Positive Crankcase Ventilation (PCV) valves

[Tony Wheeler]

I'm not familiar with PCV valve design, but I'm guessing it's a bypass passage designed to provide a degree of crankcase ventilation at high vacuum, ie. under light throttle. In other words, a transition passage between idle and load conditions, just like carbies have for fuel metering. Obviously it would act as an air bleed at idle, but presumably it's small enough to be compensated by readjustment of the idle speed and mixture screws. Anyway it's obviously designed that way so it would be worth trying before changing the plunger.

[Jacques Reed]

Not familiar with the Chev Blitz PCV valve setup but here are two types that I know of used on Ford sidevalve/flathead V8 engines.

One type has the PCV valve feeding directly into the manifold at the rear side of the carby and the other has a spectacle piece between the carby and manifold and the PCV valve is fed into the front side of this piece just below the carby.

This front feed is the same as shown in my Ford CMP parts and maintenance manuals.

Hope this is of some interest.

Cheers,

Jacques

[Jordan Baker]

Grant.

Just wondering if you had any luck with regards to these PCV valves? I’m missing one for my engine

[Lynn Eades]

Jordan, This might help? The Ford flathead ones rely on gravity (have no spring in them) so they have to be mounted vertically (and the right way up)

[Owen Evans]

Originally Posted by Jordan Baker

Grant.

Just wondering if you had any luck with regards to these PCV valves? I’m missing one for my engine

Jordan,

The attached shows the Chevrolet setup. This valve also has no spring inside it, but is helpfully marked with an arrow next to the word 'UP'. It is a sealed unit, but I believe there is a later type that screws together. I could find no part number on my valve, but it is marked with 'Donaldson Co. Inc., St Paul, USA', if that helps.

Check out sections K4 and K5 of the MB-C1 maintenance manual for some more info, including a schematic of the valve.

Owen.

[Brian Gough]

Jordan

I have one (and am also looking for a replacement) similar to what Owen posted the picture of.

Markings on it are:

near the "UP" - " DONALDSON CO INC ST PAUL U.S.A. "

near the bottom - " U S PAT. 2120050 CAN PAT 378550 "



Brian