CamoKing Posted June 10, 2019 Report Share Posted June 10, 2019 (I'd been driving this truck for only about two months. I know little of its long standing history other than it was used and abused.) This is what I saw after pulling a Z22 head from an '82 720 King following gasket failure. What does all this pitting due to?? Detonation? Is this piston headed for failure? It is mostly on cylinder 4, but 3 shows some, too. I've also discovered that the intake valves are slightly bent (all 4, about the same). I can 't really do anything about this but I am wondering if it is worth proceeding with this basic head-job and putting all back together. This is chamber #4 of the head. Quote Link to comment
Stoffregen Motorsports Posted June 11, 2019 Report Share Posted June 11, 2019 Those pits are from debris. Probably a spark plug tip got hot and broke off at some point. I have seen worse. Basically, if the rings still move on the piston, it's probably fine. Sometimes, a foreign object bouncing around in the combustion chamber will cause the piston ring land to squeeze down on the rings, rendering them useless. 1 Quote Link to comment
GT2 Posted June 11, 2019 Report Share Posted June 11, 2019 How do the cylinder walls look? Quote Link to comment
datzenmike Posted June 11, 2019 Report Share Posted June 11, 2019 Maybe even a piece of the fire ring on the gasket, if that was where the gasket failed. Put the valves back in to protect the seats and lightly sand or wire wheel any sharp edges off. Only takes a few seconds. Carbon will fill in the pits. Lightly wire wheel the carbon off the ports near the seats too. This won't have hurt the piston, they are about 15% 'glass' and very hard. How are you determining the valves are bent? Quote Link to comment
CamoKing Posted June 11, 2019 Author Report Share Posted June 11, 2019 13 hours ago, datzenmike said: Maybe even a piece of the fire ring on the gasket, if that was where the gasket failed. Put the valves back in to protect the seats and lightly sand or wire wheel any sharp edges off. Only takes a few seconds. Carbon will fill in the pits. Lightly wire wheel the carbon off the ports near the seats too. This won't have hurt the piston, they are about 15% 'glass' and very hard. How are you determining the valves are bent? Following lapping, light slivers were observed when viewing valve closure through ports; then I set up a jig with dial caliper to confirm the lack of concentric-ness (?) The fire ring of the old gasket is definitely broken @cyl.#4 but not anywhere else. I'm guessing this pitting occurred before I got the truck. I imagine that such a thing would happen very fast. Quote Link to comment
datzenmike Posted June 12, 2019 Report Share Posted June 12, 2019 Maybe the valve guides are worn oval? Quote Link to comment
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