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Got the truck home last Monday. Truck was hooked from the rear. I wanted the truck backed-in,since I'll be working on the engine SOON! We decided that it wouldn't do any harm,starting the truck just long enough to back it in. I started it up,and the two tow operators,checked for leaks,(one on each side). Surprisingly enough,it didn't leak a drop! This makes me believe that the leak was caused by excessive pressure built up in the crankcase. I know I need to check the breather tube assembly. Are there other problem areas that would cause excessive crankcase pressure? If that aforementioned plug fell out behind the cam,wouldn't that leak show up,while I was backing the truck in? I had it running for at least two minutes,and oil pressure was 60-plus #. Any way of checking(the oil plug),without removing the bell housing? Can you access it,if the inspection cover is removed? Sorry,I don't have a garage. Everything is done outdoors,so I'm trying NOT to pull the engine. Any advice is GREATLY APPRECIATED!! THANKS!!

The bellhousing covers most of the cam plug so I don't think it could have moved.
A 235/261 needs to be vented at the valve cover and a clear road draft tube.

Thanks,Dave!!I'll be sure to check both areas. Since I lost about 2 quarts of oil,(within a span of three miles),I'm thinking something must've blown. I'll do the drill in the dizzy procedure, and see where the leak is,for sure. The hydrovac works well,so I don't think the valve in that line is faulty. I'll check it anyway,just to be sure.
(QUOTE:)"The bellhousing covers most of the cam plug so I don't think it could have moved". Is this plug pressed-in,or "threaded"? Could it work itself loose,especially under-pressure? Do I need to pull the engine in order to repair correctly? THANKS!!

If you lost that much oil externally, there should be a really big mess somewhere underneath.

Unhook the oil pressure line at the block. Add a air line fitting and fill the system with 60 to 70 psi air to see where it comes out at. If the breather system is working, you will hear it at the draft tube or valve cover. If they are plugged, go to the bell housing area or front seal area, the air will get out some how.

Joe

Great idea,Joe!! THANKS!! Truckernix,There WAS a BIG MESS,when I pulled over,and oil was dumping out of the rear main area,between the pan and bell housing. Now,after running for a couple of minutes,with 60-plus pounds of pressure,there wasn't a drop. Oil was topped-off,before starting. After sitting for three days,not a drop on the ground,under the truck,either. I know these are great engines,but this thing couldn't heal itself:)! I know that I have a major concern somewhere,even when I find/clear the vent restriction.

On my 216 the rear seal doesn't start to leak until the engine has warmed up a bit, then it leaks more at idle than at higher rpm. It'll continue to drip some after shutdown also.
My rear seal leak avg's around 1 qt every 200-250 miles.

Is it possible you had the oil level overfilled initially?

Using a mirror and light, checkout the valve cover to head gasket mateing area's at the back of the head between the cover and firewall. That's the lowest spot for return oil and sometimes the oil can build up there and find it's way out via a bad gasket seal. My 216 seeps back in that area after a good hard run.

Also check the side cover rear bottom corner where it mates to the block. If that gasket has a leak you'll have a pretty good stream of return oil from the head to the oil pan.

Once oil warms up and thins out it'll seep out in all kinds of places.

You also mentioned your draft tube may be clogged and could be causing the bottom end not to vent. That's a good possibility and easy enough to check. I've seen engines spew oil all over the place from all sorts of sources when someone has buggered up it's venting system. An engine's got to breath!
The draft tube is pressed in so you'll have to knock it up to get it out of the block. Be careful as it's easy to deform it. You could try to blow compressed air back up through it, you should hear air hitting the oil plus escapeing out the valve cover up top.

Good luck
Dave

If the rear "U" part of the Pan Gasket is fallen out, it can leak pretty bad from back there, and or look about like a Rear Main Seal leak.

Had you had the pan off before this leak got going?

Thanks,Guys!! ALL GREAT ideas,and will be checking all for problems! I'll post results in the next couple of days,or so. THANKS,AGAIN!!