OK so I got the cylinder head off..., ...But need some help understanding what I'm seeing. Options

[Nozzle]

Quick background: With 100k miles on the car, previous owner had motor rebuilt back in 1985. Engine now has about 30K miles and started blowing oil into the intake plenum bigtime and running poorly. I checked the compression and got 73 PSI in cylinder three with 145-150 in the others. Did a valve adjustment (most were slightly tight but not bad) and compression came up to 80 PSI in number three with the others staying about the same.

Dropped the engine today, pulled the head on cylinders 3 and 4 and here's what I found:

Combustion chamber #3 cylinder



Here's chamber for #4 cylinder for comparison



Not sure if it's related but exhaust valve spring for cylinder #3 was discolored with what looks like burned oil while the rest looked nice and shiny



Cylinder 3 piston and bore



And cylinder 4 piston for comparision



I'm thinking leaking rings on cylinder 3 is the cause of the oil in the plenum and inside the cylinders as the valves in that cylinder seem to look OK unless I'm mission something. Very interesting in hearing any thoughts as this my first time going inside the engine like this.

Thanks,

John

[Nozzle]

The rebuild was done by a supposedly reputable independent Porsche specialty shop in Santa Barbara, CA back in 1985 but I can already tell they didn't use all the new OEM parts supplied by the owner to them for the build. The reason I say that is I've already found mismatched rocker arms in the heads but I have receipts from PO which show a full set of new rockers delivered to the shop. Also other EFI parts on the engine seem to have been simply brushed with silver paint rather than replaced with the new part supplied by the PO. Not very encouraging to say the least.

My current theory is rings in number 3 are shot and they are blowing oil back into the intake plenum which is then redistributing they oil into the other cylinders. Is such a thing possible? Is there a way to determine if the rings or the valve guides are out to lunch? (IMG:style_emoticons/default/confused24.gif)