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MCM 170 Pressure in Valve Cover

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cbvus2k

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"I have a 1986 MCM 170... just

"I have a 1986 MCM 170... just replaced head gasket, intake and exhaust mainfold gaskets and elbow gasket. Replaced spark plug wires, spark plugs, etc. She will start right up but there is excess pressure coming out of the vent in the back of the valve cover. If I remove the oil fill plug, the engine will rev up. The head and valves were clean as a pin. Slight carbon deposits on the top of the pistons. No sign of oil on the top side of the pistons. Is it possible that the exhaust mainfold is leaking back into the head in some way? I really need some expert advice! Thank you in advance for your reply."
 
check your pcv as well. not mu

check your pcv as well. not much causes that kind of blow by but rings. Follow mr stephens' advice.
 
Thanks to all for your respons

Thanks to all for your response. I plan to do more work and testing on my Sea Ray over the weekend. I'll let you know how it turns out!
 
"Michael;
There is a kit you

"Michael;
There is a kit you can get at Autozone or anywhere that enables you to apply air pressure inside a cylinder thru the spark plug hole for the purpose of changing valve springs, seals, keepers, etc; without having to pull the heads. Putting pressure in each cylinder this way would quickly show you if blowby is the problem. You will hear strong hissing in the valve cover breather, plus noticable air flow.
Just a thought,
Rod"
 
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