MattP

I was replacing my intake valve retainers (two showed signs of major cracks) in my 03 AP1 and neglected to attach the air hose for cyl #3 so a valve dropped into the engine. I started to remove the head, and got to the point where the intake manifold was off. I was able to lift the valve back into the head. Unfortunately when I checked, 7 of the 8 intake valves had quite a bit of air leak around them. I knew it had been over revved prior to my ownership and had been counting on possibly rebuilding the head so I finished pulling the head.

Unfortunately some debris had been in the #1 cylinder and scored the walls of the cylinder and damaged the piston and head before they were ejected. I believe I may have done this after the compression test I did a month and a half ago. A plug was damaged putting it back in. I did my best to get it out and hadn't been having any issues until recently when I got a misfire on various cylinder code, and I went to do a valve adjustment which started this whole thing. In any case this is what it looks like now:





I know the block is done and I will need to find a new one. The scores are deep enough to catch a fingernail. Can the head be saved? What parts should be replaced as part of the rebuild if it can?

Slowcrash_101

Does it run the full length of the cylinder? You have .25mm to bore out the cylinder. Are the scratches deeper than that?

MattP

No, they're quite shallow. That said, I thought the FRM bores aren't machinable/honable by most machine shops and a used block is more economical.

Slowcrash_101

Depends, if the shop in question has experience with Porsche motors, they will likely have the equipment necessary to rebuild an fxxc1 because a lot of Porsche engines also use an FRM coating on the cylinder liners. If not, there's people here on the forums you could ship your engine to and they can rebuild it for a very reasonable price, in any case it'll be cheaper than a new engine.

windhund116

You know, looking at that one exhaust valve and the pattern of the marks on the cylinder --- looks like evidence for the engine temporarily seizing. Not foreign objects in the combustion chamber. Maybe good to figure out why this happened, before rebuilding or replacing.

MattP

I know what the issue was, it was a piece of spark plug insulator. I started to tighten a plug with a piece of he compression tester still in the hole.

I cleaned the best I could (grease on rope, long q-tip type things, etc) and checked with a boroscope to verify all clear. In retrospect there were likely pieces caught on top of the rings and I should have pulled the head then. The block was probably fine or close to it at that time.

I think what you are seeing is carbon on the valve combined with dirty oil from pulling the head.

windhund116

I see one exhaust valve that has a whitish residue. While all the others are dark-brown. This can be a sign that valve overheated. Local overheating may lead to uneven expansion of the piston. Possible seizing condition. If you look at the cylinder wall, there appears to be aluminum deposits. This is prolly the piston skirt depositing onto the walls. Transfer of aluminum from piston to wall.

Anyhow, if the some of the damage is ridges and not valleys --- do the feel test again --- then, engine seizure should be ruled-out. Must inspect pistons.


Just IMHO. 2¢ worth of 2¢.