PCV conversion

[38plymouth]

I'm trying to figure out an easy way to convert my 38 from the road draft tube to a pcv system. The only place that I can find that has a vacuum source (without drilling something) is in the manifold just below the carb where the vacuum wipers hook up. Would this be enough vacuum to work if I replaced the fitting with a "T". It looks like it's about 3/8's. It would be simple to do if this spot works and I don't think many people would notice it was done.

[Don Coatney]

A "T" in the wiper vacuum connection will work. Have you seen the PCV information in the link below?

http://www40.addr.com/~merc583/mopar/framesets/softwareframeset.html

[38plymouth]

I did, and I also just noticed that it looks like the exact same spot that I am interested in. Stupid me.

[billwillard]

The only stupid guestion is one that never gets ask.

[aero3113]

I used a T fitting with mine and it works great.I bought the pcv valve and adaptor from Vintage Power Wagons and some fittings from Ace Hardware.If you want me to post some pics. e-mail me and I will send them to you.

[38plymouth]

I did the PCV conversion yesterday, it was really simple and cost about $12. I had a rubber grommet and a pcv valve in my stash of junk. The grommet fit into the hole in the block perfect and I used a little silicone to hold it in. I bought a few fittings to make a tee. The only thing I didn't like was the idle got real rough with the pcv valve setup. I went to napa and bought new pcv valve that had a tighter plunger inside. That helped but the idle is still a little rough. It smooths right out if I pinch off the hose. I don't think I mind the rougher idle though, it sounds pretty good with dual exhaust and glasspacks.

[martybose]

Did you close off the bottom of the oil filler cap? If not, you just introduced a rather large air leak into your intake manifold.

Marty

[38plymouth]

I thought I needed the opening in the cap so it would suck in clean air. If you close it off where does the air enter the engine?

[Normspeed]

I think it relies on the available blowby in the crankcase. We used to install an AC kit in the 60's if I can remember correctly, there was a big rubber plug that went in the downdraft tube to block it off, and a sealed type oil filler cap, with a hose nipple. that hose went to the intake, and had an inline pcv valve.

[billwillard]

You DO NOT want to close off your incomming air. If you do you will have oil leaks. When this was done it was replaced by a tube running from the filler tube to the air cleaner but no need to do that. Go to the parts house and get a pvc valve for a 3.8 (or some where in that range) engine and your car should idle better. Too large a pvc valve and you will have a rough idle. Too much vacum lose.

[38plymouth]

I tried buying a pcv valve for a 6 cylinder at napa. Unfortunately the current employees there don't think you can look up anything unless it's on the computer. When I worked there we looked up parts in the books and we went by dimensions, etc. for guys working on old stuff. The best they would do was hand me the box of valves. I picked the one with the tightest spring inside.

One thing I don't understand is I pulled the oil fill cap off and plugged the opening with my hand. I thought that would seal the vacuum and I would notice a difference in the idle, it didn't make a difference at all.

[Normspeed]

Bill, I think the whole idea is for engine vacuum to create a suction effect that flows crankcase gases into the intake for reburning. PCV=Positive Crankcase Ventilation. If it's working right there should be no pressure in the crankcase to cause leaks, only a slight suction. On an older Volvo I had, the test for properly operating pCV was to unscrew the oil filler cap and set it on the hole with the motor running. If the cap was pulled down and held by suction, it was all working ok.

But heck, I've been wrong before:D Lotsa times.

[Suddensix]

I have a 53 Ford pick-up with a 68 302 Ford engine. The PCV system is stock and has an open oil filler cap. Therefore I have set up the one on my 218 the same. Haven't had it running yet so time will tell. Used the PCV valve out of a Dodge Shadow and some plumbing parts from the hardware store to make the system for the 218, cost about $10.00. This method was described on the forum awhile back.

[Powerhouse]

I did a similar thing and used the stock oil breather...runs great!

[38plymouth]

I never did post a follow up on what I did with mine. I was looking at the pcv valve all wrong. I ended up buying a valve with a light spring that closed when the engine idled, it stopped the vaccuum leak and it idles perfect now. As soon as I rev the engine a little the valve opens when vacuum drops and it sucks the fumes away. It was definately worth the time to do and it didn't cause any problems at all.

[grey beard]

You all got it right. Sudden Six, the only advantage in finding a cleanere aire source for PCV intake air is to keep things a little cleaner. I foujd a spring-loaded flap type oil fill cap that I used for my 218. It has a hose nipple on the side for excess blowby that I routed to the air cleaner. Now the air pulled into the crankcase by the PcV system is just a little cleaner than if it simply pulled ambient air from behind the fan blades.

Either way, a PCV sysrtem on our flatheads is an excellent option to help keep moisture and condensation from accumulating and creating sludge in these blocks. Wouldn't it be fun to look inside everyone's valve chamber who does NOT have a PCV system, just to see how much sludge has accumulated on those short runs we all like to take? Why, it's almost enough to make a fellow install a 180 degree thermosrat - that'd help a lot, too. JMHO:)

[Powerhouse]

Why would sealing off the air cause leaks???? I think I have this problem....

[greg g]

Question: How does attaching a hose to the oir cleaner provide air tot he crankcase??? It seems to me any holes you put into air cleaner are going to suck air whenthe engine is running. I recall on older car I had had a very basic system ther had a inlet breather on the valve rocker cover and a hose tot he air cleaner from the filler neck. The filler did not have a breather. So the flow of that system was in throung the valve cover and out throung the oil filler pipe, I assume the air passed through the oil return passages from the head ito the crank and then up an out the fill tube to the air cleaner. The isr cleaner fitting had a fiber pad on it to catch the chunks but any vapors etc got sucke throught he carb into the engine. I think manifold vacuum would be hard pressed to overcome the flow of air into and through the air cleaner. I would be at bes neautral and no air would flow either way.

[Powerhouse]

You all got it right. Sudden Six, the only advantage in finding a cleanere aire source for PCV intake air is to keep things a little cleaner. I foujd a spring-loaded flap type oil fill cap that I used for my 218. It has a hose nipple on the side for excess blowby that I routed to the air cleaner. Now the air pulled into the crankcase by the PcV system is just a little cleaner than if it simply pulled ambient air from behind the fan blades.

Either way, a PCV sysrtem on our flatheads is an excellent option to help keep moisture and condensation from accumulating and creating sludge in these blocks. Wouldn't it be fun to look inside everyone's valve chamber who does NOT have a PCV system, just to see how much sludge has accumulated on those short runs we all like to take? Why, it's almost enough to make a fellow install a 180 degree thermosrat - that'd help a lot, too. JMHO:)

Where does the hose from the oil fill cap go to in the carb air cleaner....behind the filter element(so it's getting sucked straight into the carb or outside the element so it has to go through the filter to get in the carb? WOuldn't tha create suction from both ends of the system?

My air cleaner is an aftermarket open air type...no oil or inlet pipes or anything. Should I rout a hose nipple outside of the air elemnt or inside the air cleaner element?

[TodFitch]

Why would sealing off the air cause leaks???? I think I have this problem....

The blow by past the rings needs to be able to get out of the crankcase. If the crankcase is sealed then blow by will pressurize the the case until something leaks.

Really old engines just had a vent to release the blow by.

The next step was a draft tube that used Venturi effect to pull a slight vacuum when the car is at speed and a source of filtered air (the oil soaked wire mesh in the filler cap) at the opposite side of the engine. This cross flow of clean air was to purge the blow by entirely out of the engine.

That was followed by an open PCV system. The source of fresh air was the same (oil filler cap) but the vacuum was now available at all road speeds.

But when an engine gets old, the blow by is too much for the PCV and some blow by comes out of the crankcase air filter (the oil filler cap). So the oil filler cap was made sealed and a hose was run to the carburetor air cleaner. This meant that you had one filter for air to the carburetor and to the crankcase. And if the blow by was more than the PCV system could handle the excess was fed into the top of the carburetor and burned that way.

[Powerhouse]

ok. I get it . DId the hose from the fill tube for venting the excess blowby go behind the air cleaner element or in front of it? If it went in front it would have to go through the air cleaner to get into the carb to reburn. If it went behind it it would go straight into the carb to burn....

On more modern cars I've seen the hose from the fill tube go to the air cleaner in front of the cleaner element...so it had to actually be sucked back in through the filter. I also saw one that had the same hose going behind the filter so it would just go right into the carb...no filteration.