PCV on 8BA
- Thread starter Robert Legner
- Start date
Robert Legner
Member
V8 Bob, I think what Jack E/NJ is trying to do is take care of fumes that drift out of the filler tube when the car is at idle. At idle the draft tube is not in use because the car is not in motion, so if the filler tube is connected to the air cleaner that would to some great degree burn those fumes. When the car is in motion then the filler tube would indeed allow air to move down through the engine ventilating the crankcase. In that case the air would move from the air cleaner into the engine and out the draft tube. I agree connecting the filler tube to the air cleaner is not a PCV system.
51 MERC-CT
Well-known member
My PCV system does indeed use a Chrysler filler cap on the filler tube connected to the outer plenum of my air cleaner.
This is the same PCV system that Chrysler used and Ford used the same PCV system with the hose from the air cleaner to the oil filler cap on the overhead valve cover.
JSeery
Member Emeritus
A PCV by definition is a closed system that uses engine vacuum to pull air out of the crankcase. Believe what you are referring uses the air cleaner intake source for a PCV that draws the air from a fitting on the air cleaner via a oil filler cap on the valve cover. The suggested approach posted here is the reverse of that setup, it is using the slight vacuum within the air cleaner to draw air out of the crankcase without the use of a PCV valve.
An issue with this approach, to me, is you are pulling unfiltered air into the crankcase!
Back to the original post, are you sure you are using a correct PCV valve, one that is compatible with a flathead? Are you sure it is working correctly? The low vacuum you are seeing at idle would indicate it is not working properly. The valve should block the vacuum source at idle.
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V8 Bob
Well-known member
The early '60s pcvs were open, with the air intake "open" to the engine compartment. The later closed systems did run filtered intake air from the air cleaner by using a modified fill cap on a valve cover, like the Chrysler style some on this thread are using. But the ventilation used engine vacuum acting on a pcv, not road draft.
The flathead pictured is modified '35-'48, different from an 8BA, and not a good way to plumb a pcv on the early V8s. However, creating any vacuum on a stock 8BA fill cap could result in pulling unfiltered dirty air up the road draft and into the engine-not good
JSeery
Member Emeritus
Maybe I am just being picky, but the 35-48 diagram posted is not a PCV setup in any way, shape or form. It is a modification to the road draft system, nothing Positive about it. Total agreement on it not being a good setup because of the infiltration of unfiltered air!
Jack E/NJ
Well-known member
A pan vent filter is in fact on the diagram posted earlier. Same mesh-type as used in vented oil filler caps only stainless steel. So it's no better no worse at filtering fresh air into the crankcase than the original setup
As Robert suggested earlier, it simply entrains fumes into the intake draft when road draft is weak. It's not high manifold vacuum. So pressure differential is nil and works the other way when road draft is strong.
It's only purpose is to keep crankcase stink out of the engine compartment & cabin with minimal alteration of original venting setup.
Jack E/NJ
As Robert suggested earlier, it simply entrains fumes into the intake draft when road draft is weak. It's not high manifold vacuum. So pressure differential is nil and works the other way when road draft is strong.
It's only purpose is to keep crankcase stink out of the engine compartment & cabin with minimal alteration of original venting setup.
Jack E/NJ
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51 MERC-CT
Well-known member
This is an operational PCV system on an 8BA type engine like the OP engine. Not a 59AB type.
Robert Legner
Member
Jack E/NJ, does the chrysler chrome cap have wire mesh inside? If it does it would certainly filter out dust if the mesh is oiled. Air moving toward the engine air filter would be filtered the same as the original set up when the road draft draw is strong pulling air in through the oil filler cap when the car is in motion.
Jack E/NJ
Well-known member
>>>does the chrysler chrome cap have wire mesh inside?>>>
All the hose-barbed caps have mesh for air filtration & crankcase backfire prevention. Some have metal, some fiberglass. Mine has a Scotchbrite stainless steel scrubbing pad from the super market both inside the filler cap and stuffed around the pan vent. GB tried it out on one of his trucks with a bit too much stinky blowby entering the cab. https://www.fordbarn.com/forum/showpost.php?p=1675116&postcount=5
Jack E/NJ
All the hose-barbed caps have mesh for air filtration & crankcase backfire prevention. Some have metal, some fiberglass. Mine has a Scotchbrite stainless steel scrubbing pad from the super market both inside the filler cap and stuffed around the pan vent. GB tried it out on one of his trucks with a bit too much stinky blowby entering the cab. https://www.fordbarn.com/forum/showpost.php?p=1675116&postcount=5
Jack E/NJ
Robert Legner
Member
Thank you Jack E/NJ
V8 Bob
Well-known member
The best thing to do is get the pc valve working like it should. Creating plumbing that simply removes "stink" and vapors from the engine compartment is a waste of time, imo. Eliminating the road draft will accomplish that and much more. The engine, oil and environment will all benefit. 
I've done a couple 8BA's with a pcv. I had the intake set up by Baxter Ford Parts and on both he put a freeze plug drilled for a pcv grommet in the road draft hole and ran a hard line around to the right side of the manifold and tapped into the manifold under the center carb. I then used a vented cap on the top of the fuelpump riser for air and filling with oil. On these engines I used the Bubba converted Chevy distributor with mechanical advance. Both engines seemed to run and perform fine?
Robert Legner
Member
V8 Bob, I bought the PCV system from the link on Ford Barn, so I figured it would be correct.....JSeery questions if I have the correct PCV valve. The one I have draws vacuum even at idle. So what is the correct valve. If the valve does not draw some vacuum at idle then where does that blowby go. It seems there should be some vacuum at idle to take the fumes away. Someone tell me what valve to buy. Thank you all for your input, it is invaluable. I am trying to solve this.
34PKUP
Well-known member
The valve you bought is correct for your application.
It will and should pull the most vacuum at IDLE and the least while pulling power.
51 MERC-CT
Well-known member
Totally agree.
This is a test that was done to confirm the presence or crankcase vacuum.
Flathead Fever
Well-known member
The PCV valve is extremely important for preventing your oil from turning into sludge. I'm not a big fan of how they look on a vintage flathead but they will absolutely increase the lifespan of the engine.
The air fuel ratio will change some with the installation of a PCV valve. Its going to lean it out a little. You will need to adjust your idle A/F mixture screws and your idle speed screw to compensate for the controlled vacuum leak you just installed. At idle the PCV valve is almost closed, this is when Intake manifold vacuum is high. The vacuum closes the valve to its smallest opening so it does not lean out the mixture that much at idle.
As the speed increases the vacuum drops off allowing a spring to open the valve further, when the blow-by is at its greatest and the engine can handle burning the excessive blow-by.
The only thing that goes wrong with a PCV valve is it can get stuck in the wide open position which will allow too much air to flow at idle. The engine will die or run extremely rough at idle. If you pinch off the hose to the PCV valve or stick your finger over the end of the valve and the idle straightens right out you have a bad PCV valve. It should rattle when you shake it. Also over time the spring weakens and the valve looses its calibration allowing too much air flow at lower operating speeds. They are a maintenance item that need to be replaced probably every 50K miles on a daily driver.
Choose a valve from an engine that is close to the same cubic inch as your flathead. It will be designed to flow the correct amount of air for that cubic inch s without leaning out the engine too much
On an overhead V8 like a 302 Ford the PCV valve plugs into a rubber grommet in the valve cover. The valve is connected by a hose that is compatible with fuel and oil, Heater hose will swell up and turn soft. The vacuum will then be able to collapse the hose. Use fuel or emission hose only. The vacuum source hose is plumbed directly beneath the carburetor so it feeds all the cylinders evenly and does not lean out any one cylinder.
Look at the illustration on post #24, See how its designed to pull air from one side of the engine to the other the other-side to purge the crankcase. You want to try and create a flow like this inside your flathead. You do not want to mount the fresh air inlet too close to the PCV valve otherwise the PCV valve will just be sucking in the incoming air and not the crankcase fumes.
There are open PCV systems and closed PCV systems. The difference being if the oil breather has a hose connected to the air filter. The early open systems allowed excess blow-by to go out the breather cap and into the atmosphere. That was creating smog so they closed the system. The closed system routed any excessive blow-by that the PCV valve could not handle out the oil breather cap, through a hose and into the air cleaner where it gets sucked into the engine and burned. One of the most common failed items on a smog test is somebody replacing the closed type oil breather cap with a chromed open style one that allows blow-by to escape to the atmosphere. You need to make sure you install a closed style breather cap.
In order for the PCV valve to suck air out of the crankcase there needs to be fresh air allowed to flow into crankcase. This filtered air flows from the air filter on the opposite side of the engine, through the breather cap and into the crankcase. Like I said before, its important that the fresh air going into the crankcase is at one end or one side of the engine and the PCV valve is on the opposite side so there is a nice continuous flow going through the crankcase. If its working good you can pull the breather and lay a sheet of paper over the tube and it will suck the paper down.
They make a couple of difference hose connections to convert your air cleaner into a PCV system. Mr Gasket makes one that you drill a hole in the air cleaner base and bolt on the hose connection. You need a good sized air cleaner so the drilled hole will be after the air has gone through the filter. If you have small hot rod air cleaners K&N makes PCV breathers you could adapt to the push on oil cap. This way you could eliminate that filtered air hose from the air cleaner.
The air fuel ratio will change some with the installation of a PCV valve. Its going to lean it out a little. You will need to adjust your idle A/F mixture screws and your idle speed screw to compensate for the controlled vacuum leak you just installed. At idle the PCV valve is almost closed, this is when Intake manifold vacuum is high. The vacuum closes the valve to its smallest opening so it does not lean out the mixture that much at idle.
As the speed increases the vacuum drops off allowing a spring to open the valve further, when the blow-by is at its greatest and the engine can handle burning the excessive blow-by.
The only thing that goes wrong with a PCV valve is it can get stuck in the wide open position which will allow too much air to flow at idle. The engine will die or run extremely rough at idle. If you pinch off the hose to the PCV valve or stick your finger over the end of the valve and the idle straightens right out you have a bad PCV valve. It should rattle when you shake it. Also over time the spring weakens and the valve looses its calibration allowing too much air flow at lower operating speeds. They are a maintenance item that need to be replaced probably every 50K miles on a daily driver.
Choose a valve from an engine that is close to the same cubic inch as your flathead. It will be designed to flow the correct amount of air for that cubic inch s without leaning out the engine too much
On an overhead V8 like a 302 Ford the PCV valve plugs into a rubber grommet in the valve cover. The valve is connected by a hose that is compatible with fuel and oil, Heater hose will swell up and turn soft. The vacuum will then be able to collapse the hose. Use fuel or emission hose only. The vacuum source hose is plumbed directly beneath the carburetor so it feeds all the cylinders evenly and does not lean out any one cylinder.
Look at the illustration on post #24, See how its designed to pull air from one side of the engine to the other the other-side to purge the crankcase. You want to try and create a flow like this inside your flathead. You do not want to mount the fresh air inlet too close to the PCV valve otherwise the PCV valve will just be sucking in the incoming air and not the crankcase fumes.
There are open PCV systems and closed PCV systems. The difference being if the oil breather has a hose connected to the air filter. The early open systems allowed excess blow-by to go out the breather cap and into the atmosphere. That was creating smog so they closed the system. The closed system routed any excessive blow-by that the PCV valve could not handle out the oil breather cap, through a hose and into the air cleaner where it gets sucked into the engine and burned. One of the most common failed items on a smog test is somebody replacing the closed type oil breather cap with a chromed open style one that allows blow-by to escape to the atmosphere. You need to make sure you install a closed style breather cap.
In order for the PCV valve to suck air out of the crankcase there needs to be fresh air allowed to flow into crankcase. This filtered air flows from the air filter on the opposite side of the engine, through the breather cap and into the crankcase. Like I said before, its important that the fresh air going into the crankcase is at one end or one side of the engine and the PCV valve is on the opposite side so there is a nice continuous flow going through the crankcase. If its working good you can pull the breather and lay a sheet of paper over the tube and it will suck the paper down.
They make a couple of difference hose connections to convert your air cleaner into a PCV system. Mr Gasket makes one that you drill a hole in the air cleaner base and bolt on the hose connection. You need a good sized air cleaner so the drilled hole will be after the air has gone through the filter. If you have small hot rod air cleaners K&N makes PCV breathers you could adapt to the push on oil cap. This way you could eliminate that filtered air hose from the air cleaner.
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51 MERC-CT
Well-known member
Don't think it's "extremely" important for preventing oil from turning into sludge.
It would do that even if left wide open.
It is extremely important to prevent any backfire from blowing your engine apart while igniting crankcase gasses.