Hello, friends.

I have one of the rare ALUMINUM 225 Slant 6 engines in a 1961 Plymouth Belvedere. I am having an issue where the oil is building up and blowing out under pressure around the filter seal. The pump will then pump nearly ALL oil out of the engine once the rupture is established. This is an engine that hasn't been started in awhile but all of the seals and block are solid and intact. ANY IDEAS???

Usually leaks at a spin-on oil filters are due to the old gasket sticking to the oil pump. The two gaskets don't seal to each other and there is a big leak. Take the oil filter off and make sure you only have one gasket and that it's on the filter.

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Joshua

If the engine has sat for a long period, the oil pump's pressure releif valve could be stuck closed.
Pull out and service the relief valve per the FSM.
DD

Could also be a damaged and leaking oil pressure sender.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I agree with both Doc and Dan, I had a sending unit really leak bad because of a pressure release valve plunger, beeing stuck,Guzzi Mark