Packard Forum Index » Modification Discussion

Turbopackman wrote:
I used a rubber grommet from a 1965-66 Buick 401 0r 425 valve cover, the one on the front left valve cover.

I really think the little breather inside the air cleaner worked not only to allow filtered air into the crankcase, but also to move gases back into the carb at road speeds, when there is a vacuum produced inside the air cleaner and the crankcase pressure goes up. Anyone who has had this old setup has seen that a little bit of oil often pools in the bottom of the air cleaner housing, and also a black spot forms on the air filter itself, opposite the hole. I think what this hole really does is allow the pressure in the crankcase to self-balance for different engine RPMs and manifold pressures. No timing changes required! No vacuum leaks!

BH wrote:
55PackardGuy wrote:

Quote:

I really think the little breather inside the air cleaner worked not only to allow filtered air into the crankcase, but also to move gases back into the carb at road speeds, when there is a vacuum produced inside the air cleaner and the crankcase pressure goes up. Anyone who has had this old setup has seen that a little bit of oil often pools in the bottom of the air cleaner housing, and also a black spot forms on the air filter itself, opposite the hole. I think what this hole really does is allow the pressure in the crankcase to self-balance for different engine RPMs and manifold pressures. No timing changes required! No vacuum leaks!

I'm no engineer, but not sure that this is entirely correct.

What you're describing, in this case, is a closed PCV system, and I'll agree that, when the PCV valve is closed, a closed sytem is designed to accept excess crankcase vapors, through the air cleaner, that would have otherwise been expelled into the atmosphere with the earlier, open systems.

However, the presence of liquid oil in the air cleaner, coming from the breather, could be a sign of trouble.

A clogged PCV valve or collapsed PCV hose would cause too much crankcase vapor to go the wrong way through the breather. Excessive blow-by in the engine, for any variety of other reasons, would also cause this.