So far I have zero sign of any water intrusion, corrosion or significant wear on this engine (looks to be a later model replacement block) so things are going well, just want to be sure I’m not making any mistakes. I’ve been around old poorly maintained junk all my life on small farms, but I can’t say I’ve ever fired an engine that sat idle for 40 years before so it’s a new experience for me

They should be fine, the last time the engine was shut down, the oil should have drained back into the sump/oil pan. This should have happened within the first month or so.

I have had very good luck getting non-preserved engines that sat for decades going by, cleaning out the oil sump/pan,  changing the oil filter & oil, filing the points, & rebuilding the carburetor.

Of course, YMMV.

Keep up with the picture taking, we love pictures. (Says the guy who has never learned how to post pictures.)

It’s nasty and jell-o like but it’s not solid enough that I have large concern that it could plug a passageway or starve a bearing if a small amount was still present on startup. Still going to clean it the best I can within reason.

Good plan.

Thanks for the update.

Someone brought over a 1992 Cherokee with the in-line six for me to look at. This was in 1994 so the Jeep was only 2 years old at the time, but she said it was "using a lot of oil". 

First thing I noticed was absolutely no oil showed on the dip stick, next thing I noticed was the box for the air cleaner was completely full of very black dirty oil. Next thing I noticed were a pile of empty oil bottles which were one of the cheap brands of "recycled" engine oil sold at truck stops and some of the convenience stores of the time, basically a mixture of used oil they ran through some filtering. 

There were two design problems with both the in-line six and the four cylinder engines used in those Jeeps. I had encountered the oil in the air box a year before on a 89 Comanche Pickup with the four cylinder engine. 

The crank case ventilation system was a small tube running from the a small orifice fitting on the back end of the valve cover to the manifold. There was a larger tube running to the air box. The oil return ports in the head were also too small.

The system works fine with proper maintenance, but this poor Jeep had been terribly abused. She had ran it hard with cheap, dirty oil long enough that the small orifice vent became clogged, the oil return passages were clogged, and the combination of these two things caused the oil to pool in the valve cover to then be siphoned into the air box through the breather tube. 

I suppose the oil starved engine created enough heat to cook that sludge in the valve cover, because it was hard enough it had to be dug out. 

 

After all this cleaning and the oil draining into the pan 40 years ago,  pressuring the oil through the engine might be a good thing.  When I picked up my F head after rebuild the foreman loaned me an oiling  cylinder.  Pour in a couple of qts. put the lid on pressure up with air, hook it to the block at the oil pressure tap, open the valve and oil goes to the bearings.  Every thing gets preoiled.   Seamed to work good for my engine.

Turning the oil pump to bring up the oil pressure with out the dizzy installed could work too.

Lots of ways to attack this.