Rear Main Leak??

Chris Nelson

Chris Nelson

Senior Member
I have a 59AB with 8BA crank and rods in it. It has not leaked in the first 3,000 miles of driving, but now after a 300 mile drive, I notice I am down a 1/2 pint or so on the dip stick and I have a small puddle under the rear of the engine. I know, they are just marking their territory. I am running 10-30 synthetic oil, but I doubt that it is of any significance. My question is; do I have to pull the engine to fix this? Is this a rear main sealing problem? What are my options?
 
from my experience sythetic oil tends to leak/burn out of old Ford more than conventional oils. Clearences are not as tight as modern cars. In my two flatheads (40 and a 51) I run 20w50 Kendal oil and it does not leak or burn off as the synthetics I tried. If it is not dripping a little-you are out of oil!
 
If you have an 8BA crank in a 59ab what distributor do you have?? 1/2 pint in 300 miles is not much. As mentiond above, go to 20/50 oil.
John
 
you can not break in an eng with sytc, oil you schould run reg oil. after break in you can wast your money on syntc. unless your runing a raceing eng any good oil is fine for a street eng & cost a lot less
 
The engine was broken in with SAE 30 non detergent for the first 1,000 to 1,200 miles. I then switched to 10W30 synthetic. My other flathead 8BA has been running synthetic 10W30 for 8 years and not a drip or drop. This one runs with 50 lbs pressure at driving speed and about 10 lbs at idle when warm. It didn't start to drip till I ran it about 300 miles in one day. Before that it was dry underneath for about 2,500 to 2,700 miles. I don't know what I could have done to cause this to start now. I can't believe that a 300 mile trip in one day would cause anything. It maintains a steady 180 degree temp all day.
 
What kind of crankcase ventilation system are you using? If it gets clogged or gummed up, you could be developing pressure in the system. Also overfilling the crankcase can cause it to leak.
 
Oldford2 asked what distributor I'm using. It is set up as an 8BA with a Mallory electronic ignition. Fires up on the first rev. and runs smooth. even with the 77-B cam and dual carbs
Flatjack9 asked about the ventilation system. I am running a PCV valve on both of my flatheads mounted in the hole for the "Road Draft Pipe" in an 8BA manifold and connected directly to manifold vacuum. The PCV valve is a BW #382, which is closed at 16 to 18 inches, floats at 8 to 10 inches and is open at 1 to 6 inches. The oil fill uses a filter type filler cap, so no blow by or pressure build up at all. The crankcase pan vent is blocked to prevent any dirt input to the crankcase due to the PCV pulling through it.
This problem just developed after 2700 miles with no leaks. All your thoughts are helpful. I just hate oil on the floor of the garage.
 
The 8BA and 59A have differences in the rear main area with concern to sealing. The cranks are close enough that a change to a Merc crank would not effectively change the sealing characteristics but it doesn't change the way a 59A seals up by comparison to the 8BA. You will have to find out if it is leaking from the rope seal in the cap or the pan seal area. Some rope seal material is better than others so that can have an effect too.

I work with synthetic oils in the aviation business. If there is a way that the synthetic stuff can find its way out, it will, and it will do it long before the mineral stuff finds its way out of there. I'm not questioning the synthetic stuffs capability to lubricate but am pointing out the one drawback to its use. Oil level in the pan can also have an effect and 59A engines differ from 8BA engines in this respect as well
 
Thanks all. those are good points to ponder. I guess the change to non-synthetic would be a good first try. Also the easiest. I appreciate all the ideaas that are posed. A couple that I had never heard of. Unfortunately the rope seal retainer in a 59AB can't be spun out like an 8BA. Darn. Maybe I need to get used to having a drip pan under it. I guess there are worse things to get used to.
 
Buy a silver tea tray to place under the rear seal. It adds a little class to the whole experience. Also double check that it is not leaking somewhere else and being blown to the rear at speed.
 
Woodypecker, that was a great idea. Silver Tea Service. Now where am I going to hide when my wife can't find her tea service. I did a thorough wipe of the whole engine to see if it came from anywhere other than the rear main. Clean as can be everywhere except at the drip hole of the pan.
 
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