I have a caved in #2 cylinder and a torched cylinder head to deal with now. Not sure why this happened, but I remember the starter baulking once. So, did the gasket fail, then hydro lock the cylinder? Thats what i assume. Makes me wonder if the surface finish was right for cometic gasket?
The bad spot on the head is very shallow, like maybe .002 deep but still will have to be fixed. I hope they don't have to cut both heads to fix this. The block is fine on the deck surface luckily.

Did the gasket fail in the area adjacent to the crack in the cylinder?

Hard to tell by looking st a pic on my phone....... and it may not have anything to do with the failure........ but the machining marks in the gasket look coarser than what I’d do for a MLS gasket.

I’d also look at the relationship between the gasket bore and the cylinder bore....... to be sure the edge of the gasket bore was definitely not hanging into the cylinder bore...... at all.

The gaskets are 4.600 bore and very little chamfer on the deck.

Any chance you were too rich in that cylinder blowing the gasket?

Not sure what happened. It may have gotten too much fuel in the cylinder from the primerplus gasoline system. I have a 5 psi oil pressure switch for safety but also use an acumulater to prelube, which would allow fuel to pump into the motor if i turned the primerplus switch on before i prelubed.

So sorry that happened to you Greg, hope repairs go easy, Best Wishes

Thankyou Red. This sure isn't what i wanted to see. Head needs repair . block needs repair. Although i should be gratefull worse didn't happen.

Sorry that happened Greg. Good luck putting it back together.

Was it a new gasket or a reuse? Have seen a couple Cometic failures of late but with in the "firing ring" area of the gasket not a water jacket? The head surface finish sure seems a tad "rough" but could just be the pic..FWIW we actually use a bit of Hylomar around the water jackets on the ends. Hopefully wont be to spendy to get fixed up.

Did the raised embossing of the head gasket's compression ring area fall into an un-compressed area... of the head chamber? I've seen that on various engines ... and then the gasket cannot seal compression.

Also, it looks as though the surface finish is very rough... far greater than what is required for MLS gaskets (requires near glass-smooth... and sometimes the machine shops simply can't get that surface finish without spending careful time doing it... on both the deck and head surfaces, not just the head surface as is commonly brought to the shop).

I see corrosion around the rings in that cylinder in the last photo from sitting and maybe condensation in that cylinder while sitting, no cracks in a cylinder I see
Sorry for your problems, I hate Murphy

A couple of things; those areas that look like corrosion are actually depressions in the bore that are DEEP. And the one further down the bore is a crack you can catch a fingernail on. Also look at the fire ring of the gasket itself. It looks narrower close to the water jacket. That would indicate it wasn't squeezed enough ; improper(low) torque or a warped block? There is no corrosion anywhere. I cleared the motor with gasoline before putting it away for the day to eliminate corrosion.

FYI here are a couple pic of a recent failure on new gaskets with only a few runs on them, I belive 9? Was the second time in a short period of I'd seen it. Other failure led to a water jacket on the outside of the compression ring

That is from methanol laying in the cylinders.

I have seen that enough times over the years.

The only way I ever got that to stop is to put a gas primer on my car and run it on gas to clean the cylinders out at the end of the day.

Does running top end lube in the methanol help at all?
I see Greg did use a gas primer system, including at the end of the day to clear the engine.

Agree surface APPEARS a little rough...when in doubt, lap the surface. ALSO, i always use some type of sealer around water...anaerobic, hylomar, even pipe dough sparingly sometimes. I'm sorry for the bad luck here Greg. Hope you an piece it back together economically reasonable.

I can’t remember for sure if you have an aluminum block (I'm pretty sure you do) so whenever I do an all aluminum engine I torque the heads from the OUTSIDE in, not from the inside out. I forget who taught me that because it’s been 25 or 30 years, but it’s still the way I do it.

Iron megablock.
I don' t think it is going to be cheap😢we will see.

Ouch! Strange.
An iron megablock that cracked a cylinder.
Is that near the bottom of the cylinder?

No Jim, it is closer to the top.
Al, new gasket. I was told it could have been caused by a register dowel being too tight

Is that a end cylinder or not?
I have had a bunch of stock blocks sleeved for different reasons, I ended up learning that you can sleeve a block like yours two ways, pressed in with a press in interference fit from .0025 to .0040 or chilling the sleeve in dry ice and heating the block up enough to allow the cold sleeve drop in or be push in by hand with a .00010 to .0010 interference fit. The pressed in with the tighter fit can and may affect the cylinder wall shape on the cylinders beside it which may need a lot of honing to make them round again . I now plan on installing all four sleeves on the side needing the sleeve unless I'm going to have it bored and honed to the next over size and buy new pistons
Either way make sure and use a good sleeve sealer on the sleeves that go in all the cylinder that have cracks in them

Thanks Cab. I have decided that it makes sense to go to a new block. I have always wanted to go aluminum and i am using this as my excuse. I assume there is some value in the megablock since it can be sleeved.
I talked to Todd at Marsh performance and have my name on a World aluminum block that is on its way to Todd.

Sonic the cylinder. My bet its thin. It split, let water in that cylinder and coughed the gasket due to rough deck surface. Could have been worse. Hydro locked and taken out the rod and block.
Doug

Again, there is no corrosion in the bores. This motor has never been shut down for the day until it was run for several seconds on gasoline and still very warm, like above 180. It had dyno pulls on it and eight passes total after being honed and reringed. What may look like corosion is a depression you can feel, it is that deep. The cylinderwall colapsed.

as to the tight dowel register fit, i think that would have been caught during assembly ?

I dont think lube makes much of a difference Jim.

They are more like stains that look worse than they actually are.

I found that just shutting the alky off and running on the primer isn't enough. Seems like fuel will still be left in the barrel valve, lines and nozzles and drain and drip into the engine. After I have run mine for a few minutes I blip the throttle several times before I shut it off.