Runaway!

[air-cooled or diesel]

checking the main and vac connections is fairly simple; a compression test is more difficult. both. the vac if theres any leak @brake booster, or the line; this too can happen, and lead to a runaway situation; takes a few minutes to check vac connections, brake booster connection, and possibly brake booster, as the leak will pressurize crankcase and can blow oil out of vent.

[RabbitJockey]

u might be able to solve the issue more venting and a cam splash guard.

[burn_your_money]

...check vac pump and connections, a leak here can push oil into the intake as well,,

As if the vac doesn't vent into the crankcase already?

The vac system is suppose to be closed, which means the vac pump isn't actually pumping air into the crankcase, except to make up for when vacuum is used.

Try pulling your main vacuum hose and reving the engine up. Your disptick will probably push out of its tube.

[Smoker]

u might be able to solve the issue more venting and a cam splash guard.

The more I think about the splash guard, the more it makes sense. I mean there's no filter or anything on the vent outlet, and the cam is slinging oil everywhere... how is it NOT going to end up in the intake?

[Smoker]

...check vac pump and connections, a leak here can push oil into the intake as well,,

As if the vac doesn't vent into the crankcase already?

The vac system is suppose to be closed, which means the vac pump isn't actually pumping air into the crankcase, except to make up for when vacuum is used.

Try pulling your main vacuum hose and reving the engine up. Your disptick will probably push out of its tube.

You mean pull the main line off the vac pump? If it pushes the dipstick out, what does that tell me? For some reason, the logic of this aspect of an engine has always escaped me.

[air-cooled or diesel]

The vac system is suppose to be closed, which means the vac pump isn't actually pumping air into the crankcase, except to make up for when vacuum is used.

if @brake booster or hard line, if theres enough of a leak it will pressurize the crankcase; separate of motor mind you, it ll suck air in and send it to the cc, usually it will push oil out of dipstick, and perhaps more. its not hard to check and if its not the problem, you checked, should take a few minutes, a light a mirror and a pair of eyes. if it does happen to be the problem, it could be, if not its going to be a question of the rings, compression test.
a splash guard over cam helps with oil coming up out of vent, but if its enough to run the engine on its own, i doubt this is the only problem.