HD 213 engine oil leak

Following an overhaul,the rear seal on my 1936 C-15 developed a severe oil leak after about 3 hours running time. The engine is an HD 213 and has the same rope seal as the GRD engines. The oil leak is a steady stream of oil--not a drip. I have removed the engine and see no obvious reason for the leak. The flange or ring on the crankshaft only presses into the rope packing about 1/16 inch. I thought this may not be enough, so purchased a new rope seal from a different supplier expecting to see a larger diameter rope, but it is the same. Is this all the flange should press into the rope seal?? Also the oil drain hole at the bottom of the groove was partly or completely blocked by the rope seal. Could this be the problem?? Your help would be appreciated as I do not want to pull this engine again!
Thanks,
Dave

It's weird that the huge gusher started AFTER 3 hours of running. However, even if you installed the rope seal blindfolded I can't figure the gusher.
Maybe a drip drip but not a gusher.
1/16th of an inch seems like not enough. My experience with rope seals is that the crank journal squashes the seal down pretty good. 1/16 only comes out to .0625". About twice and old plug gap.
The steady stream of oil leaking at idle suggests a large portion of lubricating oil on that rear bearing is exiting through the rear seal. This means mondo hole somewhere in that seal?
It's been a while since I had a flywheel off of one of these. Do the flywheel bolt holes go into the crank oil galley or do they exit inside the engine's crankcase?.
Is it possible that a rear oil galley plug behind the flywheel was left loose?
I can tell you from decades of tracking down oil leaks that a slooow approach questioning everything at every stage is the only way to proceed. My techs will tear something apart in a frenzy, diagnose oil leak source in their heads only to have to pull the whole works apart again. And again.
Then the greybeard (me) will walk up with a LED flashlight and start asking questions.
Anyway, someone here with recent experience will chime in.

The flywheel bolts onto a flange on the end of the crankshaft outside of the crankcase. The only other source for a leak behind the flywheel is the cap at the end of the camshaft. I agree that with a steady stream of oil leaking that there it oil pump pressure.

So I'm guessing it's dry at the cam?
We often use a dye in the oil when we're getting our butts really kicked. Sometimes the local parts guys don't know what I'm talking about but I usually find some.
In your case you'd have to pressurize the oil system with engine out. Can you do that? Does the dist have the drive gear or does the oil pump?
Could you pressurize it while another pair of eyes look at rear seal area?
Just trying to think outside the box so you don't have to pull engine again.

Not being a smart aleck--you have something like 30 weight oil in it?
Synthetic oil will find every open pore on an old engine...

It has 30 weight oil in it. I like your idea of pressuring the oil system. It is a gear driven pump off the camshaft, but I have a spare pump with the drive gear removed that I use for prelubing engines. I can swap pumps and try it!
Thanks,
Dave

Following an overhaul,the rear seal on my 1936 C-15 developed a severe oil leak after about 3 hours running time. The engine is an HD 213 and has the same rope seal as the GRD engines. The oil leak is a steady stream of oil--not a drip. I have removed the engine and see no obvious reason for the leak. The flange or ring on the crankshaft only presses into the rope packing about 1/16 inch. I thought this may not be enough, so purchased a new rope seal from a different supplier expecting to see a larger diameter rope, but it is the same. Is this all the flange should press into the rope seal?? Also the oil drain hole at the bottom of the groove was partly or completely blocked by the rope seal. Could this be the problem?? Your help would be appreciated as I do not want to pull this engine again!
Thanks,
Dave

Dave

Your description doesn't make sense "The flange or ring on the crankshaft only presses into the rope packing about 1/16 inch" nearly all engines I have ever pulled apart have the rope/cork seals pushed into a groove in the cap and then the seal runs direct onto a flat surface on the crankshaft. when you fit them up you need to leave the a little higher than the housing so when they clamp down they are tight.

Some early engine like my CT Lycoming never had a seal they just ran a oil slinger and drain tube. like this