Hello,

Ended up on a BB inspired crusade two years ago that started with an effort to lower the engine block pressure and then fixing the oil leaks. All this started with the same issue you are having now, excess pressure in the block. The only seal that has not been changed is the rear engine seal and there is a tiny leak there, not worked enough nerve yet to replace it. In the process of doing this found things like holes hidden on the bottom side of the large intake hose, rotten vacuum lines, restricted flow in the old breather box, a replacement flametrap to breather box fitting that turned to mush,a new breather box that did not seal properly, clogged vacuum orifice on top side of the intake manifold, and old flat o-rings. It was the result of general lack of attention to maintenance on my part and the age of the parts. Today have a clean belly pan (used to have to scrape oil and steering fluid covered gunk out), a clean To engine, good strong block ventilation and a smooth surge free idle. Used to get a surge at idle sitting at lights (all of a sudden) and that's gone now.

Here is what I learned doing all this,

To pull the breather box off there the two 13mm bolts that hold the breather box on. You can remove the two bolts by feel reaching in around the back side of the throttle body and following the flame trap hose down with your hand. I pull the big hose off and get everything from the air filter to the throttle body out of the way. If you have not recently cleaned the throttle body pull it off also for a even better view. Once you pull the breather box off, you can get a gallon of an oil based solvent and soak it to clean it out or just get a new one. If you reuse the old box, be sure to install a new o-ring. A lot of folks think they did not have one when they first pull the box off (I was one of them). There should be a flattened black o-ring smashed down in the groove around the larger opening (closest to the firewall). Use a dental pick and pop it out, be careful and do not scratch the seal surface of the box. If you soak the box out you will find for the lack of a better description a lot of soot or fine particulate inside. If it is badly clogged you will get quite a bit out. When you install the box back, snap the new o-ring up in the groove and be careful(but not paranoid) when you put in back in. There is a hose on the left hand side (hole closest to the engine front) that you want to line the box up on before pushing the box down onto the engine block. If you push the hose down in the block fixing it involves pulling the oil pan. That is a whole lot of work to fix. The breather box should be sitting flush with the block before you start the two bolts. Here is what the bottom side looks like when you pull it off. That o-ring is in there, but I did not see it at first!


To clean the intake manifold that connects to the flame trap, get a piece of wire or straighten out a small paper clip and clean out the vacuum orifice on that the small hose on the flame trap goes to. You need a vacuum in that line so when the throttle body plate is closed you have a vacuum on the block still via that little hose. I went so far as to put on the safety glasses and spray it out with throttle body cleaner. With the engine running you should be able to feel a suction on your fingertip.

Check the fitting on the top of the breather box where the flame trap plugs in, I had a Scamtech one that turned to soft mush after it was installed and let the flame trap pop off. Result was oil getting all over the place and a rough idle. Now have the IPD relocation kit installed so no longer an issue. You can see it sticking up in the picture.

Replace the dipstick o-ring, the oil cap seal, and any vacuum lines that are cracked or split, I ended up replacing all the vacuum lines on my 86. If you have a vacuum leak that can affect both idle and the engine block pressure. You need a good seal on the places air can get in the block and good tight vacuum on the air intake side to get a good negative pressure in the block.

Check the cam seal on the top back side of the engine. That can pop loose from excess pressure when it does oil will leak down the backside of the engine and make it look like your rear main is badly leaking (I have that merit badge from my pre-BB days). You can reach around the back side of the engine near the valve cover and feel it. I have added the bracket that prevents the cam from popping loose.

You can see the before picture where the my first effort at replacing the valve cover gasket went badly. A new cork gasket, some red gasket RTV, and using the BB suggestions fixed that one.

Good Luck and may the leak not be with you!

Paul

Here is the only pict I could find of before you can see where the valve cover was leaking.


This is from two weeks ago.