620 air noise from valve cover ?

dmiller · Oct 21, 2017

620 making an air noise, appears to be coming from a leak in the valve cover? Sounds just like my A used to when I left the pet cocks open. Seems like an odd noise for a valve cover leak, seems odd that there is compression there? I know it needs a valve cover, but can't really explain the air noise (you can put your hand up there and feel it too).

Ideas?

DrCharles · Oct 21, 2017

Bent or burnt valve (compression coming back up the valve stem into the cover)?
Crack in the head?

620 John · Oct 21, 2017

Are you sure it's not an exhaust leak?

Do you feel any air out the breather tube?

If it's building that much pressure in valve cover there must be severe blow-by.

dmiller · Oct 22, 2017

Yes, it is old and worn. The breather has constant smoke out of it, looks darker than the exhaust.

Mike M · Oct 22, 2017

Sounds like way too much blow by. Those series have thin rings and I have seen several with broken top piston rings. But usually by the time it takes to do this the cyl. bores are worn enough they need rebored anyhow.

620 air noise from valve cover ?

dmiller

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DrCharles

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620 John

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dmiller

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Mike M

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