My Willys 3A and 3B Community
TECH FAQ SECTIONS => Engine compartment => Topic started by: Phil on March 06, 2024, 12:14:14 PM
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Rebuilt 1953 F head engine. It didn't need to be bored so the cylinders were just honed with new OEM piston rings I bought from Kaiser-Willys Jeep, they were still coated in cosmoline. Engine start right up but after a minute it starts to run very rough. I can't get the oil to stop leaking out of the gasket of the intake valve cover so I assumed it might be a PCV issue but it's all new and working right. Pulled the head and there is oil on top of all the pistons and that is fouling the plugs. Before I pulled the head I did a compression check and it showed between 70-80psi. My manual only says all the pistons should be within 10% of each other which they are but I have read elsewhere that anything less than 130psi indicates excessive blow back and wore or bad pistons. I guess worn intake valve guides also be an issue but I can't see all of them being bad. Thanks
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Phil,
Sorry, I've been real busy lately and noticed no one has jumped in yet with opinions. Before you dig into the valves, I'd suggest a simpler direction first.
You stated newly rebuilt (at least the rings) so it hasn't been broken in yet. Seating the rings will help with excessive oil like you found.
120-130 psi is the correct compression but I can't imagine you'd see that on an engine with new rings. I also see the "within 10%" in my manual too, but that relates to rebuilding and using the crank 4 times per cylinder method (para E-106A). Use that guidance to differentiate between leaking rings or valves. I want to guess the test will show rings as yours are new.
The PCV system shouldn't cause any oil build up in the combustion chamber.
Also, a gasket shouldn't leak if it's sealing (good contact and correct torque). You can sometimes tell upon removing and inspecting a leakage from oil passages into the combustion chamber.
Have you found out anything else so far?
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If the ring gaps are offset like they're supposed to be there should not be any oil in the cylinder.