Loss of controlled burn or pressure spikes often compromise the fasteners and "lift" the head off of the block and or gasket , usually resulting in gasket failure. We used to think of it as poor gaskets but now realize it it poor "burn management" LOL. If the fasteners aren't compromised , the next sacrificial part is the piston which more often than not is blamed but not the actual problem.
Randy
You mean it's not always those "cheap" OEM torque to yield bolts that was the problem!!!??? If you are terrible at tuning use cheap head bolts LoL
I used to be a Test Engineer at a snowmobile and ATV manufacturer. We used all piezo-electric pressure transducers to monitor cylinder/combustion pressure. Along with monitoring crank and cam position to the .01 of a degree, valve position with laser transducers to catch any valve float, and strain gages on each of the petals of the reed valves (2 strokes), it was amazing how much data you could gather. The flutter experienced by the reed valve petals on an 800 cc 2 stroke turning 10,000 on the pump always fascinated me. The fact that we could see that movement and graph it precisely in relation to crank position, cylinder pressure, injection timing, or any other wide variety of variables helped dial these engines in precisely.
It was not unusual to record data at 100,000 Hz or more to see exactly what was going on. Then again, these were $3,000 pressure transducers plugged into $80,000 Data Loggers running inside $3,000,000 AVL AC drive dyno cells. Definitely not your shade tree mechanic level stuff.
I haven't data logged a 2 stroke and watched cylinder pressure and never had the stuff to watch the reed petals. All of that stuff I did mostly on diesels and a few push-rod V8's just for fun while I was figuring out how to run all the electronics. I did race snowmobiles and quads for a quite a long time and even without an impressive graph data logging the petals I have an enormous amount of respect for what those reed can do.
The pressure transducers I was using, I'm sure they're are better versions now, were also piezo's good to 5k psi but they had a very definite life span and it wasn't as long as you would want (at least not when you have to pay for em!).
But really, when you consider the cylinder pressure, temperatures and everything else that's going on in a push rod engine even at 5000 rpm it's pretty impressive on a basic level of what the material can handle. Especially when you compare it to what we had available 75 years ago, or even 20. I doubt many people driving their 100hp hotrod A or B model Ford's around would have thought it was common to see 500-700hp cars on the show room floor.
