I think I figured out what killed my engine. And it’s a new failure mode that I hadn’t heard of before.
If you look closely at one of the intake ports where the cylinder didn’t have an issue, you can see that there’s a bright line of clean aluminum where the gasket was.
https://adobe.ly/3lzIlzc
If you look at number 2, the cylinder that failed, the bright clean line goes all 3/4 of the way around but closest to the center of the engine there’s dirt all across the clean line. Looks like there was a vacuum leak from the plastic intake manifold warping. All the bolts were tight, nothing was loose. Yet there was not a good seal.
https://adobe.ly/3Cbidkw
Since I was a autocrossing the car, there was sustained high rpm usage so that vacuum leak caused cylinder 2 to to get hot enough to drop a valve.
How do I prevent this from happening again? Not sure yet, I’m going to see if the new seals are thicker than the old ones perhaps, I might run some extra sealant around outside the factory seals, not inside. I’ll probably trash that intake manifold and buy another used one but what’s to say the new one won’t be already warped or warp after I put it on.
Food for thought.
Silber
Threaded Mode
