early 50's cub...too much oil pressure

The relief valve has been checked, cleaned and finally even replaced (both piston and spring). It seemed the obvious culprit, but the problem remained exactly the same.

What about fuel leaking into the cylinder due to a stuck carb float, etc. while it's not running? Is it feasible that it could leak enough fuel down past the pistons into the crankcase, creating too much volume, which returns to normal after leaking a bit?

What else could cause this? Any theories are greatly appreciated. Any similar experiences are even better! Thanks in advance!

Thanks for the replies so far. It is the FILTER cap that has a small crack. I'm pretty sure the pressure really is too high, because the gauge pegs out for a while after starting, then later falls back to the normal range. I guess it's possible the gauge is faulty, but it reads normal after the leaking stops.

Yeah, the gasket is being replaced with the filters. We've picked an independent mechanic's brain and a shop manager at our local IH dealer, and the relief valve was the only theory they had.

Thanks again, and I'll post anything I discover and/or try.

Mark

I actually read the query both ways. My thought is that if the oil filter cap were cracked and leaking when the engine was cold, when the oil warmed, the crack should open wider and more oil leak out. May be not strange things happen.

*the cap itself...if it's not fitting square on the filter housing, THAT'S definitely a problem. If it's the problem, don't play games; replace it.

*the oil filter housing gasket UNDER the cap...you ARE replacing that EVERY TIME you change the filter, aren't you? And making sure you get every trace of theold gasket removed?

*the sealing ring between the bolt in the filter housing cap and the cap itself...original was a copper crush-type seal ring, and those are MEANT to be changed every time you remove the cap.

If the problem IS the filler cap instead of the filter cap, these other folks pretty much have your problem covered.

You don't have too much pressure; you just have an old fashioned oil leak at that cap.

Allan

I suspect the cause of the oil leaking out of the crack in the oil filler cap is splash from moving internal engine parts. I get a bit of an oil leak out of the filler cap/dip stick on my Cub when the engine is cold. Quits shortly after starting the engine.

JB weld on the crack.

As long as the oil pressure is in the normal range when the engine is warmed up - I wouldn't worry about it.