Chevy G506 PCV and valve covers

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forestry4evr
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Chevy G506 PCV and valve covers

Post by forestry4evr » Thu Aug 10, 2017 2:52 am

Hey all,

The text below contains "deep in the weeds" technical minutia and esoteric musings that few will most likely care about...if you are one of those individuals, read no farther...you have been warned. If you have interest about the evolution of the crankcase ventilation systems in the five year production period of Chevy production, read on...

Not long ago, a fellow G506 enthusiast and I had a conversation about the innovation of Positive Crankcase Ventilation (PCV) systems and internal combustion engines. I had recently read somewhere on another civilian vehicle forum that there was a claim that PCV systems came into being at about or slightly before the era of emission controlled engines. Immediately my mind recalled the components I have from a late 1942 truck that had the remnants of a PCV system. Although GM was not alone in using the technology back in the 1940's, this thread is centric to Chevys as they are what I know.

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First of all, this is based on reference material gleaned from technical manuals and parts manuals. As with anything, your first step should be consultation with your TM9-805.

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In the 1943 publication, the PCV system is clearly addressed

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Since the early 1941-42 trucks did not have the PCV system, there must be some evidence of different valve covers available through the production years.

From physical observations and literature, it became evident that there were actually 3 different crankcase ventilation systems employed during the 1941-1945 production period.

The first ventilation system employed on the early 1941 trucks (some of these models were actually assembled in 1940 primarily for the Lend-Lease program), consisted of a very rudimentary ventilation system having only slots cut into the valve cover much like the civilian 216 cousin.

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Note the small ventilation slots cut into the valve cover.

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This the same valve cover as above. Note the absence of any other breather on this era valve cover.

The second ventilation system was used on the late 1941 ZP and early N series trucks until sometime late in 1942. This method eliminated the slots in the valve covers as they were obviously a source for dirt/dust/water contaminants encountered on Chevrolets first 4x4 vehicles. To provide ventilation, a breather was incorporated on the valve cover.

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Note the lack of ventilation slots in this second era valve cover.

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This is the same cover as above. Notice the oil fill/ventilation cap.

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Here in a maintenance manual, the fill/ventilation cap can be seen in addition to the early style draft tube lacking the PCV components. Also notice that the early radio suppressed vehicles had this ventilation system.

The third and last ventilation system incorporated a PCV system. Although it is not certain, this system came into being somewhere late 1942 and continued through to the end of production in 1945. The valve cover in this system is the same as the second system but the breather is considerably different. This breather is the big one that looks reminiscent to a miniature oil bath air cleaner. The draft tube was eliminated during this evolution as the gas vapors were plumbed into the intake manifold.

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Note PCV components and large air breather.

I hope you enjoyed this information as it should clarify some confusion on the components seen on these trucks. If by chance you think this information will captivate or impress your wife, fat chance as I already tried it and it didn't work.

Have fun guys!

Paul
1941 G4112 Chevrolet with Hercules dump bed


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retro-roco
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Re: Chevy G506 PCV and valve covers

Post by retro-roco » Thu Aug 10, 2017 4:23 am

Excellent analysis and write up Paul! Really enjoyed the info.
Kirk Gustafson
359th Infantry Regt. 90th Div. WWII HRS

1942 Chevy G506 1-1/2 ton 4x4 Cargo
1943 Ben Hur water trailer

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Re: Chevy G506 PCV and valve covers

Post by rjbeamer » Thu Aug 10, 2017 10:04 am

Its interesting as to who the inventor of the PCV valve ventilation system was. (See attachment)
Delmar G. Roos. He was the Chief Engineer that worked for Willys from 1938 through the mid 50's.
Its interesting to note that even though the filing date on this is October of 1943 Willys and GPW started using PCV valve systems in about February of 1943

http://www.cj3a.info/tech/pcva.jpg

Roger

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Re: Chevy G506 PCV and valve covers

Post by Warren Duchesne » Thu Aug 10, 2017 11:13 am

I have seen a NOS kit that converts the early draft tube engine to PCV style engine . I may still have it somewhere . Warren Duchesne

forestry4evr
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Re: Chevy G506 PCV and valve covers

Post by forestry4evr » Sun Aug 13, 2017 3:27 am

Thanks for the positive input, glad it was enjoyed.

It does appear that the Willys PCV is very similar to the ones used on Chevys...it may even be the same part. Roger, your documentation link to the patent certainly debunks the notion that PCV valves were a much later invention.

Here are some of the parts that were used on latest third crank case ventilation system.

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Actual PCV valve is the small cylindrical component projecting from the vacuum junction block, Notice that this intake manifold also has the ports for the cold weather kit.

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Closer view of vacuum port,.
1941 G4112 Chevrolet with Hercules dump bed

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Re: Chevy G506 PCV and valve covers

Post by johnwaz » Thu Aug 16, 2018 9:24 am

Thanks for the info. This thread answered a lot of questions pertaining to the setup on my truck. So now I'm off to find the missing pieces for it. It looks like I'm after the valve itself on the Intake manifold.

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Re: Chevy G506 PCV and valve covers

Post by forestry4evr » Sat Aug 18, 2018 3:24 am

johnwaz wrote:
Thu Aug 16, 2018 9:24 am
Thanks for the info. This thread answered a lot of questions pertaining to the setup on my truck. So now I'm off to find the missing pieces for it. It looks like I'm after the valve itself on the Intake manifold.
The reproduction PCV used on MB and GPW's will work. An alternate part number is AC Spark Plug Type CV-697C, it is a bit longer than the Jeep PCV but hardly noticeable.
1941 G4112 Chevrolet with Hercules dump bed

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Re: Chevy G506 PCV and valve covers

Post by johnwaz » Tue Aug 21, 2018 12:00 pm

I found the AC CV-697C PCV Valve on Rock Auto. Thanks again for the help.


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