AC Oil Filter Problem on a '49

[Jay Friedman]

I have had a strange problem.  I had been using ordinary 10W-30 in my '49 and was concerned about the low level of ZDDP (zinc) in that oil and the negative effect this would possibly have on the flat tappet camshaft.  I read on this forum that a good oil to resolve this problem was Brad Penn "Penn Grade" 30 weight oil which has a high ZDDP content. 

Bought a case of this oil and changed the old oil for the Brad Penn oil.  Even though it's 30 weight, it seems very "sticky" compared to ordinary oil.  With the Brad Penn oil the engine runs fine with normal oil pressure, but oil began immediately leaking out of the cover gasket of my AC oil filter.  Thinking the gasket was faulty, I installed a second cover gasket from a 2nd new oil filter cartridge box and had the same results.  Since I have to drive the car to a club outing, I removed the oil filter assembly from the motor and installed plugs in both holes in the block.  I then checked the filter cannister for cracks and the filter cover for flaws and found none.  Now there are no leaks but I'm perplexed as to the cause, since the only variable I'm aware of is the different oil.  Does anyone have any ideas?

[Jay Friedman]

Art, thanks very much for the photos and the thoughts (out loud are the best).  I can easily see in the photos that the AC P115 and Napa 1100 have much thicker gaskets than the Hastings.  (I also have both a brand new Napa and a couple of NOS AC P115s I bought at Hershey among my stuff.)

More details.  The first filter cartidge and gasket I installed was a Fram C-21 (equivalent to AC P115), which is also an "old" style with a thick gasket.  Feeling a bit paranoid, I thought the problem was maybe that they were Fram and not AC, and, more seriously, that there was an unseen flaw in the gasket.  So, even though I had successfully used Fram filters in the past, I changed both the cartridge and the gasket for an AC P115 cartridge and gasket.  I still had the leaks and could only mutter to myself "What the ---- is going on"?  (Didn't say "heck".) 

[Roger Zimmermann]

Jay, you changed two parameters when you switched for a different oil: the oil itself and a new oil filter/gasket. You installed another filter after the first one leaked, still have the same problem. What's about the oil? you wrote yourself that it's not as fluid as other oils. Could it be the wrong oil in the cans?
Another possibility: during the oil change, the return line was blocked by dirt (it would surprised me...). You could also measure the oil pressure at the outlet to the oil filter, it should be the same as the main oil pressure.

It seems that when the engine is well broken in, the high content of ZDDP is not needed; can somebody confirm it?

[Jay Friedman]

Art, Roger,

Thanks again for your replies. 

I've checked the top of the cannister and the cover with a straight edge and both seem to be straight. 

The rubber washer on top of the cover is very worn.  I hadn't thought about that, Art.  Will try and find a new one tomorrow at a hardware store. 

Also, I do have an NOS top I found some years ago and to be absolutely sure will use it when I re-install the filter assembly.  Will let you know how it turns out.