I have what I thought to be a head gasket leak. I Havnt taken it off and properly resealed head gasket but I did retorque and change rocker gaskets and pushrod seals. I lost a rocker cap riding hard and the oil leak stopped cold. Is this a pressure isssue causing it to push oil out somwhere bacause of pressure buildup. 71 t120 ,morgo 75o top , high comp pistons, Stock cams, stock valves . I never checked the head for warpage because it had been recut and has new valves. Only venting I know of is primary and the shared oil thru the crankcase to primary. I.am still gonna pull the head again but I'm wondering if I can vent a rocker cap. The leak is minor , comp . Is great and it runs like a raped ape...Ken. with rocker cap off ran like a beast.
Ps, I have retorque thru heat cycles and used more torque up to 38lbs or so and did it from the get go. About 250 miles on the breakin and I think rings are good.
I vented a cap and took if for a spin it worked great. No.more leaks the rocker is getting oiled so it must be returning. Ran better than ever. Just vented one cap on the exhaust side. Pipes are dry inside for the first time..
You might find that someone has fitted an oil seal between the crankcase and primary case.The drive-side crankcase was still bored with the seal diameter,even though the seal was left out from 1970 to allow breathing through the primary.
If someone mistakenly fitted a seal behind the crank sprocket,you have no breather.
worn or improperly reamed valve guides can cause excessive pressure and oil leaks on the exhaust side, and oil consumption and smoking on the intake side.
I have heard that the proper exhaust rocker box pressure is used to push the oil back down the pushrod tubes.
I have had this engine rebuilt and the it shares oil in the primary still Mr. Pete. I'm gonna looks at the valve guides too when I take the head off again. I just added an open hole so if it fills and doesn't return its gonna come out the cap I would imagine. ill just keep an eye out. Thanks for the input .. i have heard good things about using 50 wieght oil and champion plugs for hot weather. I am going to try a cooler plug to see what happens.