The V8 Owners Forum -

The pressure I seen as an arbitrary measure to really put the casting through its paces as any weakness would have been exposed as the fault
Once I move over to adding heads to the test it leaked under any applied pressure.

I've checked the bolt insertion and even just hand tightening them in I can measure 4mm less than the head height so those are doing their job so to speak.

You could find a scrap engine (but in notionally working order), and try your tests on that. They might all leak at 80PSI!

Chris.

I've got another block free of repairs which has also kept 60 odd psi contained over night so that at least got a fighting chance of holding pressure

The thing with the current engine is the joint wouldn't hold any pressure long enough to get leak detector on it so I had to get it up to at least 50psi to give enough time to investigate it , and tbf the cylinder fire rings are no different in design to the sealing employed around the waterways.
I'll get to the bottom of it in a cost effective manner eventually , I pondered getting another separate engine but even a seized one on ebay went for like 170 odd quid haha

I had sealing issues with a V4 Honda bike engine that had stainless steel shim head gaskets ,I tried all sorts of poop on them to seal . Loctite flange sealer set hard as soon as I started torquing the head down and didn't squash out evenly at all.....in the end a guru told me "just clean em (the gaskets) and spray a bit of aerosol paint on both sides ,let it touch dry and Chuck em in " .....worked a treat.......and ,I confess ,I was re-using the old gaskets ( poverty is a bitch )

I was told by an old-timer to coat both sides of a head gasket with Indian Head shellac and then fit & torque down before it dries.
I have done this on petrol and diesel engines without comeback. Alternatively, copper based gasket spray will do.