PCV value hookup


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By rponfick - 3 Years Ago
I have researched the numerous postings on pcv valve systems, and have been amazed at the creativity of the individuals on the Forum.  My question relates to the choice of vacuum sources to attach to the valve.  The most popular source seems to be the plate that fits under the carb. with an attached vacuum connection (CASCO product).     
The '57 Tbird I recently acquired has the vacuum hose connected to the fitting at the back of the intake manifold where other vacuum sources are connected (power brake, vacuum advance, fuel pump).  A previous post indicated that the rear manifold was not a good place to use because it would cause the rear cylinders to run lean.  Is that really a concern, as the other vacuum sources are already attached there.  Does the pcv draw more air than the other components, and possibly cause a lean setting on some cylinders? 
Thanks, Ralph     
By DryLakesRacer - 3 Years Ago
I don’t believe a dual plane manifold which a stock Ford manifold is would know the difference as air from the carb air horn and the PVC valve would mix. Since the vacuum for the distributor and the power assist brakes are dead headed also they may not care either. 

However I have never seen a modern carb PCV valve and hose piggybacked on the same port of the carb with anything else and most are on the front. Most power brakes are on the back.  I’ve never had good luck using intake vacuum on a distributor. Every engine I’ve had runs and idles better on venturi vacuum. Your experiences may differ. 

I would like to add I believe modern carb and aftermarket have a hose fitting for the PVC system that is on the front 2 barrels of 4 barrel carbs where they spend 99% running paired to both sides of a dual plane intake. It is my thought the blow-by vapors are shared by all cylinders equally by mixing with the vaporized gasoline immediately thru openings in the base for it. It may have not been that way in the past with the exception of a 2 barrel which had its fitting on the rear with its PCV valve mounted on the carb base and not a rocker cover. 

 Today’s tuned port style has the PCV valve in the rocker cover and a hose right behind the throttle body which allows oil coating of the intake over time. “Catch Cans” can help in letting less oil vapor into the intakes and Ford Performance has engineered them for the 5.0 Coyote.
I do not know of mounted on a Ford Y-Block engine but I have sure thought about it. 
By charliemccraney - 3 Years Ago
A pcv valve is basically a controlled vacuum leak.  It is a source of intake air and fumes from the crankcase and will alter the mixture of the cylinders it is nearest.  Most other vacuum devices, like advance mechanisms, brake boosters, etc do not draw air or other gases through and therefore will not affect the mixture when in good working order.
By rponfick - 3 Years Ago
To further clarify my pcv hookup, see photo below. 
http://forums.y-blocksforever.com/uploads/images/2040b239-ef06-45f1-9789-43a.jpeg
hooked up to rear manifold port is power Brake line and pcv hose.  Small orange hose is vacuum to distributor. Car seems to run well on manifold vacuum.  Vacuum hose from fuel pump is not hooked up to anything.  This is an unusual hookup, but that is how it came to me.  
Carb is stock 1273, which has no vacuum ports for pcv, or other hookups. 
I plan to check rear cylinder spark plugs for lean running. 
Any more comments. 
Thanks, Ralph