PCV valve on a 239
 

I read on this forum, a number of years ago, about someone building a positive crankcase ventilating system for a flathead V8. I did a search for info and came up empty handed. Has anybody done this? If at all possible I would like to do this to my flathead.

The link below may be of interest

MOTOR, Flathead PCV - THE H.A.M.B.

ALBUQ F-1 (Ross) made up a simple pcv for under $10. pics in this thread:https://www.ford-trucks.com/forums/6...or-an-8ba.html

That one that Ross did was a great idea and looks proper.

Now just in case any of you who have a multiple carb intake, you will see there is no Road Draft Port Hole.

So Under the Manifold where the pipe comes up to meet the stock Road Draft Port Hole, you can drill a hole and thread it and use a screw in Chrysler 4-6 Cly PCV. Then run a hose from that to your vacum source on the intake.

You will have to cut off a short piece of the pipe that comes up to meet the Stock Road Draft Port Hole.

I have done this on a 2 Carb intake on an Offenhauser Intake. Also if using a Close 2 Carb Intake, make sure the front of the Manifold lines up with the the Fan Pulley, if your going to use a Stock Geneator. Some are offset and your Gen., won't line up.:-X22

I've been playing with the setup I did earlier. I think the holes in the manifold wiper connection, that are inside the outer hole and go to the actual throttle bores, need to be opened up to 1/8" for best results.

You can't run vacuum wipers off the same connection.

Ross, I posted here awhile ago regarding a cure for the vacum wipers, and that was a reserve tank.

That is the old type oil filter can, use it for a vacum reserve tank. Of course you wouldn't be able to use it as an oil dilter any longer, but if you had one and wanted it to look stock there is the answer.:-X22

I remember your filter/vac can, very clever! I measured my vacuum at idle with the PCV, and it was really low, like 4", because the PCV is bleeding in more air than the passages can flow. That's why I opened up the passages.

I need manifold vacuum for my distributor and am going to add a separate connection for that. If I were running vacuum wipers, I'd do the same (with a vac can and check valve).

Thanks for all the info guys! Good ideas. I like the one about using the oil filter can as a vacuum reservoir. I am adding a full flow filter, on the frame rails, and leaving the original can on just for looks.
I see another question identical to mine and I like the idea of concealing the PCV valve under the manifold. Although my manifold is already installed I think it is worth it to remove it and make the necessary mods.
Are there any considerations such as flow I should concern myself with? Why couldn't I just drill & tap a hole, 1/4" NPT, in the bottom of one of the runners and screw the valve in there and just let it pull vapors from the lifter valley? Of course plugging the road draft tube too.

You want to preserve the Ford concept of air flow inside the crankcase, so you want to suck out of the tube that comes up the front of the block. Then you want all the cylinders to share the vapors, to avoid fouling mostly. If you're using a stock manifold, hitting one of the main runners that serves 4 cylinders, near the middle of the engine (front to rear) should be OK.

Make sure you don't drill into the exhaust heat riser passages that go under the carb!

Another thought Ross, did you seal off your oil fill breather? I have some work I have to do early in the week so I'll try & get my manifold removed later in the week.

My work failed to materialize today so I and some time to build my PCV valve setup. Here is what I ended up with:

That's an interesting concept. I would have a concern with the rubber hose deteriorating in the constant vapor environment of the insides of the engine, though. Other than that, I'll be interested to see your report on how it works in a few months.

You don't want to seal up the breather on the oil filler cap. That's where the fresh air comes in so the road draft tube or PCV valve can pull out the dirty air. It needs to be open with a clean filter mesh.

Great job, Steve! Wayne is right, the breather cap both lets in fresh air, and also lets crankcase vapors out under heavy load when there isn't enough vacuum to suck in all the vapors thru the PCV. Strictly speaking, a filter for the cap is a good idea, the steel wool in the stock cap doesn't stop much dirt. OEM systems run that to the air cleaner, outside the filter element (those crescent-shaped little filters that snap into the housing). If you ran a hose from the fill tube to the air cleaner, then you could tightly cap the fill tube.

As long as the hose is made for oil service it should be OK; it kind of looks like heater hose?

I suppose it's obvious, but you'll need to put the intake gasket on before installing your plumbing. I've had my intake off 4 times this summer, a good tip is to make up some long studs, one at the front and one at the rear, so you can drop the manifold straight down in the correct location. They aren't light!

Autoparts stores sold a kit to install PCV device on 239 flatties, why?

At one time, CA smog checked all 1950 and newer vehicles, all had to have PCV installed. Since no FoMoCo product came with PCV prior to 1961, autoparts stores did a "land office business" selling these devices to PO'd CA owners.

I thought I'd throw this out there for anyone else who is contemplating adding PCV. I have a Canadian aluminum manifold off a big truck, that has an additional vacuum port that is much bigger than the one for wipers. I believe it was for vacuum-assisted brakes. It would be perfect for PCV. After comparing it to my cast iron manifold, I believe (have not yet confirmed) that an iron manifold could be drilled similarly.

It's drilled and tapped 3/8"-NPT, with holes drilled at an angle into each throttle bore at 3/16". It would be kind of hard to drill a shallow hole and tap it, almost certainly would require a bottoming tap. Maybe you could cut down a regular tap.