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05-08-2011, 03:45 PM | #21 |
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Re: Opinion on PCV valve for flathead?
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.
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05-08-2011, 10:05 PM | #22 |
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Re: Opinion on PCV valve for flathead?
How are you going to filter the incoming air?
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05-09-2011, 12:20 AM | #23 | |
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Re: Opinion on PCV valve for flathead?
Quote:
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. Last edited by 296 V8; 05-09-2011 at 09:24 PM. |
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05-09-2011, 07:45 AM | #24 | |
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Re: Opinion on PCV valve for flathead?
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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. |
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05-09-2011, 07:55 AM | #25 | |
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Re: Opinion on PCV valve for flathead?
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05-09-2011, 08:16 AM | #26 |
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Re: Opinion on PCV valve for flathead?
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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. Last edited by 36tbird; 05-09-2011 at 08:23 AM. |
05-09-2011, 08:31 AM | #27 | |
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Re: Opinion on PCV valve for flathead?
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05-09-2011, 11:06 AM | #28 |
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Re: Opinion on PCV valve for flathead?
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.
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05-09-2011, 11:13 AM | #29 |
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Re: Opinion on PCV valve for flathead?
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. |
05-09-2011, 11:41 AM | #30 | |
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Re: Opinion on PCV valve for flathead?
Quote:
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05-09-2011, 11:51 AM | #31 | |
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Re: Opinion on PCV valve for flathead?
Quote:
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. |
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05-09-2011, 12:07 PM | #32 |
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Re: Opinion on PCV valve for flathead?
This should clear up some pcv questions. Note there are two systems to choose from.
R |
05-09-2011, 12:19 PM | #33 |
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Re: Opinion on PCV valve for flathead?
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 Last edited by Jack E/NJ; 05-09-2011 at 01:18 PM. Reason: typos |
05-09-2011, 01:46 PM | #34 | |
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Re: Opinion on PCV valve for flathead?
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05-09-2011, 03:45 PM | #35 |
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Re: Opinion on PCV valve for flathead?
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.
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05-11-2011, 07:53 AM | #36 |
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Re: Opinion on PCV valve for flathead?
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.
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05-11-2011, 08:09 AM | #37 |
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Re: Opinion on PCV valve for flathead?
Butch, have you been running that set up very long?
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05-11-2011, 09:58 AM | #38 |
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Re: Opinion on PCV valve for flathead?
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05-11-2011, 10:30 AM | #39 |
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Re: Opinion on PCV valve for flathead?
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. Last edited by Jack E/NJ; 05-11-2011 at 03:44 PM. Reason: tp |
05-11-2011, 08:53 PM | #40 |
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Re: Opinion on PCV valve for flathead?
I think its a good idea.
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