My plan is to use a borescope to inspect the piston. If I see damage inside the cylinder, I'll pull the entire engine. If I don't see any damage in the piston, I'll pull the head & re-inspect the piston again when the head is off.
Since you will be pulling the head in either case, why not just pull it first?
Good call about the piston reflecting onto the cylinder wall! That's exactly what it is, and it's obviously now, when looking at the pictures.
I pulled the head and verified that the cylinder wall is undamaged.
I had a single broken valve spring, which I'm now trying to diagnose...
I do have an aftermarket cam in the Pontiac 400, but I'm not sure what the actual profile of it is. The aftermarket cam was installed by a previous owner. The only legible markings on the cam are "CWC" and "540 233". I've searched the internet for those numbers, others have the same cam, but are unable to determine what it is.
I didn't have time to remove the cam from the block, but I did measure the lift of the cam by measuring the movement of the lifters as I rotated the engine by hand. It appears that the difference between high & low for the lifters is approximately 0.295'', which, assuming a 1.5 rocker arm, translates to about 0.4425 of valve lift.
What is the maximum amount of lift that the stock valve springs can handle? Would ~0.4425'' of valve lift potentially be enough to destroy a valve spring? Or am I looking at a freak event?
The valve spring failed after about 3000 miles of driving since the last rebuild. I do not know for sure if the valve springs were replaced last rebuild, but they do at least look to be in new condition.
