L6 226 Engine Question on PCV valve

captainlance

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Jul 22, 2017
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I have a 226 that has incomplete PCV components on it. In referring to the factory sheet about adding the kit to an engie, it mentions in para. 1, "Remove oil cap and replace with the supplied one".

As the original cap is an open system cap, running the engine with the pcv components installed results in nearly ZERO vacuum, and the engine does not want to idle, as the fuel flow is negligible.

The pcv valve I am ujsing is a AC-Delco, CV698, the screw in type. Looks very similar to the early MB / GPW type pcv.

Any ideas or idea of what oil cap to use? No interchange catalog I've found lists any.
 

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Seabee

Precision Fit
Dec 23, 2014
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Sorry Lance, I've never seen a PCV on a 226. Maybe a non-ventilated fill pipe cap that has a hole in the center for the valve to reside in?
 

MMB2N

Bigger Hammer
Jan 27, 2014
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Early 60's Chevy smallblocks have an oil fill tube that presses into the intake manifold and is the same diameter as the 226 tube. I'm sure you're aware that all the early PCV systems were the open style.
 

captainlance

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Early 60's Chevy smallblocks have an oil fill tube that presses into the intake manifold and is the same diameter as the 226 tube. I'm sure you're aware that all the early PCV systems were the open style.
I understand that, but why would they tell you to discard the original cap and use the one provided, that has a different part#? And whydoes all the vacuum disappear with the PCV valve in place?
 

mickeykelley

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I was beginning to wonder Lance if you ever did this. You know the F134 in my CJ5 has the PCV setup. The oil fill tube also is the dip stick and it fits loose so air will flow. Wonder if you tried something like that.

Oh, and Lance can you add PCV to the thread title so it comes up in searches since this is what it’s really about.

I'm watching this as I would really like to get rid of that draft tube and the oil mess it creates.
 
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MMB2N

Bigger Hammer
Jan 27, 2014
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I can't comment on the cap having never seen the one in the kit. If the PCV system is reducing vacuum as you indicate perhaps some kind of variable restriction in the line will be required to achieve a more optimal rate of flow.
 

WA7OPY

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NO, yours is way better, I remember seeing caps that had no horse hair and all the vents were gone, so the engine was non vented, so the pcv would work, also there was a orface in the vac line so the vac would not drop to zero...Phil
 

Herk

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Stepping back and looking at the big picture, you would want the oil fill cap to admit air. The PCV system cannot function without a means of fresh (preferably filtered) air into the crankcase to replace the vapor laden air drawn into the intake manifold. Since most of the 226 oil filler caps have a metal gauze "filter" they should do fine, at least from a functionality standpoint. The only PCV equipped 226 I have seen in the flesh struck me as having F4-134 parts in place of the road draft tube. My only guess would be that the replacement cap had diminished airflow so the crankcase operated at a slight negative pressure. I suspect if this were the case it was to avoid having to re-jet the carb more than anything. Even then, I suspect the overall difference would have been slight. Perhaps it was because many oil filler cap vendors had been used both for production and aftermarket replacements, so the only way to be sure it was compatible was to supply a replacement with the kit. As long at it lets air in, it will work.
 

captainlance

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Jul 22, 2017
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PHOTOS ADDED TO ORIGINAL POSTING PLUS....
I managed to get an original wwll pcv valve, (A-6895) the valve opens at 7.5" HG. As measured on a reliable vacuum pump. The replacement type GM- Delco valve, is always open, thusly kiling any possibility of maintaining a vacuum in the manifold and allowing the carburetor to pass fuel at idle. This is why after being on throttle, and returning to idle, the car runs afew seconds and dies.
I think some work on the valve to tighten the spring will bring me closer to a usable performace level.
 

captainlance

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My guess is the replacement cap was unvented...Phil
I was kind of leaning that way, or maybe with a very small hole to allow some air in. Many "Original" PCV systems were open, later ones are fully closed, like vehicles from the late 60's thru new cars today.
Lance..(N2hba)
 

mickeykelley

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I looked at my '58 CJ5 F134 that has the PCV and see that the oil dip stick tube is not really sealed and it has the tube that comes from the oil bath to the top of that dip stick/oil filler. Not sure just how much that opens the system.
 

captainlance

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MORE INVESTIGATION
Today I decided to get scientific, well, sort of. I reinstalled the A6895 PCV valve and jury-rigged a test hookup to allow me to check the vacuum while the engine ran. First, I took out the old reliable Snap-On scope and rechecked the engine, dwell, timing, advance, etc. All okay.
Then, I started the engine and checked the resultant vacuum at the mainfold, as shown. With the pcv hooked up, I only had 3.5" HG. of vacuum, certainly not enough to allow for advance nor fuel flow at idle. That is my stalling problem. With the pcv NOT hooked up, I have 13" HG. Perfect!
Constricting the rubber tube , to allow the vacuum to increase to 10" HG., the engine picked up speed and ran much better, with no stalling. Then, I removed the oil filler cap and put a rubber plug in the tube, to mimic a closed PCV system. This made NO difference at all. No vacuum increase.
The next thing, after one more possible PCV valve number I have to try, is to make a constrictor insert, from aluminum rod, with a drilled out hole for the suction line, to adjust the vacuum that way.
Onward!
The rear seat came back from the upholstery shop, l,ooks fabulous. We installed it and admired the look. Now, the headliner will be the next big job, after the pcv is conquered.Willys, pcv 9 18 001.JPG
 

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Seabee

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Dec 23, 2014
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13" of vacuum seems really low. Are you sure your damper isn't lying to you with it's timing mark location? You might try advancing your timing to get highest vacuum and then back it off 1/2 to 1" of vacuum.
 

jfcroni

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I have the original PCV setup that was installed (apparently) by a dealer. It's the one that was added with a TSB at some point. So I have all the parts including the original valve. No matter what I did, I could not get rid of the hesitation - advance timing, retard timing, change idle set, adjust fuel mix etc. I did get close once, but then I had preignition. When I look at the setup, I can see the route from the manifold (essentially opening a massive vacuum leak) is certainly going to screw with the fuel mixture system. At the same time, trying to restrict the ventilation system by plugging the oil fill will/can pressurize the crankcase...possibly leading to oil blowing out the oil seals or worse. So, it's like the PCV needs two circuits - one for idle and one for run that allows vacuum to stay higher at idle and more flow at run. It seems to me that a more metered PCV is the answer. I used one by ME Wagner.... It was the most expensive PCV valve I ever bought, but I'm very happy with the results.

I think there is also some wisdom out there about mounting the valves vertically vs horizontally.
 

Stakebed

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At the same time, trying to restrict the ventilation system by plugging the oil fill will/can pressurize the crankcase...possibly leading to oil blowing out the oil seals or worse.
I think the opposite occurs. With a PCV system plugged into the "valve cover" and connected to vacuum, without a method for introducing air into the crankcase, the oil pan will get sucked inward and the gaskets/seals get sucked in. Essentially, without crankcase ventilation, a vacuum would be created inside the engine.
 

mickeykelley

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So I keep coming back to the F134. How does it work correctly. The PCV is horizontal, and it feeds from the valve cover and goes to the base by the carb.

8D2BC0F8-63FC-438E-A9F4-CAB51B259ABD.jpeg
15C5F8F1-1874-49B0-BD6B-909A94128463.jpeg
 
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Jmh24

Bigger Hammer
Feb 1, 2015
49
Wisconsin
First Name
Joe
Willys Model
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Willys Year:
1960
MORE INVESTIGATION
Today I decided to get scientific, well, sort of. I reinstalled the A6895 PCV valve and jury-rigged a test hookup to allow me to check the vacuum while the engine ran. First, I took out the old reliable Snap-On scope and rechecked the engine, dwell, timing, advance, etc. All okay.
Then, I started the engine and checked the resultant vacuum at the mainfold, as shown. With the pcv hooked up, I only had 3.5" HG. of vacuum, certainly not enough to allow for advance nor fuel flow at idle. That is my stalling problem. With the pcv NOT hooked up, I have 13" HG. Perfect!
Constricting the rubber tube , to allow the vacuum to increase to 10" HG., the engine picked up speed and ran much better, with no stalling. Then, I removed the oil filler cap and put a rubber plug in the tube, to mimic a closed PCV system. This made NO difference at all. No vacuum increase.
The next thing, after one more possible PCV valve number I have to try, is to make a constrictor insert, from aluminum rod, with a drilled out hole for the suction line, to adjust the vacuum that way.
Onward!
The rear seat came back from the upholstery shop, l,ooks fabulous. We installed it and admired the look. Now, the headliner will be the next big job, after the pcv is conquered.View attachment 83033
Captain Lance,
As I see your photo, if the hose off the top of the tee is going to your vacuum gauge, it is between the pcv valve and the valve cover, therefore the gauge reading is your crankcase pressure not the manifold pressure. You may want to put the tee directly into the manifold, and the pcv valve into one leg of the tee. Then the other leg of the tee will be measuring manifold pressure.
Hope this helps,
Joe
 
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