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PCV


ralphnof49

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Seems like you would need to add a hole and hose connection in the carburetor spacer. Connect the hose to the suction side of a PCV valve. You could then use the pipe between the manifold and the oil bath air cleaner to hook up the crankcase end of a PCV valve.

The question I have, is with 12 tiny pistons, is there more or less vacuum than with 8 larger ones of an approximately 292 V-8? This would help with selection of the proper size PCV valve.

Sludge seems to be a problem with the V-12. I get a lot of blowby out the oil fill tube, smells bad too. A proper PCV valve should relieve these problems. One of the new replacement 4-barrel manifolds would make it easier, as you could find a stock late model spacer set up for a PCV connection.

Abe

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I'm using a PCV valve designed for a 292-302 cubic inch Ford and it works fine with little or no effect on the V12. I think the sizing of PCV valves are more a function of engine size rather than engine design. This set up seems to have completely eliminated any blow by on my old engine.

Here's a new set up I will be using in the future. The spacer plate is a water-heated Ford unit with a PCV port. I have moved the "vent" point to the front of the manifold to induce air flow thru the entire valve chamber rather than use the regular vent futher back. There is also a "dam" on the bottom side of the manifold forcing flow thru the valve chamber and up thru a hole in the front of the manifold gasket.

I think you can use the vent hole on the original intake manifold if the area forward between the gasket and the manifold is "clear" and there's air flow thru the valve chamber up thru the hole in the forward end of the gasket. The bottom of the original manifold fits against the gasket so there's not much, if any, flow by-passing the valve chamber.

post-31684-143138186403_thumb.jpg

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Thanks for the replies. I will try Jake Fleming.

Peecher, is the vent on the front of the manifold the plug on the driver's side at the side of the manifold? Could one run the intake into the plug on top of the manifold in front of the carburetor? That would be pretty simple, once the fittings are found.

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The "vent" on the stock manifold is the 1/2" hole on the right side near the front. The little "plugs" on the left side of the manifold are there because the factory drilled "equalizing" holes between the 2 intake runners on either end of the manifold and had to plug the "access" hole. As far as using the port on top of the manifold I too thought that would be the easiest but I believe the vacuum source should be as far "upstream" as possible so as to evenly distribute and mix the "fumes". All the modern set ups I've seen are done this way. The slight "leaning" effect would also be evenly distributed. A spacer plate with vacuum port(s) similar to that used for Columbia Axle control would work and I think these are available from after market sources. The forward port on the stock manifold is fairly close to the carburetor and it does access both left and right intake runners so it might work. I think I would drill down thru it and to open it up a bit though. A 1/4" pipe thread fitting could be used in that port with some sealer.

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My stock manifold does not have another potential vent opening on the right side near the front. I talked with Jake and he makes a kit that requires a new "vent" port to be drilled near the front of the manifold. One has to remove the manifold to drill the hole. The intake port can then be the existing cap on top of the manifold in front of the carburetor. Pre war and post war manifolds are different.

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You must have an early manifold on your '47? I have never seen a '42 to '48 4-bolt carb manifold that didn't have the vent? The '41 and older cars used the forward manifold vacuum port for the distributor vacuum brake so I don't know how suitable it would be to also use this for venting fumes? This port was plugged on '42 to '48 cars so it could be used.

The manifold on the left is an early ('38 ?) and does not have the vent.

post-31684-143138187238_thumb.jpg

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Thanks for pictures, I did not see the port you referred to before. The hole is open, not plugged with anything. The gasket is under it and I assume would have to be opened and a short pipe passed through to the space underneath. Thanks for your help.

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If it's not "sludged up" there is an open area between the gasket and bottom of the front part of the manifold where the vent is located. The intended flow path is from the valve chamber up thru a hole in the front part of the gasket, back thru the shelf area between the manifold and gasket to the vent. The vent hole in the manifold is directly over the edge of the block casting so there's a relief in the bottom of the manifold from the vent towards the center. This shelf area is really prone to sludge build up with the original set up. Even the air chamber the vent tube feeds in the air cleaner can get stopped up or restricted, reducing the effectiveness of the original system. It's probably best to remove the manifold to clean this area altho I have had luck using a flexible wire working it forward thru the vent hole to clear a path to the hole in the gasket. Judicious use of compressed air might also be of help.

You can see the "relief" around the vent hole near the bottom of the pic on the right.

post-31684-143138187259_thumb.jpg

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Thanks for the pictures and the explanation. Perhaps this car had a vent tube connecting the vent to the air cleaner, but I have not seen it. There seems to be no place to connect a tube to the air cleaner either. This engine had a complete rebuild not long ago so there isn't likely much sludge in the space between the manifold and the gasket, but maybe I should pull the manifold to check and also straighten the oil level rod which got bent during the previous pull to sort out the oil pressure issue.

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This not a very good pic but it does show the stock vent set up. There's a sleeve and clamp on the bottom of the aircleaner that the vent tube attaches. This is for the regular Lincoln not the Continental.

post-31684-143138187304_thumb.jpg

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  • 1 month later...

I've always heard that the PCV should be hooked up to carburetor vacuum, not manifold vacuum. You want the crankcase gasses to enter the intake at higher engine speeds, not at idle. But if its working, why change?

Abe

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PCV valves are self regulating.. Whenever the vacuum is high they restrict themslves to minimum flow. When the vacuum starts dropping on acceleration or when the engine is under load the PCV valve opens and draws off fumes. The vacuum port is fairly close to the carb so it should work ok.

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