I have a recently rebuilt 400 in my 68 Cutlass ( less than 500 miles ) that just doesn't seem to be running as good as I think it should. One thing that bothers me is the amount of moisture building up on the bottom of the oil fill cap and inside the breather cap on the valve cover. I changed the pcv thinking that might help, but it hasn't. last night after about a 20 mile run, I checked the oil cap with the car running and again found water drops and some milky oil. With the cap off, I removed the pcv and noticed a lot of blow by coming out the oil fill tube. With the pvc in place, it quits. another thing I noticed was after a fairly hard run, it will blow oil out the dipstick tube.
Any ideas ???

 

This just does not sound good at all.
There is moisture (water) getting in there from somewhere.
Any "milk" of any sort is screaming at you to NOT drive this car, and get it repaired.
Get some experienced help IMMEDIATELY, somehow, something is not sealed, or you may have a comprimised (cracked) part.

The water is coming from somewhere, do NOT dick around with this.
That is my opinion.
Jim

 

The milky stuff on the oil cap is usually caused from short trip driving and is usually nothing to worry about, but it still sounds like something is wrong with your engine. Connect a vacuum gauge and see what the engine has. Might also be a good idea to do a compression test.

 

Does it have a after market aluminum intake on it? Most leaks come from these if you used the stock turkey tray gaskets instead of after market composite gaskets......A few more engine specs maybe...your getting some water or moisture in the oil somewere that needs to be addressed........soon......

 

Sounds to me like you have a blown head gasket causing water and compression to get into the engine internals or a cracked head maybe. Stop running the engine until you correctly identify the problem.