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What's the thinnest b230 Cometic you've run?

You can also spend $30 at HF and get a dial indicator and magnetic base. Not the best, but they'll work.
 
Just use the timing marks on the front pulley (although beware of loose/rotated outer sections of the harmonic balancer). A flat edge and some feeler gauges will work just as well - measure along the center line of the engine - not on the sides. The pistons can rock a little in their bores and you don't want to be measuring that. Actually, that piston rock is probably why there is the recommendation that you try to get it to .032" or so... but no closer. Any closer and the piston might rock a little and tap the head occasionally.
 
So what's the compressed thickness of a Mahle B230 HG?

It measures a wopping .0538" new in the box.

From another thread "The SAE says less than .036 does not produce significant gains"
That is talking about piston to head clearance no matter what you call it.

Did not intend to start word games.

I'm pretty sure that piston damage pictured was due to detonation.
So what came first the hot spot or the detonation
Detonation causes hot spots and or spikes cylinder head temps as well as melting pistons.

IMG-1810.jpg
 
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That is an Ironhead Sportster piston and the damage is due to a combination of stupidity and a bad tuneup.
I'm fairly certain the guy who did that was in a somewhat altered state at the time.

Ironheads have a HUGE open spherical combustion chamber with the valves at 90? from each other.
The piston has a wedge shaped knob on it that fits between the valves to get the compression up somewhere usable.

That is my favorite detonation picture! Here is another. From a Shovelhead.
IMG-1774.jpg
 
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