but more than likely your pulling the heads for a better look.
Try turning it over with spark plugs out and valvecovers off, to visually make sure all the pushrods are moving like they are supposed to, especially the suspect cylinder.

 

I've got the intake off already. Does look like some rust on top of #7 intake valve. Looks like I'm pulling and cleaning at the very least.