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'41 Fat Bottom Girl

Replacing Breather Down Tube with a PCV Valve Setup

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I don't know if this is the right way to do this (still learning about the forum), but I thought it would be of interest to start a new topic about PCV valves. These are excerpts from a previous subject "Old Flatheads and Today's Gas". My thanx to James_Douglas and Adam H for raising the topic, I didn't find anything on previous threads and I am really curious if anyone has recommendations...
 
Comment from James_Douglas
7. I just set up a PCV after running the new engine for 15 years and 60K miles. The oil stays cleaner longer and there is no visible blow by at stop signs!
Question from Adam H P15 D30

James - 

Do you have a picture of your PCV set up?  I found mine sucks a little oil on long decels.  My engine is fairly fresh with good compression, I am probably going back to the draft tube....

Questions/ comments from me:

I was thinking of getting rid of my draft tube also when I do my rebuild. I anticipate some oil in my future PCV tube because of the usual minor drip I had from the crankcase down tube with past and current flatheads. Always seem to have a bit of blow-by no matter the engine condition.

I was thinking of fitting a crankcase filter screen (Dorman #47064 and Motorcraft FA1068 are a couple available) between the draft tube (stubbed out raised up in vertical position as Adam has in his photo) and the PCV valve. To contain the filter in some sort of housing I would have to get creative with a piece of suitable I.D. rubber tubing and fittings both ends to attach PCV hose, or do something like that. 

Another thought I had was an oil separator (Steeda makes one for Mustangs I was thinking of) and put it in the line between the PCV valve and carb base. I suppose the possible advantage with  that is it visible whereas thescreen at the draft tube would not (for maintenance?)

I will have to look on this forum to see if there are any posts on the subject.

If not, maybe some of the members have had some preventative fixes. Interesting you brought that up!

Great stuff...

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our search engine has evolved over the years and today has a return similar to google and is not as clear and concise.  You have to tweak your search words and syntax to get a good clean applicable list of threads.   There are eight pages of threads on the PCV subject....

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I tried searching for "pcv" and nothing comes up. I also tried searching for posts on putting a t5 trans behind a flathead by searching "T5" and got virtually nothing. What am I doing wrong? I've been using the "search" box at the top right hand corner of the page. Thanks for any help.

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Hi 40plyguy,

I'm pretty new to the forum myself...Per Plymouthy Adam's suggestions, I tried related words and had success.

I found if I went to "downloads" and entered "crankcase " in the search window, I found threads about adding PCV valves (mixed in with other crankcase stuff, but I did find PCV info going through those pages).

Haven't looked for info converting to a T5 tranny though...

Good Luck!

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I put a pcv valve on mine and it seems to be drawing a lot of oil also but the engine has over 60k on it and uses a little oil. Getting a 230 ready to put in it and will try the pcv valve on it.

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"The Oil Soup"- what a great handle! I had to chuckle...

From the threads (thanx again, Plymouthy Adams) when I do my PCV valve setup:

I will go from a hose fitting on a non-vented oil filler cap on the filler tube to a brazed fitting at the bottom of my oil bath air filter- giving me filtered air to the filler tube. 

Then will do a setup similar to Adam H P15 D30 with a vertically oriented stubbed-out downdraft tube with a hose fitting.

Will go from that to a PCV valve and then into the intake manifold.

What I am going to try in addition to these setups as described in the threads is an oil separator immediately before the PCV valve inlet. Per Steeda (tm):

They Connect to the PCV hose to prevent oil and crankcase vapors from getting into the intake manifold and decreasing your fuel octane. They are fully sealed to ensure no vacuum leaks, and are simple to service. They hold up to three ounces of fluid for service intervals lapsing each oil change. Includes hardware for installation.

Steeda's oil separator kits reduce detonation, oil burning and deposits on the valves by removing oil drawn through the PCV system before it can contaminate the intake charge.

This is why I was interested to try one. Hoping to limit oil/vapors getting into the intake, cleaner smell while running, and side benefit of no visible downdraft tube blow-by.  

So then I would have a "closed" PCV system with the possible advantage of a separator to trap unwanted oil into my intake.

Looking at doing my rebuild later this summer on my 80k miles flathead 6, and if I find any interesting results (positive or negative) using a separator I will post them. Maybe somebody in the forum has tried one already, but I didn't find it in the threads I found.

 

 

 

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I used a PCV from:

 

http://mewagner.com/?p=444

 

Great people to work with. Good product and good support.

 

I used a Drafting Tube Filter which was a MOPAR accessory to stop oil dripping down the drafting tube onto your garage floor.  One can also just cut the drafting tube and leave an inch or two on it as well.

 

ebay number: 142591711656

 

I then ordered a chemical silicon plug and some bendable aluminum tubing from McMaster Carr online:

 

Item Number: 9277K95 and   5177K72

 

I also purchased a Moroso Oil Separator :

 

https://www.jegs.com/i/Moroso/710/85497/10002/-1

 

..and a few fittings from my stash.

 

What I did was to take the filer out of the drafting tube filter first, you could just cut all but an inch or two off of a drafting tube and put a couple of slits in the tube wall so you can later use a hose clamp on it..

 

Then drill a hole in the silicon plug so the aluminum tube fits into to it tight. Glue the plug into the tube or filter housing.

 

Then cut and bend some aluminum tube to route the system where you want and to clear the exhaust manifolds. On mine, I ran it up to the fire wall just to the right of the hood hinge next to where the heater gets its hot water on a Desoto. Then stick it into the plug and put a little silicon on the outside to "hold" it and seal any vacuum leaks. Clamp the now short drafting tube (or the ebay one) to squeeze the plug onto the aluminum pipe.

 

Then I attached it via some vacuum hose to a bib on the Moroso oil separator input side. I then cut a very short section of hose on the output side and attached that to the PCV.

 

Then the output of the PCV runs down to the nipple on the base of the intake manifold below the carburetor.

 

I will get a couple of photo's if you wish in the next day or two and post them.

 

So the path is like this:

 

Air Intake on Side of Block at drafting tube mount >>> Oil Separator >>> PCV >>> Intake manifold.

 

One thing to keep in mind is that a PCV system is nothing but a controlled vacuum leak.  Depending on engine and carburetor jetting, you MAY have to increase the size of the Carter BB main jet so that the engine does not run lean.

 

You will have to re-set the idle mixture after you go through the multi step Wagner procedure to "tune" your PCV to you particular engine. It stopped all my blow by and the engine oil is staying much cleaner longer.  Also, my plugs look 'just a shade' lean and I am keeping my eyes on it and may go up one size on the main jets.

 

I get about a teaspoon of oil every months so far.  What is interesting is I am getting about 2 to 3 tablespoons of water out.  I also some folks at the US Energy Department that deal with fuels about how much water vapor does one get from blow by from the fuel with Ethanol. They really did not know. I winder if in older engines with a PCV, and not in warm places in the country, if fuel blow by with the newer ethanol fuel is depositing water vapor in the oil. I could also have a weeping head gasket as well, but the plugs do not have any tell tail "rust red" on the porcelain that one often sees with head gasket leaks.

 

Have fun,  James.

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Super- That sure sounds like the way to go. Excellent write-up explaining what you did, and your findings certainly give credence to the oil separator addition. I am looking forward to making the changes.

Thanx very much for taking the time to detail your set-up and the results. Great stuff!

 

 

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1 hour ago, The Oil Soup said:

Would it make any difference to run the pcv output to the air cleaner? Seems like that eliminates any negative effect on engine vacuum.

PCV is basically a "controlled" vacuum leak with backfire protection.  It requires manifold vacuum to operate properly.

This brings up another topic, with the low HP of these engines, what is the average vacuum reading at freeway speeds, 55-70 MPH?  I have never checked but if it's low especially pulling a long grade, might be better off with the draft tube???  Engine will have low vacuum when there is the most blow by where the draft tube will be functioning well because of the road speed.  Cruising around town probably wouldn't be an issue.  

 

Adam

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On 5/20/2019 at 10:45 AM, Adam H P15 D30 said:

PCV is basically a "controlled" vacuum leak with backfire protection.  It requires manifold vacuum to operate properly.

This brings up another topic, with the low HP of these engines, what is the average vacuum reading at freeway speeds, 55-70 MPH?  I have never checked but if it's low especially pulling a long grade, might be better off with the draft tube???  Engine will have low vacuum when there is the most blow by where the draft tube will be functioning well because of the road speed.  Cruising around town probably wouldn't be an issue.  

 

Adam

The vacuum spec is listed in most PCV makers catalogs, some are noted in the packaging.  When I get to that point, I'll check my vacuum at cruise and select appropriately

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On 5/20/2019 at 10:45 AM, Adam H P15 D30 said:

PCV is basically a "controlled" vacuum leak with backfire protection.  It requires manifold vacuum to operate properly.

This brings up another topic, with the low HP of these engines, what is the average vacuum reading at freeway speeds, 55-70 MPH?  I have never checked but if it's low especially pulling a long grade, might be better off with the draft tube???  Engine will have low vacuum when there is the most blow by where the draft tube will be functioning well because of the road speed.  Cruising around town probably wouldn't be an issue.  

 

Adam

High vacuum at idle restricts the flow.  Lower vacuum (lower varies by valve application) opens the passage.  So, on the road, under load, is when the PCV circuit is most effective.  Even with single digit vacuum levels, a lot of air will flow, again dependent on the valve you choose.

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22 minutes ago, kencombs said:

High vacuum at idle restricts the flow.  Lower vacuum (lower varies by valve application) opens the passage.  So, on the road, under load, is when the PCV circuit is most effective.  Even with single digit vacuum levels, a lot of air will flow, again dependent on the valve you choose.

Ken,

Exactly right!  I guessed on my PCV valve and the results are less than spectacular...  When you guess like I did, you get mixed results.

Maybe the cost of the PCV James mentioned isn't so bad, can tune for any scenario?

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Choose a PCV valve from engine with similar displacement, and it should work with no problems. To avoid burning oil, the valve should be placed high above sump, and connecting tube below the valve filled with steel wool.

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33 minutes ago, sser2 said:

Choose a PCV valve from engine with similar displacement, and it should work with no problems. To avoid burning oil, the valve should be placed high above sump, and connecting tube below the valve filled with steel wool.

That's how I chose my PCV valve and my guess was wrong.

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How about the pcv valve that vpw sells just for mopar flat 6,s.

 

DJ

 

 

Screenshot (35) VPW pcv valve.png

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3 hours ago, Adam H P15 D30 said:

That's how I chose my PCV valve and my guess was wrong.

Adam - what was particularly wrong?

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Some time ago I posted a topic about soviet copy of Flathead six, which then turned to OHV 4 etc. In one of improvements, it was equipped with enclosed crankcase, without PCV. The oil filling tube was simply elongated, and then, via rubber hose, connected to air filter, to the "filtered" side. The breather was also connected to air filter, but to "non - filtered" side. 

It's probably the simplest way of removing fumes from underneeth the car. Noone ever complained about it; I've never heard of problems with sucking oil out of engine or backfire problems, even though many of these cars ran on very low quality LPG instalations.

And that's how it looked like:

DSC_7875.JPG

image;s=644x461

3-1.jpg

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3 hours ago, sser2 said:

Adam - what was particularly wrong?

Just sucks a little oil on long decels. After reading through all these it might just be a flaw in my design but the draft tube rarely dripped oil, who knows. Also the breather on the drivers side seems to be doing more “breathing” during a long freeway drive at speed. ~70 mph. Never did this before the PCV mod. Compression is good, fairly fresh rebuild. 

Edited by Adam H P15 D30

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Thanks. Looking at PCV arrangement in modern cars, I see deflection baffles and oil traps to capture larger oil droplets. I am not a fan of draft tube. The bulkhead and floor panels are not exactly airtight, so cabin gets a whiff of crankcase gas coming out of draft tube. That nostalgic smell of old cars that I'd rather not have.

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6 hours ago, sser2 said:

Thanks. Looking at PCV arrangement in modern cars, I see deflection baffles and oil traps to capture larger oil droplets. I am not a fan of draft tube. The bulkhead and floor panels are not exactly airtight, so cabin gets a whiff of crankcase gas coming out of draft tube. That nostalgic smell of old cars that I'd rather not have.

That's part of the "charm" 😀

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