No rush, just curious. Sunnen makes good stuff.

I am done posting about this, wanted to find answers and ideas I got them, for now..

Please explain........

In response to BB and MER:

Pre ignition maybe ?

Intake valve is well closed well before + after combustion event (BTDC and ATDC)

'A combustion event as intake valve opens or is closing, to me, would be pre-ignition.

There is a reason Manley suggests their "severe" duty intake valves, and "extreme duty" valves on a marine application. Its because of the heat, and tensile strength of the valve, and its fatigue life. If heat was not a factor for an intake valve, there would be no need to upgrade material. The severe duty intake valves were tested at temperatures of 1000, and 1400*.

Just because the valve gets fresh air and fuel passed over it, which greatly helps cool the valve, there is still NORMAL combustion temperatures of 2500+ degrees in the cylinder, and can be 2 times that during a detonation event. The intake valve is part of that puzzle. Contrary to popular belief, the intake valves do see high temperatures. Not as high as the exhaust obviously, but they certainly dont run "cool".

There is a reason high performance engines, need intake valves that are of a material that can handle higher temperatures. If in doubt, Call ferrea, or manley, and see if they tell you intake valves see less than a couple hundred degrees of head/stem temperature.

Pre-ignition is what I really meant Mark. Most people these days call it one in the same. It is two seperate things for those that don't know. One is from the light before and one from the ignition after.

In post #201 he states that the lifter is stuck in the bore. My money is still on that, FWIW. If the valve stuck in the guide, is it typical for the lifter to also be stuck in its bore? On the other hand, if the lifter gets stuck in its bore, then the valveguide is also going to be damaged when the piston comes up and whacks the valve face. The only scenario i can think of where the lifter gets damaged by the valve sticking in the guide would be if it sticks halfway open. But I'm not an engine builder - those of you who have seen multiple failures like this can weigh in on it. I'm just curious about what led to this. Hopefully we will all get an answer at some point, and the OP can get some help getting his motor back together.

Debris from destroyed valve will also stick a lifter.........

Maybe it is in a post somewhere that I missed, but what does the pushrod look like?

Valve seized in guide lifter took up slack tried to open it more and spread the lifter apart at axel from over loading. Valve broke and That's why lifter was stuck. Just a guess