Valve cover gasket explosion:

[Erik Morris]

1971 383 brought to life after a 20+ year snooze. Engine has been idled for a max of 10 minutes across the past few days; 1 minute here, 2 minutes there.... oil pressure in the low 30s. Has started right up each time previously.
Ran the motor for 1 minute today, verified some gauges, shut off. Attempted a restart 10 minutes later and the right side valve cover gasket blew out explosively...sounded like a shotgun went off in the garage. Valve cover is physically bowed out from the pressure. Wife ran to garage to see if she was finally going to get some life insurance money.... is not impressed with my garage shenanigans. Removed valve cover gasket is (minimum) 20+ years old and in shabby condition. Oil breather is NOT clogged, flows freely. See pics.
Anybody ever experienced something like this? Valve cover is removed. Anything I should be checking/eyeballing before I throw new gaskets on and try another start?

 

[SattyNoCar]

I've seen valley pan gaskets do that from gas, gas/fumes in oil. When was the last time the oil was changed? Running it such a short period of time, it may not be getting up to temp to burn things off.

 

[zyzzyx]

I'm gonna go out in left field on this one, so please excuse me! Once back in my race days
we blew the oil pan off the car and did the same thing to our valve covers because of a hole burned in the piston.
Gas could have gotten in the oil pan and combusted???? Something unusual made your valve covers "Explode"!

 

[1968rt]

I blew out the valley pan and the valve covers from a hole in the piston. Sounded like a grenade! do a compression test. If theres a hole you will know right away. Maybe from sitting gas leaked into the pan? PS your rocker shafts are on upside down.

 

[zyzzyx]

Good call on the rocker shaft 1968rt!

 

[33 IMP]

I didn't catch it, but 1968rt is absolutely right!

 

[Fran Blacker]

I'd do a compression check if ok change the oil. Don't do that minute a couple minutes here and there unless there's a reason you can't warm it up.

 

[Erik Morris]

Thanks to all who have weighed in thus far. Oil was replaced prior to start. Water pump leaked badly and was replaced as well. No indications of any water in the oil or oil pan, and no oil leaks during prior short runs. Motor had one run on it just long enough to verify the thermostat opened and was shut down with temp at 182. Moving to compression checks. I know what follows if the compression check(s) fail....what would be next if they are good?

 

[AMX364]

Most times water does NOT burn. Gasoline does, car sitting years look for fuel pump leaking. Most likely cause and effect.

 

[Tinker67]

Oil full of fuel.. Had a 70 Charger come in shop on the 'hook' in the early 70s ,won't start was the complaint on ticket. Mechanic that has the job,tried to start after being lowered off the hook. BLEWEY.
Both V/covers and oil pan came free from their respective bolts.( Total fuel wash down ) Scary at first,when nobody was found to be hurt. Unbelievable laughter. How did we live to be this old?

 

[Erik Morris]

Most times water does NOT burn. Gasoline does, car sitting years look for fuel pump leaking. Most likely cause and effect.

Old fuel pump was removed before I attempted to start it the first time, replaced with a brand new unit.

 

[gdrill]

Do you have an intake valve stuck open? Bent /seized / gummed / burnt

too late on the reply!

 

[Erik Morris]

I blew out the valley pan and the valve covers from a hole in the piston. Sounded like a grenade! do a compression test. If theres a hole you will know right away. Maybe from sitting gas leaked into the pan? PS your rocker shafts are on upside down.

Might be part of the reason I got the motor so cheap. Also, no compression on #5. Pulling motor tomorrow.

 

[Erik Morris]

Do you have an intake valve stuck open? Bent /seized / gummed

too late on the reply!

Haven't gotten that far into the motor yet, but cylinder 5 is a no compression "I'm screwed" party. What I found interesting was that cylinder 5 is the issue, but cylinder 4 or 6 appears to be where the issue manifested its anger.

 

[OKDart]

I'm surprised you had 30 psi oil pressure with the rocker shaft upside down, that's a lot of open area for pressure to be lost.

 

[lemondana]

Back in my younger days I purchased a 73 New Yorker Brougham, 2 dr. Beautiful car, wish I had it yet today. The 440 was gone and the owner had installed a 383 2 bbl. It wasn't completely hooked up. He had told me it could have a hole in a piston. Before I pulled the 383-I thought what the heck? I hooked everything up, not even thinking of a hole in a piston. I gave it a BIG shot of either-BIG explosion. It blew all of the gaskets out bulged the valve covers, oil pan, the valley pan under the intake, and timing cover. I said-Damn, I guess it does have a hole in a piston. Lesson learned!

 

[33 IMP]

If you haven't already, pull the drivers side valve cover, and take a look.

 

[MoparLeo]

Bottom line is regardless of what you may or may not have replaced, fuel got ignited in the engine. Period. Your job is to find out why it happened and where it came from. We are not there to look, you are.
Smart to be removing engine, who knows what other surprises are in that motor.

 

[joe smith]

Have you pulled the dipstick and smelled your NEW oil??? If it smells like gas, quack quack

 

[bm02tj]

I'm surprised you had 30 psi oil pressure with the rocker shaft upside down, that's a lot of open area for pressure to be lost.

Oil flow is controlled at cam bearing so not open to drop pressure