PCV systems correctly done are always sucking their air from filtered side of the air cleaner from the factory. Many of the ones retrofitted to earlier engines just use a rocker cover breather. One way to check your system is to remove your “breather” at idle and put a piece of paper over the hole. The suction thru the system should hold the paper. In 1963-4 when I installed many aftermarket systems on earlier vehicles we had a plastic device with a ball that moved to prove the system worked before it left our shop. A requirement from the State of California.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

yes, as you notice, that cap is not vented so if you run the tube to the "clean" side of the air filter you will suck clean air into the motor and out through a PCV system. I saw this set up on a truck motor.

If you’ll vent that oil fill tube nipple to the air cleaner, that will do the job for that.  Adding a PCV valve elsewhere on the engine will complete the system.

Lorena, Texas (South of Waco)

Thanks for all of your replies! No, the provision for the road draft tube is not bored, but I do have a vent tube in the rear of the valley pan that had a breather on it. I'm thinking in line PCV on the filler with the breather on the back.

I like to see some air move through the engine to scavenge water vapor from the blow by before it condenses inside the engine

It may not have  been that important on a generator engine that comes up to rated speed as soon as it's started and warms up fast but in a classic car that does not do long trips the oil will become contaminated real fast without proper crankcase ventilation.

When PCV systems first appeared they were thought of as emission systems and rapidly  removed by owners, truth is they did provide a scavenging effect that was good for the life of the engine by keeping moisture sludge out of the oil.

I use a breather cap with a hose fitting, attached a 90 degree 1/2 hose fitting under my air cleaner, and connected the 2 with a hose. I do not have a PCV system and it keeps the vapors from under the hood and the smell away. I’m sure that’s what it was on the industrial engine.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

If you use that port on the oil fill tube you must provide some way to admit fresh air into the engine, A vented valve cover or 2 would work.

In a car PCV application the PVC valve would be in the back of the valley cover and the fresh air would come from a vented oil fill cap

I assume that there is no opening on the engine at the front left corner where a road draft tube would have been located, industrial engines either do not have that hole bored or have a blank off plate

I have also seen that port run to the air cleaner (before filter). It's another way to scavenge crankcase fumes of course.

Daniel Jessup

Lancaster, California

aka "The Hot Rod Reverend"
check out the 1955 Ford Fairlane build at www.hotrodreverend.com

Yes, that is correct. Put on a PVC and hook it to the vacuum port on thr bottom of the carb.
Tim
Hot 'n Humid 
Florida 33706 

Ok, stupid question of the day....Where does this vent tube connect to? This was an industrial engine that was originally in a generator and somewhere along the line, found it's way into a 1954 Crestline. It was not connected to anything when I got the car. I'm thinking that's a bad thing, so here I am. I was thinking maybe running it to the throttle body with an inline PCV valve.