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1939 201 cu. in. PCV Retrofit from 1960s 230 engine

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Just finished installing a pcv valve (AC CV-698C) from a 230 cu. in. military surplus (built in 1967) engine into my 1939 Plymouth pickup. I'm uncertain as too the exact year of my engine? Anyhow, after installing it, I needed to adjust the idle mixture. The engine seems to run slightly rougher at higher rpm (around 1500 or more) Any opinions on this?  Another question; is it OK to drive without the tube going to the air filter? I'll need to do some fabricating to do this. I plan on converting to a paper element filter as well. It's been my experience just about every time I modify something, it rarely goes smoothly. Has anyone made this modification and offer any wisdom?

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I ran mine like yours and it drew a lot of oil so I think it is better to plumb it to the air filter, unless there is some sort of mesh at the road draft fitting to catch oil mist. Do you have a filter at the oil breather cap?

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additional information - grey beard's PCV valve installation & modifications

 

You can run the partial PCV setup but it will not draw fumes from the crankcase during high vacuum operation; full PCV setup will draw fumes during all vacuum conditions. Routing of the PCV valve tubing should allow for any oil droplets to drain back into the crankcase to avoid puddling that could choke off that line, which could lead to fouling and eventual clogging :cool:

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2 hours ago, JBNeal said:

additional information - grey beard's PCV valve installation & modifications

 

You can run the partial PCV setup but it will not draw fumes from the crankcase during high vacuum operation; full PCV setup will draw fumes during all vacuum conditions. Routing of the PCV valve tubing should allow for any oil droplets to drain back into the crankcase to avoid puddling that could choke off that line, which could lead to fouling and eventual clogging :cool:

Thanks JBNeal! Very helpful. I read Grey Beards posts and it seems an identical issue to mine. I have not had my truck on the road since I added the pcv valve, but will in the next few days. Just seemed a bit of faltering when hold open the throttle in the shop.  I was also thinking of enlarging the main jet. I think I will add a tube to the air cleaner before I explore other pcv valves. The valve and plumbing came off a 230 cu. in. engine which had a Carter Ball & Ball ETW1 carburetor.  I'm not positive now what displacement my truck's engine was originally, but we did bore it over-size (over 30 years ago) so, I'm guessing around 220 cu.in? I wouldn't think that small of a displacement difference would affect it? I'm guessing that the carb on the 230 military engine was likely jetted larger?

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Let me put this question here as a lot of people will be reading about PCV :

 

I'm considering installing one but by plugging the road draft tube and connecting to the valve chambers.  The reasoning is that the valve chamber will have less oil splash to deal with and will still have access to the crankcase gases. 

 

I plan to use a valve that screws into either the intake under the carb, or a carb spacer under my two barrel.

 

 

Comments?  crazy idea or not?

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Since there is a port in the block for the draft tube, might as well use it...concerns about oil droplets getting sucked up into the charged air stream can be dealt with by dampening the air flow with metal mesh very much like that brillo pad filter media in the crankcase breather cap.  The intake manifold should have at least one vacuum port that can be used, or ya can tap the cast iron to make your own port.  Adding a carb spacer can be tricky as there should be a small vac.passage that is needed by the carb.

 

Not sure how the military carbs differ from the civilian carbs internally...I had communicated with grey beard about his PCV work and suggested choking down his crankcase air breather,  but he had dialed in his truck with the newer style PCV valve, was happy with his customization and wasn't interested in experimenting further...

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On 6/21/2020 at 12:42 AM, JBNeal said:

Since there is a port in the block for the draft tube, might as well use it...concerns about oil droplets getting sucked up into the charged air stream can be dealt with by dampening the air flow with metal mesh very much like that brillo pad filter media in the crankcase breather cap.  The intake manifold should have at least one vacuum port that can be used, or ya can tap the cast iron to make your own port.  Adding a carb spacer can be tricky as there should be a small vac.passage that is needed by the carb.

 

Not sure how the military carbs differ from the civilian carbs internally...I had communicated with grey beard about his PCV work and suggested choking down his crankcase air breather,  but he had dialed in his truck with the newer style PCV valve, was happy with his customization and wasn't interested in experimenting further...

Not sure what you mean about "a small vac.passage that is needed by the carb." I'm thinking of making a spacer between the carburetor and the air filter housing then attach a 1/4 NPT fitting. Attach a tube to it and the other end to the oil fill tube. This is what was on the military engine I have. I'm unaware of any vac. passages?

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There is more than one way to port into the charged air from the crankcase as indicated by the various drawings that I referenced for the original PCV kit, but there are basically 2 paths from the crankcase:  from the block, where the PCV valve is installed into the intake manifold; and from the oil fill tube, routed to the air cleaner housing.  It is my understanding that the air cleaner provides pressure relief from the crankcase to atmosphere to avoid causing any issues with the carburetor, providing a path of least resistance in case of excessive combustion chamber blowby.  Modern overhead valve engines just have a fitting on the side of the air cleaner to attach a hose from an intake valve cover (that is usually filtered), which could work on the oil bath air cleaner housing.   The two ways described in the download section aren't as easy to complete, both requiring brazing a nipple through a drilled hole on the bottom of the housing...one version has a nipple through the oil bath, which is just a more difficult way to do the fitting on the side of the housing; and the other nipple is through the base of the housing below the oil bath, at an angle, which requires quite a bit of finagling in a very small space with thin material to make work but is possible and bypasses the oil bath entirely.  I had an idea on how to make this work painlessly that would not require brazing but have been sidetracked something fierce for awhile now so I cannot conclusively say if it is worth the risk of damaging a working oil bath air cleaner that is not readily replaceable...adding a ported spacer to the top of the carb could work though :cool:

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As stated, it is a simple system, the valve itself being the most complicated.  It needs to close (or nearly so) at idle vacuum open its' max at cruise vacuum and close tightly in the case of an intake backfire.  Just be sure the air going into the crankcase is filtered.  the original oil filler did that for the road draft system, but crudely IMO, just a metal wool pad with oil on it.  Pulling from the filtered side of the carb air filter is ideal. 

 

As I mentioned in another post, my plan is to find a PCV valve that can be adjusted by changing or shimming springs.  A nice machined version is available, but way to expensive for my taste.  The military version on Power Wagons is fine for that application, but I'd bet the running vacuum on one of those is much higher than we will see on the highway at 60+, with an overdrive or higher speed differential.  That compared to the 5something:1 PW, at 45mph.   Higher load on our engines should = lower vacuum.

 

d.....IT,   I'm overthinkin' this again.

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11 hours ago, JBNeal said:

There is more than one way to port into the charged air from the crankcase as indicated by the various drawings that I referenced for the original PCV kit, but there are basically 2 paths from the crankcase:  from the block, where the PCV valve is installed into the intake manifold; and from the oil fill tube, routed to the air cleaner housing.  It is my understanding that the air cleaner provides pressure relief from the crankcase to atmosphere to avoid causing any issues with the carburetor, providing a path of least resistance in case of excessive combustion chamber blowby.  Modern overhead valve engines just have a fitting on the side of the air cleaner to attach a hose from an intake valve cover (that is usually filtered), which could work on the oil bath air cleaner housing.   The two ways described in the download section aren't as easy to complete, both requiring brazing a nipple through a drilled hole on the bottom of the housing...one version has a nipple through the oil bath, which is just a more difficult way to do the fitting on the side of the housing; and the other nipple is through the base of the housing below the oil bath, at an angle, which requires quite a bit of finagling in a very small space with thin material to make work but is possible and bypasses the oil bath entirely.  I had an idea on how to make this work painlessly that would not require brazing but have been sidetracked something fierce for awhile now so I cannot conclusively say if it is worth the risk of damaging a working oil bath air cleaner that is not readily replaceable...adding a ported spacer to the top of the carb could work though :cool:

 Here's some pics of what I'm attempting. Basically, I've just transplanted the system off the later model military engine. I'm in process of making an adapter between the carb and the air cleaner housing. It's almost done, but I need to silver solder the boss to my adapter and drill and tap for 1/4-NPT. image.png.dee025efe97d27135ac247c444ccf5a4.png I've also ordered a oil fill tube from vintagepowerwagons.com that already has a fitting and also a sealed oil fill cap. Once this is done, all I need to do is plumb them together. I hope! Lols!

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4 hours ago, kencombs said:

As stated, it is a simple system, the valve itself being the most complicated.  It needs to close (or nearly so) at idle vacuum open its' max at cruise vacuum and close tightly in the case of an intake backfire.  Just be sure the air going into the crankcase is filtered.  the original oil filler did that for the road draft system, but crudely IMO, just a metal wool pad with oil on it.  Pulling from the filtered side of the carb air filter is ideal. 

 

As I mentioned in another post, my plan is to find a PCV valve that can be adjusted by changing or shimming springs.  A nice machined version is available, but way to expensive for my taste.  The military version on Power Wagons is fine for that application, but I'd bet the running vacuum on one of those is much higher than we will see on the highway at 60+, with an overdrive or higher speed differential.  That compared to the 5something:1 PW, at 45mph.   Higher load on our engines should = lower vacuum.

 

d.....IT,   I'm overthinkin' this again.

Yeah Ken!  I overthink everything too. And, I also thought this should be a "simple system". But somehow, for me anyhow, these simple things always seem to get really complicated.  Lols!

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14 hours ago, PT81PlymouthPickup said:

 Here's some pics of what I'm attempting. Basically, I've just transplanted the system off the later model military engine. I'm in process of making an adapter between the carb and the air cleaner housing. It's almost done, but I need to silver solder the boss to my adapter and drill and tap for 1/4-NPT. image.png.dee025efe97d27135ac247c444ccf5a4.png I've also ordered a oil fill tube from vintagepowerwagons.com that already has a fitting and also a sealed oil fill cap. Once this is done, all I need to do is plumb them together. I hope! Lols!

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I really like that brass filter housing to carburetor adapter!  I currently have PVC that I machine to fit.  I just might have to find a some large brass tubing :)

 

Thanks,

 

Brad

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17 hours ago, PT81PlymouthPickup said:

Would have been a lot easier if I had tubing. I made it from a piece of round stock I had laying around. Lots of chips! The clamp came from McMaster Carr.

 

That would be a lot of chips :)

 

Thanks for the idea.

 

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Just in case anyone's interested, I finally finished plumbing my PCV retrofit. Here's some photos. Everything seems to be working well in my shop, but I still need to road test.

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The rough running engine may be due to a lean condition caused by the PCV using a source of vacuum to properly work. This creates an additional source for air to enter the combustion chamber around the carb intake and air filter directly from the crankcase.  I’ve made up 3 of these systems experimenting with different components on each.  Each one uses a shortenened and blocked off road draft tube with a nipple welded on attached to a vacuum hose.  I left the nipple pointing upward so that any accumulated vapor can drain back into the engine when not running.  The best working one uses a valve from a slant 6 which I chose due to it being a similar displacement of the flatties.  I t’d directly off the intake manifold as a vacuum source.  If you have vacuum wipers you’ll notice a difference in their performance because they now share their vac source w the PCV system.  It definitely keeps the oil cleaner than the old draft tube setup.

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2 hours ago, MBFowler said:

The rough running engine may be due to a lean condition caused by the PCV using a source of vacuum to properly work. This creates an additional source for air to enter the combustion chamber around the carb intake and air filter directly from the crankcase.  I’ve made up 3 of these systems experimenting with different components on each.  Each one uses a shortenened and blocked off road draft tube with a nipple welded on attached to a vacuum hose.  I left the nipple pointing upward so that any accumulated vapor can drain back into the engine when not running.  The best working one uses a valve from a slant 6 which I chose due to it being a similar displacement of the flatties.  I t’d directly off the intake manifold as a vacuum source.  If you have vacuum wipers you’ll notice a difference in their performance because they now share their vac source w the PCV system.  It definitely keeps the oil cleaner than the old draft tube setup.

During my endeavours to find why my engine was running a bit rough at mid rpms I discovered I had worn out distributor bushings and shaft. After replacing them it now runs smoothly. I took the truck out for an hour cruise yesterday and so far (knock on wood) it's running great.  I used basically the same PCV plumbing and valve that was on the 1960s military engine. I imagine it's the same as Vintagepowerwagon's sell? Anyhow, I'm not sure if the PCV system is working properly? At idle the valve clicks in and out if I disconnect it and hold my finger on and off it. I can't determine any vacuum at the oil filler tube. Seems like it should be a relatively simple system, but I still don't completely understand the nuances of how it works or how to check it? It looks pretty good though!  Lols!

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JBN thanks.  I just remembered I have an oil fill cap from a slant6 that has a factory nipple on it, and  an original air filter housing with the same setup.  My experiment continues!  As far as the PCV valve chattering, the one in my truck has done that for the last 39 years I’ve owned it.  Sure do miss owl’ Greybeard.  Spent some time w him and his brother at our truck show in Macungie PA years ago.  A walking encyclopedia of common sense!

 

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10 hours ago, JBNeal said:

Thanks JBN!  Very helpful.  It seems to me with PCV system installed and engine at idle we should be able to sense there is some vacuum on the crankcase just by holding your hand over the fill tube? I don't feel any at my fill tube? I tried this before I plumbed the fill tube to the air filter. I know it's pulling vacuum at the valve, because I've disconnected it several times and checked with my finger. I mean we have introduced vacuum to the crankcase and it seems substantial enough at the PCV valve. I don't believe there are enough leaks through seals that it should not be discernible at the fill tube? Am I missing something? Probably my simple minded thinking again which gets me in trouble often. Lols!  Now that I have corrected my distributor issue my engine is running smoothly throughout the rpm range. The PCV system I installed came off a 230 cid. engine which is probably pretty close in displacement as my earlier bored engine.

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5 hours ago, MBFowler said:

JBN thanks.  I just remembered I have an oil fill cap from a slant6 that has a factory nipple on it, and  an original air filter housing with the same setup.  My experiment continues!  As far as the PCV valve chattering, the one in my truck has done that for the last 39 years I’ve owned it.  Sure do miss owl’ Greybeard.  Spent some time w him and his brother at our truck show in Macungie PA years ago.  A walking encyclopedia of common sense!

 

Really stinks losing the experience and wisdom of old timers. Greybeard and now Don Coatney were wealth's of information on here. My father was one of those "walking encyclopedia" types whom I should have listened to more. He was brilliant even though he never finished high school. He joined the Navy during WW2. First crew aboard USS Midway CV41 where he learned aircraft hydraulics and then started an auto repair shop after the war which continued until his death. He learned and knew exactly how and why things worked and how to repair them. I keep my hand in mechanics just a bit to remember how difficult he and many of his generation had to work. Now I am an old timer :( And less wise than I once thought.

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21 minutes ago, PT81PlymouthPickup said:

 Now I am an old timer :( And less wise than I once thought.

 

THAT in-of-itself shows wisdom, we all at some point think we "know everything" and find out we don't. Accepting that we don't have ALL the answers is a huge step in growth and wisdom.

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PCV is basically a small vacuum leak, so you shouldn't feel a strong suction at the oil fill tube like ya would at the carburetor...this small vacuum leak is only trying to direct flow of the evaporative hydrocarbons in the crankcase into the charge air flow, taking any steam formed from heating up the crankcase oil with it...whatever oil mist created should be heavy enough to drain back into the crankcase if the PCV is plumbed adequately, tho some of it will get into the charge air flow...this small vacuum leak is also plumbed to a reservoir of sorts with the crankcase, which is then plumbed to atmosphere through the air filter, to allow for pressure relief...I imagine if'n ya put a piece of paper over the oil fill tube, you'd see some vacuum effects :cool:

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7 hours ago, PT81PlymouthPickup said:

Thanks JBN!  Very helpful.  It seems to me with PCV system installed and engine at idle we should be able to sense there is some vacuum on the crankcase just by holding your hand over the fill tube? I don't feel any at my fill tube? I tried this before I plumbed the fill tube to the air filter. I know it's pulling vacuum at the valve, because I've disconnected it several times and checked with my finger. I mean we have introduced vacuum to the crankcase and it seems substantial enough at the PCV valve. I don't believe there are enough leaks through seals that it should not be discernible at the fill tube? Am I missing something? Probably my simple minded thinking again which gets me in trouble often. Lols!  Now that I have corrected my distributor issue my engine is running smoothly throughout the rpm range. The PCV system I installed came off a 230 cid. engine which is probably pretty close in displacement as my earlier bored engine.

If the PCV valve selected is near a perfect match for the engine's vacuum characteristics, there will be no, or nearly no, air flow through the system at idle. Little flow, certainly not enough to create a vacuum in the big old crankcase.  The valve is to be closed, or nearly so,  at idle vacuum and open at normal cruise vacuum.  An open valve at idle would ruin the idle of the engine, way to much air to blend with the little idle fuel passages.   And, there is, or should be, very little blowby to evacuate from the crankcase at idle anyway.  Under load and resultant high combustion chamber/cylinder pressure is where the PCV system is needed. 

 

I would like an adjustable valve for my engine, but the only one I know of is well north of 100 bucks.  I'll try to fab up an adjustable version one day, maybe.

Edited by kencombs

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