68 turbo Dart head gasket autopsy

[Dart270]

Got the turbo Dart head off on Sunday. Head gasket was well blown between #4 and 5, as expected, and was starting to go through from #1 to #2. Looked like pretty long term erosion, followed by a big blowout on that last pull. This was the Aussie ACL 3.54" bore gasket (0.042" compressed), not a Felpro. This is a cheaper design gasket, by my estimation.

The fire rings on those cylinders were slightly overlapping either the bore notches I cut in the tops of the cyls around the valves, or overlapping the valve relief areas in the combustion chamber (yes, I observed both). This is a slightly mismatched combo of a 1.76"/1.5" valve head on a 3.43" bore motor. You can see the gasket and head are not perfectly indexed on the block by the dowels. Other erosion or heat damage could be seen on other parts of the gasket fire rings.

Again, this engine config (w/ turbo @ 9psi and no intercooler) had been running fine for about 50 drag passes and 5-7 k street (beating) miles with lots of goofing around. 150+k miles on this stock rebuild short block. I am quite happy to see no damage to pistons or signs of detonation on chambers, plugs, or anywhere else in there.

I was hoping to get pics before my trip abroad, but I'm not seeing that happening soon.

Moral of the story: Don't let fire ring overlap combustion chamber. The ones that did not overlap do not seem damaged at all.

I will be putting in a Permaseal Aussie gasket (3.66" bore, 0.045" compressed) with ARP head studs. Should have no fire ring in chambers. We'll see how that holds up.

Cheers,

Lou

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Return of the 64 Dart. Hang on...

[slantzilla]

Thanks for the update/autopsy results Lou, and have a good trip.

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Proud supporter of Mike Jeffrey Racing Engines since 1999.