Nope, the back scoop will be blocked off. Just on there for looks. Sorry, I should have pointed that out. Outside air will be coming in from oil pan vent. Also, I am running a tube down inside the filler hole so that I will give priority to crankcase not lifter valley but that probably doesn't matter given the holes in the lifter valley that go to the crankcase.
Opinion on PCV valve for flathead?
- Thread starter BobM
- Start date
296 V8
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I am running an 8BA w/ an early Eddie Meyer intake. I capped off the road draft tube w/ an elbow fitting and then drilled a hole into the center runners of the intake and installed a threaded PCV valve. It really cut down on the blow by, and it is hidden.
I did one exactly like this and it sucked up oil and smoked real bad
I removed the hose and built a baffle (attached to the gasket) over the valve and just pulled the blow by from the valley.
A big part of a PCV valves job is to save the engine from exploding if it backfires…..it is a check valve.
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V8 Bob
Well-known member
You never want to pull air into the engine through the road draft on any engine. Why would you?
On 8BA's, the pcv replaces the road draft tube at the intake. On the '35-'48s, closing up the pan vent and adding the pcv there, as Newc did, is probably the best on these engines. The engines will now vent as designed, even though the air flow inside differs.Air can be drawn in through the stock oil fill cap, or from the air cleaner, as late 60's cars began to do. (this is known as a "closed" pcv system).
No late model car uses two pcvs that I have ever seen. What may look like a pcv is simply a fitting off the sealed valve cover cap or grommet that goes to the air cleaner. The actual pcv always is plumbed to manifold vacuum. There would be no air flow running two pcvs.
V8 Bob
Well-known member
Not sure what you're logic is on trying to pull air into the 59 pan vent, but you do know that the early pan vents ('35-'48) go directly to the valve chest, not the crankcase, like the later 8BAs? What you describe above will give priority to the valve chest.
Here's my thinking. Air coming in from the oil pan vent with a foam filter around it. That air goes up into the lifter valley. There are holes in the lifter valley that go down to the crank case, right? Now, with the stock type tube that goes down from the fuel pump tower mount into the block at the rear of the lifter valley and my oil filler cap unvented, the air cleaner tube with the PCV will be sucking on the crank case air. This is the same venting system route as stock, except in reverse.
Jack E/NJ has been running with this sort of set up except that he is not using a PCV. Hopefully the PCV I chose will work OK and I think by having it mounted horizontally the little check ball in there is more sensitive to the lower vacuum I am using from the air filter. That is, if it were mounted vertically, it would have gravity to overcome to move the marble. We'll see.
Jack E/NJ has been running with this sort of set up except that he is not using a PCV. Hopefully the PCV I chose will work OK and I think by having it mounted horizontally the little check ball in there is more sensitive to the lower vacuum I am using from the air filter. That is, if it were mounted vertically, it would have gravity to overcome to move the marble. We'll see.
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V8 Bob
Well-known member
My main question is what possible advantage is there reversing the vent system air flow, and taking in air near the road through the early pan vent or 8BA draft tube?
Roger/Sacramento
Senior Member
The purpose of this discussion is to remove blowby from the valley/crankcase. I don't like the idea of running the dirty air into the intake manifold. You also must consider the size of and maintenance of a PCV valve. I have an idea of running a tube from the draft tube location to a fitting on the exhaust pipe extension (past the exhaust manifold). The idea of lubricating the top cylinders is better done with Marvel Mystery Oil in the gas tank. My idea eliminates the possibility of wrong engineering.
The advantage is not drawing manifold vacuum off for a PCV. Also, I am not running a long tube from the air cleaner to the oil pan vent. I want to preserve my manifold vacuum for the Chevy distributor that I will be running. My feeble brain tells me that keeping your manifold vacuum as high as possible will add to the efficiency of your engine. Some people hang out at pool halls, I'll be hanging out trying to tune my flathead for the best efficiency using the old Strombergs.
You imply that "taking in air near the road" is a problem. I'm not lowering the front of this project that much where I think there would be some issues. Also, I think that there is enough air turbulence around front sheet metal, frame crossmembers, radiator, etc and our ground speed is not so high that a low pressure area around the pan vent would cause ambient air to not be available.
You imply that "taking in air near the road" is a problem. I'm not lowering the front of this project that much where I think there would be some issues. Also, I think that there is enough air turbulence around front sheet metal, frame crossmembers, radiator, etc and our ground speed is not so high that a low pressure area around the pan vent would cause ambient air to not be available.
Would braking and acceleration effect the check valve if mounted horizontally?
V8 Bob
Well-known member
If you ever connected a vacuum gauge to the manifold, and measured the level before and after connecting a properly sized pcv, you would realize there is NO loss of measurable vacuum. You're concerned about something that doesn’t exist.
Along with the worst area to pull air into the engine, the 8BA draft tube and earlier pan vent act like pitot tubes, because of the partial vacuum developed by air flow when vehicle speeds reach about 30 mph and higher. You're not going to get near the needed amount of air into the engine by this "reverse engineering", if any at all, during high speeds.
With no disrespect intended, some things are not a good idea, and this is definitely one of them. Adding a pcv in place of the draft tube or pan vent is the best and simplest way to provide ample and beneficial ventilation in pre-pcv vehicles.
Jack E/NJ
Well-known member
V8 Bob>>>My main question is what possible advantage is there reversing the vent system air flow, and taking in air near the road through the early pan vent or 8BA draft tube?>>>
The advantage is positive as opposed to passive crankcase ventilation.
Roger/Sacramento>>>You also must consider the size of and maintenance of a PCV valve.>>>You also must consider the size of and maintenance of a PCV valve. I have an idea of running a tube from the draft tube location to a fitting on the exhaust pipe extension (past the exhaust manifold). The idea of lubricating the top cylinders is better done with Marvel Mystery Oil in the gas tank.>>>
As Ronnie suggests above, you may choose to use a valve like Lou did or NOT. I chose NOT to use a valve in the tube connecting the pump stand to the air-cleaner cannister. This tube is filled with stainless steel mesh to prevent backfire into the crankcase and retard oil mist into the air cleaner. This is in fact similar to the first low-vacuum positive ventilation systems in the late 50s before the elimination of the open-crankcase draft tube and before the introduction of the closed-crankcase high-vacuum PCV valve. This early positive ventilation system was still used in combination with the closed-crankcase PCV valve well into the 70s and 80s because it works when the PCV valve doesn't at near WOT when blowby is greatest.
Roger's idea of venting the crankcase with an exhaust venturi seems like a good one.
Jack E/NJ
The advantage is positive as opposed to passive crankcase ventilation.
Roger/Sacramento>>>You also must consider the size of and maintenance of a PCV valve.>>>You also must consider the size of and maintenance of a PCV valve. I have an idea of running a tube from the draft tube location to a fitting on the exhaust pipe extension (past the exhaust manifold). The idea of lubricating the top cylinders is better done with Marvel Mystery Oil in the gas tank.>>>
As Ronnie suggests above, you may choose to use a valve like Lou did or NOT. I chose NOT to use a valve in the tube connecting the pump stand to the air-cleaner cannister. This tube is filled with stainless steel mesh to prevent backfire into the crankcase and retard oil mist into the air cleaner. This is in fact similar to the first low-vacuum positive ventilation systems in the late 50s before the elimination of the open-crankcase draft tube and before the introduction of the closed-crankcase high-vacuum PCV valve. This early positive ventilation system was still used in combination with the closed-crankcase PCV valve well into the 70s and 80s because it works when the PCV valve doesn't at near WOT when blowby is greatest.
Roger's idea of venting the crankcase with an exhaust venturi seems like a good one.
Jack E/NJ
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flatjack9
Well-known member
Your problem is going to be that you will get no flow through that PCV valve because there is no vacuum to operate it. The PVC valve consists of a variable diameter pintle and a spring both of which are calibrated to the engine it is used on. It makes no difference if the valve is horizontal, vertical or upside down. The spring needs the vacuum working against it to open the valve. When the engine is off, the spring pushes the pintle shut and this is the position yours will be in. Install a vacuum gauge inside the air cleaner and you will see where your problem lies. Jack's system works because he doesn't have a valve to block any flow.
Have you ever sucked on a PCV? The one I got allows air through without any noticeable resistance. However, if you blow into it to simulate a backfire, it slams shut. That is it's real purpose to be able to slam shut. I feel that the intake vacuum in an air cleaner will be more than adequate to keep the PCV open. Jack's idea of reverse flow that I stole to make up my set up, subscribes to the KISS theory and does not need to be over thought.
Butch11443
Senior Member
I use a pvc on an 8BA type intake where the road draft tube is. I have a closed oil fill cap with the tube going to the bottom of the air filter. Simple and works excellent.
Butch
Butch
51 MERC-CT
Well-known member
Do you have a vacuum source going to the pcv valve? If so to where?
Jack E/NJ
Well-known member
Butch>>>I use a pvc on an 8BA type intake where the road draft tube is. I have a closed oil fill cap with the tube going to the bottom of the air filter. Simple and works excellent.>>>
IMO, Butch's setup is a proper way for achieving positive ventilation in a closed-crankcase using a PCV valve. To avoid altering the pan's draft vent to accomodate the valve, the valve might also be re-located at the end of the dipstick tube with a rubber grommet and the pan vent simply plugged. The valve would then be closer to manifold vacuum and easily removed for checking oil level.
Jack E
PS to Lou: If you want to try a closed-crankcase PCV, you could keep your setup as-is. Just add another valve on the dipstick tube to manifold vacuum, plug the pan vent, and either keep your present valve to the pumpstand or fill the tube with mesh to prevent backfire.
IMO, Butch's setup is a proper way for achieving positive ventilation in a closed-crankcase using a PCV valve. To avoid altering the pan's draft vent to accomodate the valve, the valve might also be re-located at the end of the dipstick tube with a rubber grommet and the pan vent simply plugged. The valve would then be closer to manifold vacuum and easily removed for checking oil level.
Jack E
PS to Lou: If you want to try a closed-crankcase PCV, you could keep your setup as-is. Just add another valve on the dipstick tube to manifold vacuum, plug the pan vent, and either keep your present valve to the pumpstand or fill the tube with mesh to prevent backfire.
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