Head gasket failure - Fire rings crushed?

[Nut124]

Asking for a fella on another forum. His Fiat twin cam head gasket blew under load in an uphill.

The fire rings of the gasket in all 4 cylinders are crushed flat as if hit by the pistons, all the way around. Piston contact was ruled out though due to the size of the bores in the gasket.

Detonation? Pre-ignition?

The engine had cranked 150psig. Plugs came out clean w white insulation. One plug had what looked like molten aluminum specs.

[rp930]

Looks like detonation to me.

[mag2555]

White plugs and clear signs of detonation will do that.

I would check the rod bearings now.

[biskma]

Just like to realize if four.10 whats advertised is after overwhelmed like compression thickness is. If it is I will miss a nick from the die grinder lol. Using it on a four.030 bore, do not need all of the compression either.

[BOOT]

Do you have a new unused gasket to directly compare/measure to the blown gasket fire rings? I am no headgasket expert and there are obvious other problems but that is not what you asked about. Again not a gasket expert, don't know what material those fire rings are and if maybe they got real Hot and sorta oozed/squished/grew. No clue if that is a thing but maybe some on here would know?

[mag2555]

If I hedge a bet that the motors exh valves are next to each other per cylinder would I loose?

[biskma]

No crushed is .047, the hoop diameter is four.10. I even have a scratch at approximately the four.05 a part of cylinder head deck and do not need to mill if don't must. Trying to convey compression down as well.





192.168.100.1 192.168.1.1

[allencr267]

If I hedge a bet that the motors exh valves are next to each other per cylinder would I loose?

Lose.
Fiat 124 Twin Cam, Hemi head, 2nd ever belt drive after the Pontiac OHC 6.

It might be the pics, but to me it sure looks like there's overhang in the cylinder and/or chamber.

[rfoll]

Those motors are notorious for blowing head gaskets.

[Nut124]

If I hedge a bet that the motors exh valves are next to each other per cylinder would I loose?

Lose.
Fiat 124 Twin Cam, Hemi head, 2nd ever belt drive after the Pontiac OHC 6.

It might be the pics, but to me it sure looks like there's overhang in the cylinder and/or chamber.

What do you mean with overhang? Fire rings too small for the bore?

[allencr267]

Yes.
The pic looks like the ring has upturned edges & curled back, like it was exposed to detonation while not compressed fully in contact with the head & block.
The piston's head/top land will be smaller then the bore, so " Piston contact was ruled out..." still may mean that the gasket is too small & protrudes/overhangs into the bore.
Any chance a head swap has wound up with a larger chamber?

[mag2555]

Aluminum shinny balls seen on a plug is a firm indicator that two flame fronts as in knock has blasted material of the pistons and also the heads if there aluminum.

If the motor was run on leaded race fuel these shinny balls would have a purple tint to them.