I have an early 21 stud flathead in my 35 Cabriolet and up to now the car has leaked only a very small amount of oil, a couple of drips in 2 months on my garage floor. I drove it some yesterday morning and about an hour after I returned home I noticed a big drop of oil every foot on my driveway. Peered under the car and in that hour I had a circle of oil about 10inches in diameter on the floor. It appears to be coming from the hole in the back of the pan under the flywheel (weep hole) which would indicate a probable rear main leak. With it becoming so bad so quick, does that mean the babbit let loose or cracked? Any other thoughts? I am new to flatheads, I am hoping there is an easy answer.
You are probably right that this is a main leak, but first before you dive in SMELL the goo. Engine oil is pretty innocuous, transmission goo smells like some left a dead whale out of the freezer too long.
Next...***uming it isn't 140 weigh whale oil... Scrutiny should go to rear main drain system and rear main clearance. You should have a slinger, circular blade or rid that throws off stray oil into a groove. Drains out of the groove have to be open, of course, and I think these engine have a drain tube going down into oil. If that tube is gone or is too short, the surface thrashing of the oil caused by windage can in effect pump oil up tube or at least discourage oil from exiting, with obvious consequences. Oil has to clear efficiently from the drain groove since only alternatives are the pressurized area in front or the easy way, out the back...which it will choose, of course. Clearance has to be reasonable, of course...the old NAPA '32-36 book suggests a quick and dirty check short of tearing down far enough for real measuring: put a short strip of .005 br*** shim, 1/2" wide and length of the journal, on the bearing material and turn crank. If you can turn it you are well past factory spec and you will be paying the next installment of sending your paleomachinest's kids through college...
My flattie (driven about 100 mies a weekend) will leak about a 50 cent size spot week to week. I drive it fairly hard usually about 70 MPH. Sooo they don't have to leak bunches...
Funny I still use bio ... animal fat oil in my flat trans and diff. Good for yellow metals. Hard to find but available. If your fussed to find it go to a large oil depot that supplies cyclinder oil for large compressors. Not nessesary by any means.
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