There is not anywhere near enough vacuum in the air filter base to operate a PCV valve.It must be tapped into direct engine vacuum.It may work partially at higher engine RPM but at idle there is no vacuum to close the valve.If you have no place to hook the hose into like a carb spacer you could drill and tap for a hose nipple in the intake manifold in the centre area below the carb. The type of cap below can be used to create a true closed system.Run a fresh air feed hose from the base of the air flilter.The 64 truck valve is threaded and screws into the intake manifold.

  

Mike,

I used this (see photo) speedway motor breather cap with pcv and a draft tube on my 309ci Y.  Seems to be working fine.  I use it in the valley cover oil fill tube and run hose to carb spacer.

   

1956 F100 Big Window 309ci Y-block,  1956 F100 small window 272ci Y-block

Greg.  Mountains of North Eastern CA

If you are using a PCV system you need to take the draft tube off and plug the opening with a cup type plug.Having the draft tube AND PCV defeats the purpose of the closed engine crankcase ventilation system.Fresh air is supposed to be drawn in from the oil filler cap.If you leave the draft tube on fresh UNFILTERED  air is drawn IN from that source instead of the cap so you dont really get a fully ventilated engine.

  

Aside from all that dirty/unfiltered air contaminating the oil, when the system goes positive-pressure at high RPMs, the crankcase opening will likely pump out more oil, as the agitated lube (compared to the valley/valvecover space) is probably creating a heavy mist? Also, what might be the deleterious effects (if any) of the extra volume (vacuum driven) of cold fresh air injected into the lower crankcase?

6 VOLTS/POS. GRD. NW INDIANA

Ok,

Please help me understand.  If I block off the draft tube and run a pcv from back of valley cover and have a standard oil filler cap then wouldn't I just be pulling fresh "unfiltered" air through the cap and under valley pan into pcv and not venting the crankcase at all? 

I have a "filter" in the draft tube that is equivelant to the wire mesh common in the oil filler caps.  I also have vents in the valve covers.  It seems to me it would be better to pull the fresh air through the crankcase and valve covers and out the oil filler tube into the engine.  Seems like this would provide better "crankcase ventilation" to me.  What I'm not getting?  Thanks for the help. 

Mike I don't mean to hijack your thread.

   

1956 F100 Big Window 309ci Y-block,  1956 F100 small window 272ci Y-block

Greg.  Mountains of North Eastern CA

Greg, it isnt a hi jack, but even if it is so what.  I have done a few myself .

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

The cap itself is filtered with mesh which filters the incoming air.  The later model PCV systems went the extra step and ran a hose from the cap to the air cleaner to insure pure filtered air but tends to be overkill for a simple PCV valve retrofit.  The intent of bring fresh air in from the opposite side of the engine from where the PCV valve is located is to set up an air flow that will pick up moisture and other contaminants from the valley area of the engine.  Having the fresh air inlet and the PCV valve close together minimizes the amount of contaminants that can be pulled from the engine.  I believe that answers what you are asking?

Lorena, Texas (South of Waco)

Thanks Ted,

So what your saying is the way I have my engine set up is OK and would actually provide better evacuation of crank case "contaminants"?

   

1956 F100 Big Window 309ci Y-block,  1956 F100 small window 272ci Y-block

Greg.  Mountains of North Eastern CA

Do you park your truck in the garage?Do you notice the smell of oil and fumes when you open the door after its been kept closed overnite?When you close off the draft tube it seals the block and you wont get that smell anymore.One more reason to use a PCV system.

  

You make a valid point regarding vacuum signal.  What I was thinking of is a PCV with a very light spring (or maybe even simply an open line with a wire mesh filter) such that all but idle velocity would help vacate the "gases" in the valley and recirculate them in the combustion cycle.

This shouldnt create a "vacuum leak" senario as might a light spring PCV plumbed directly to the carb circuit or intake manifold. There should still be negative flow throught the oil filler cap, there should be less fumes into the air/garage, and with a PCV or mesh filter inline, it should minimize the heavy partical contaminants being re-introduced to the venturis.

Am I really way off track in my thinking?

Cheers... Brian

Cylinder Index = 84

Current Experiment = `57 Tbird, Grand Rapids, Michigan