Need help/question - 327 road draft pcv question?

[burningsquirrels]

Hey folks, some back story first. So I have a well-running, relatively new-to-me 67 C20 with a 327 and 4 speed. I was running a bunch of errands one day and put close to a couple hundred miles on it one day and noticed it could barely hold an idle towards the end of the day. After some troubleshooting I found that it had the symptoms of a vacuum leak. Cover the carb, and idle shoots up. I checked all the hoses and timing, the timing was pretty far off. The hoses... The road draft tube went straight to the large manifold port on the carburetor with no PCV valve - I guess that was the vacuum leak!

After reading some threads on herere, I decided that I was going to try and seal up the 'hat' in the back of the engine block. I started by putting a vacuum cap on the tube that leaves the hat. I then took the hose from the manifold vacuum port on the carburetor and ran it over to a PCV valve that sits on one of the breather holes for the valve cover (the breather on the driver's side is still there). That, combined with the timing adjustment, I was able to adjust the idle speed screw down a bunch. I guess it was set very high because of the original issue. Now the motor runs great and better than ever!

Problem: It now pukes oil out the back of the motor and has a James Bond quality smokescreen wherever I go! When I say oil, it's leaking from somewhere and I guess it's burning off the headers. It's all underhood. With regards to puking oil - it's somewhere from the back of the engine. I hosed it off (just the back, of course, away from the top end) to clean off any oil and went for a drive. Did a lap, and it started smoking again. I parked and checked the various places from the back using a clean white paper towel to look for oil traces. Didn't seem to be a rear main seal, or the valve covers. The distributor and back of the intake manifold looked okay. It seems like it may all be coming from the 'hat' thing on the back of the motor. I took it off, cleaned the hat and the hole, and tried using ultra black over there as I couldn't find a gasket online, and I didn't have any o-rings big enough. That didn't seem to help as after a test run a couple days later, it was soaked in oil again.

So I guess my question is, how is that 'hat' thing supposed to seal against the block from the factory? When I removed it there was no trace of a gasket, and I don't recall seeing an indented ring for an o-ring on it? I saw a thread that mentioned a block plug but haven't found anything smaller than a complete kit. What do you folks suggest?

Thanks!