Can the piston hitting the head be noticed before it's too late?

[ELS]

Does it make a distinct sound, or something else that can be noticed before the piston or rod gets damaged?

[rebelrouser]

well if it hits hard the engine will not spin over, so I guess you are saying when the piston gets hot and expands it is barely kissing, my answer is no, it makes no sound I can hear anyway. Taken several engines apart and the size stamping on the piston was transferred to the quench of the head. And many times you get lucky and there is no damage. The thing is you have to check such things when assembling, modeling clay is really cheap and it just takes a few minutes to check piston to valve and piston to head clearance.

[dfarr67]

I've heard tell that some of the best running engines had piston witness marks on the head.

[mag2555]

The piston or rod gets damaged you ask!
How about piston to head contact negating the rod Bearing clearance.
Even if this is taking place just for a microsecond as rpm goes up your going to burn up the Bearing .

[Truckedup]

Heard knocking from some mid 70's Chevy 350 van engines...Carbon had built up to close the squish and cause piston to head contact..The sound was an obvious upper knock on a stock engine..

[DCal]

The piston or rod gets damaged you ask!
How about piston to head contact negating the rod Bearing clearance.
Even if this is taking place just for a microsecond as rpm goes up your going to burn up the Bearing .

Yup And it will use up the pin bore and rod bore clearances on its way to the crank bearings. Look at it as an interference fit.

[modok]

I'll be honest and say I don't know.
What I do know is the pistons lightly hitting the head causes no problems, and when that point is found...........9 out of ten dentists agrees to back off a bit rather than trying tighter.