So that's not a factory stamping? What would make the valves lift further? Or is this a case of over rev and float?
I honestly don't know how or why yet. Waiting for the shop to call me so I can talk to the tech and see what he says.
Here's what he wrote me in the email.
I have the heads removed from the shortblock. Found something concerning, I've attached pictures for you to see.
Cylinder 3 and 4 pistons came in contact with the exhaust valves, cylinder 3 is pretty bad so that's the one in the picture. There is also some scoring on the cylinder wall in cylinder 3.
I measured piston protrusion and they are about .036" out of the hole. They should be in the .024"-.034" range according to manufacturer specifications. I usually set them up in the .026-.030" range on our engines to be safe.
This block must have had the deck surfaces milled at some point which is fine, but the pistons need to be machined as well, or use the .010" reduced compression height pistons that are available.
Long story short, we can't put this thing back together like this. Even if the valves are recessed into the head another .005", we'll still have a piston to cylinder head clearance issue. The head gasket thickness is only .059" so only .023" clearance between piston and head is just too tight once everything heats up and expands.
Once I talk to him and get more information I'll let everyone know.