HC head increasing oil leak?

German guy

German guy

Senior Member
My 30 Tudor has always dripped a bit engine oil...not much....maybe a drop every day or two and no obvious source is apparent. I installed a 6:1 head and it now leaks a LOT more. It seems that a fine mist of oil is coating the bottom of the oil pan as well as the underside of the transmission and eventually amounts to enough to drip. After a few days of standing cold the dripping is much less....almost stops Seems that heating up and thinning the oil when driving increases the mist and dripping. Can the increased compression exacerbate a slow leak at the oil pan seal? I inherited the car with an already rebuilt engine and it looks like silicon was used in lieu of gaskets across the board..including the oil pan....thin bead of red silicon around the joining edges at the pan and block. That bead is always slightly damp with oil...never enough to cause a noticeable drip, but you can always wipe a bit of oil off. Could increased compression force more oil out of that bead?
 
Maybe the vented oil filler cap is clogged and isn't venting the crankcase? Can you wash it out with solvent or see that the pipe is empty? I think I have heard of people putting mesh in the pipe to keep oil droplets from the cap.
 
Bruce has a good suggestion. If the engine has some blowby the increased compression will increase that and thus increase the pressure in the crankcase. If the breather and cap are restricting the venting then, yes, the higher compression head can increase oil leaking.

You could consider fixing the leaks too.
 
The real test is leak down
This will help diagnose where the leakage is originating

The other question is are you driving it harder and exposing a weakness?

J
 
Clearly combustion gas getting into crankcase, blowby. If it is a rebuilt engine with not a lot of miles it may be that the rings are not fully seated.
 
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