OK, I found the leak.  It was a brass compression elbow for the oil pressure on the front, right side of the block,.....I know that it is not a stock piece, but I used it to more efficiently route my oil line to the gauge.  I have a braided steel hose hooked up to it.  I started to look down from the top front of the block.  As soon as I moved the brass compression elbow ever so slightly it started leaking.  That explains why it was so intermittent.  I took the elbow out and hooked the braided line straight up to the block.  No leak.  Now I have to figure out how to tune down the oil pressure with the little chrome knob on the adjuster.  Thanks to all.  Looks like I don't have to pull the motor.  

Dogscarf

With a leak as bad as you describe, consider the following method.

Go the the local parts store and ask for UV dye for the engine oil.  Go to the home center and buy a "black light" bulb as a UV source.  Degrease the engine to remove all the old oil.  Do not run the engine.  After dark, add the dye to the oil, turn on the UV light, and turn off all other lights in the area.  Now run the engine while shining the black light on the front of the block and transmission.  With a leak as bad as you describe the source of the leak should appear quickly.  If it doesn't show up immediately, the leak may be from an "internal" source like the primary seal.

I'd be cleaning off the oil transfer pipe banjo fitting, the oil pressure relief bung, and the oil pressure sender/pipeworkand having a very careful watch of where the oil is coming from.  It ought to be very clear with the grille off.

There is really to much stuff in the way to get a good look.  It for absolute sure does not come from the pressure relief valve.  I put another one in there that is adjustable and there is no leak there.  It is not running down the block face.  I need to start it again just to watch it leak.  I may be mistaken from what I said in my last post, it doesn't leak when sitting, but the leaks were from cranking it over prior to starting.  It leaks like the Exxon Valdez when running.
Dogscarf

This would appear to be a very strange oil leak? are you sure it's not coming from above this point and running down the block face and accumulating on the through bolt making it look like the leak is at the bolt? I'd think it more likely coming from the oil pressure relief cap or the transfer pipe above it and running down the block? If it was leaking between the engine/transmission face gasket I don't think it would be that bad of a leak?

The leak appears to be all of the time, not just when the car starts.  Of course, it is much more pronounced when running, like 100 times. A drop every second.  It even appears to be coming out at the top of the 5/16 bolt which is located upside down with the threads just barely at the bottom of the block.  That to me seems to indicate a problem with the oil galley.  The engine and gearbox have been together before and did not leak.

I will try to take a pic.

Dogscarf 

Does it leak all the time, or only during/after running ?

If it's all the time, then the lower location dowel may be holding the transfer housing off the gearbox a smidge.
If it's only during running, then it's the primary gear oil seal.  Losing the seal doesn't guarantee clutch slip, especially if you've fitted one of the red plastic oil flingers behind the flywheel.

Tell you what, jack the car up and look underneath the clutch cover, you will see a hole that is about a size of a corn. IF you see oil that's coming out of it, then BINGO!! your Primary gear seal is Shot!......if you can't live with the oil leak, then replace it.....i've lived with it for 2 years, no biggie!...at least i know i am driving a true blue British car. I see evidence all over my garage and wherever i park.

CAUTION: when you jack the car up, be sure to put the jack stand on the proper jacking points NOT on the lower side panel.

I think that Mur may be onto something.  I did not drill out any plugs however.  I think because this is such a massive oil drippage/leak that it must be the way the oil is draining back into the gearbox.  I wonder is sealant or part of the paper gasket is covering the oil galley hole.  The engine must come back out, that is for sure.  I drove the car yesterday and there was no slippage of the clutch, so it is not the primary seal.  

Dogscarf

Rob.

As usual, you post from an uninformed perspective with no actual experience to draw from. People have asked you time and again to stop. Your contributions have only negative value to this forum.

A leaky primary gear sends oil out the bottom of the clutch housing.

Sir Douglas was right, it's the Primary gear seal that is leaking., it's already worn out. The oil leaks and crawls to the clutch pad and other components  and when the car runs, some of the oil spins all over the cover, that's the reason why you see some oil dripping g from where the location  of the starter is... that was my problem before, my primary oil seal was leaking and the car has eased for a very long time, it has accumulated and deposited around the clutch pad, thus when i drive the car it judders, and it was the main reason why my car needle got bent, and i had to replace it.

i tried using AT205 reseal and the problem went away.  Before i see 3 drops of oil per hour, after using the reseal, i only see 1 drop per hour...try it

I suspect you have some absurd issue with your oil pressure relief valve. Did you drill out and tap and plug the small galleries of the oil pressure relief? Maybe you plugged the drain and left the plug out that then flows oil out between the bottom of the block and the transmission.

Here is a photo of the correctly plugged and correctly open drillings of the bypass circuit.

i use only Toyota FIPG, this is the best i have ever used, 30 plus years of use, good stuff

As you said, the engine needs to come back out.

Look for problems with the primary gear seal (is it in the correct direction and/or is its lip cut or torn).

I cannot speak for what sealants other people use.  I have used Aviation Form-a-Gasket in the past.  On a non-Mini rebuild two years back I used the Permatex version of Hylomar and it worked very well.  I try to limit when and how I use RTV sealants.

Fellow Minioids, Well, as of my last posting I picked up an Aldon yellow distributor and new coil for my Cooper S with a 1275.  Installed and got the engine running right away.

 Now I have a massive oil leak coming from the right-front side of the engine gearbox mating.  Looking straight on at the engine it is below the starter motor at the last bolt before the clutch housing.  My oil pressure is 100psi when the engine is running.  Very high, probably too high.  I wonder if this contributes to the leak.  I have 5/16 bolts between the gearbox casing and engine and all of the holes were chamfered.  I re-tightened all of the bolts.  I get a 6 inch puddle of oil after only 10 minutes of running.  I think that the engine must come back out to undo the gearbox from the engine to replace the seals.  Curious, what do most people use along with the paper gaskets if anything?  Hylomar, black silicone or what?  Maybe the bottom of the block needs to be skimmed as does the gearbox.
I hate to haul the engine back out and waste several more days but that is looking like what I must do.  Thoughts?

Dogscarf

1968 Morris Cooper S