401 Valve cover 'detonation'

icemanii

Have a 401 in my CJ7. On Sat. we went wheeling for about 2 hours when we stopped for a trail repair on another rig. Upon restarting the engine, heard a loud bang, and the oil breather blew off the engine. Also blew out the valve cover gaskets on both sides. Repaired the covers and installed new gaskets on the trail. Engine started up fine and ran perfect for another 4+ hours of wheeling. Started again at home on Monday. My question is, what kind of damage may have been caused by this detonation. And what would have caused it in the first place? Thanks

fifesjeep

I honestly don't think too much damage happened, you probably seen the worst of it... what carb are you running? Can you give us a brief about the engine (is it stock/mods etc)... Have you check your valve train... Do you have any unusual noises etc..

Mudrat

I can't think of anything that would cause that if the breather were working properly??

tufcj

Bad fuel pump or WAY rich mixture putting fuel in the crankcase. Enough heat or a spark, and you have a crankcase explosion. Check that the oil level isn't rising, and smell the oil for a gas smell. I've seen a crankcase explosion blow the manifold off and engine. Bob tufcj

icemanii

fifesjeep wrote
I honestly don't think too much damage happened, you probably seen the worst of it... what carb are you running?
Can you give us a brief about the engine (is it stock/mods etc)...
Have you check your valve train... Do you have any unusual noises etc..

401 with mild cam (unsure of cam as PO installed engine) Roller Rockers, everything under the covers appears normal. No unusual noises. Truck Avenger carb (Holley) with stock air cleaner. Running stock exhaust manifolds as well.

Mudrat wrote
I can't think of anything that would cause that if the breather were working properly??

Appears to be working fine.

tufcj wrote
Bad fuel pump or WAY rich mixture putting fuel in the crankcase. Enough heat or a spark, and you have a crankcase explosion. Check that the oil level isn't rising, and smell the oil for a gas smell. I've seen a crankcase explosion blow the manifold off and engine.

Bob
tufcj

Oil level and pressure are normal, no change from before detonation. No gas smell detected in the oil.