The Stovebolt Site Forums The Shop Area Engine Shop Will this crankcase vent harm my ’54?

Hi Bolters,

I’ve been reading recent postings re: crankcase ventilation. Will this crankcase vent harm my ’54?

A PVC valve was added to my ’54 3100 at some point in its life. The truck runs well, doesn’t use oil, and doesn’t smoke. Will this setup damage my engine? Should I remove the PVC valve, install a road draft tube, and replace the valve cover?

My number one goal is to protect the engine. If changes are needed, I would like to return to factory appearance.

The valve cover is vented to a PVC valve in the intake manifold.
Pic #1
Pic #2

The PVC valve (AC Sparkplug Type OV-693G) is screwed into the intake manifold. The truck has electric wipers.

A rubber hose runs between the PVC valve and a pipe that is bolted into the valve cover.

A bent rubber pipe is press-fit into a hole on the top of the valve cover.
Looks like there was a mounting plate for the rubber pipe at one time. The four slots on the valve cover are open.

There is no road draft tube. A freeze plug covers the opening.

I believe that the truck was restored in California. Possibly altered to meet emissions requirements?

Engine serial number: 0369873F54U
Block Date Casting Code: CON4 B264
Vin # H54O007554

Thanks in advance for any insight that you can give me.

- Lonnie

Unless you want an original appearance, if it ain't broke, don't fix it.

Your PCV plumbing is different from original; however, that does not mean that your set-up is bad/wrong. Maybe someone will study your plumbing and comment on it (thanks or posting such nice photos).

The pictures are great, the only thing that doesn't look right is using a slotted valve cover, and no breather cap.
Basically your sucking crankcase fumes and whatever air and dirt thats coming in the vent slots in the cover.
The rubber elbow may have run to the air cleaner for an intake air supply,is there a hole in the air cleaner to match ? But again with the slotted cover it doesn't make sense.
Normally you would use a solid valve cover, and a breather type cap, otherwise the setup looks fine.
Hopefully there is some kind of baffle inside the valve cover to stop oil being sprayed directly into the vacuum hose where its connected.
If you want it to look original however, then you want the road draft tube back on it, but be aware they can get dirt into your engine, and they drip on the ground in your garage, and everywhere else, you sure you want that?

I guess the other question here, is does a slotted valve cover belong on a '54 ?
I'm not sure about that having little experience with that year, Butsomebody here will know for sure.

A properly set up PCV system actually makes the engine last longer because less dirt gets drawn into the engine by the ventilation system. Normally, the road draft tube is cut off (leave the canister that plugs into the block in place) and the PCV valve is adapted into the hole where the draft tube used to be. A solid valve cover (no slots) is installed, and an oil filler cap with a hose nipple is installed with a tube running to the clean side of the air filter. Air is drawn into the valve cover, goes to the crankcase, and is sucked out of the road draft canister, through the PCV valve, and into the intake manifold, taking crankcase vapors with it.

The way yours is set up, there will be little or no purging of the crankcase, other than whatever vapors find their way up through the pushrod valley and into the valve cover. Since your valve cover is vented, even less flow from the crankcase will happen. Keep the PCV system, but improve its design somewhat.
Jerry

1954 was the last year to use a vented valve cover, and the only four bolt mounting with vents.

It looks to me that the vents in your 54/55 valve cover have been "after-market" welded closed - which would be correct in a PCV set-up?

I have seen a number of 54 covers with the vents welded. I wonder if the factory welded these when the PCV system was used, like on the big truck 235 and 261. The Parts book 0.386 only lists one cover for 54.

If it were me, I would close up the extra holes in the valve cover and insert a filtered vent where the old draft tube hole that is plugged. The other possibility is to put a PCV valve where the draft tube was and put one filtered filler cap on the valve cover, closing up the other holes.

On my truck I blocked the side tube inside the draft tube and installed the PCV valve on the top of that tube. I installed a filtered vented oil cap and I will be closing up the slots on the valve cover.

On my 1954 the road draft tube was replaced with a closed top version with a PCV valve fixed on the side of it. This was fron the factory.

Another illustration of the 1954 PVC-equipped engine's tube that replaced the standard road-draft tube.

That is pieces of the AC (AC spark plug of General Motors Corporation) “California State Approved” crankcase ventilation system. California required most 1950 and later cars and trucks to be retrofitted with a PVC system when a used vehicle was sold. The program originally started from January 1, 1964 and ran through January 1, 1966.

The installation required two kits, CV3 and KV1002. CV3 consisted of an intake manifold fitting, 3/8 hose, CV609 PCV valve, hose clamps and fitting to the valve cover for an open PVC system. KV1002 closed the system, it consisted of 5/8 inch hose fittings, 5/8 hose to connect air cleaner to the valve cover for clean air induction, sealed oil fill cap and a plug to close up the hole after the road draft tube was removed. The slots on the valve cover were soldered closed.

I believe your PCV valve is a CV693C. If so, it is installed backwards so the flow is backwards. CV693C is designed to mount on the ventilator for the factory installed PVC system on 261 engines as well as California 1960-62 235 engines.

If you want to keep this setup, I would recommend finding a CV609 valve. I would reconnect the open hole on your valve cover with a 5/8 hose to your air cleaner. The CV609 valve is spliced into the hose that connects the valve cover to the manifold fitting. You will need to find some hose fittings, hoses and a CV609 PCV valve.

Uncovering the history and the probable actions of former owners is part of the joy in owning an old vehicle. I have the same joy in tracking the history of our 1908 bungelow.

>> CrankyOldDude, your "California State Approved" crankcase ventilation info may be the missing link. As I stated, I believe that the truck came from California. The pipe on the side of the valve cover appears to be purpose-built, so it could have come from the kit. The hole on the top of the valve cover has two small holes on each side that probably held screws and a mounting plate for the hose to the air cleaner. I betcha that the owner drilled an aftermarket aircleaner to accept the hose rather than drill the oil bath cleaner.

Looks like he removed the hose for the air cleaner when he reinstalled the oil bath cleaner and substituted the bent rubber stub on the back of the valve cover. It brings dirty air into the engine.

Sounds like the CA system pulled clean air from the air cleaner across the rocker arms (back to front) then into the intake manifold through a PVC valve. There was no vent to the crankcase as in Tim's original equipment diagram.

>> Tim, chevman32, truckernix, Pre '68 Dave, Jerry, and Andy46 - thanks for your insight and suggestions. To answer some questions:
1) I thought that the slotted vents were open since I can poke a fine wire through the front one. But on closer inspection, it looks like they were plugged up with something ... not welded or soldered.
2) There is no baffle behind the pipe on the side of the valve cover.
3) There is no hole or plugged up hole on the oil bath air cleaner.

>>> And now some comments and more questions:
+ I don't want to drill a hole in my oil bath air cleaner.

+ I agree that dirty air is entering the engine through the bent rubber pipe on the top of the valve cover and a little through the open sections of the slotted vents. The truck isn't driven much. Would it help to replace the bent rubber pipe with some type of filter? Would it be better to plug the hole for the bent rubber pipe and replace the oil filler cap with a filtered cap?

+ CrankyOldDude - Regarding the PVC valve being installed backwards, are you saying that the airflow through the valve should be from the threaded end to the barbed end, instead of the current barbed to threaded?

+ I agree that the crankcase is not being vented. Will the engine be damaged if I leave the plug in the hole for the road draft tube?

+ Since the truck runs ok and I don't drive it much, should I just follow Tim's original suggestion "if it ain't broke, don't fix it" and move on to other projects that need attention?"

As I've said before ... This is a great forum. Your depth of knowledge and desire to help is unsurpassed.

Thanks,

- Lonnie

+ CrankyOldDude - Regarding the PVC valve being installed backwards, are you saying that the airflow through the valve should be from the threaded end to the barbed end, instead of the current barbed to threaded?

Yes, it is backwards. That PCV valve will close up with some manifold vacuum unless it is gummed up or broken. It is the wrong valve for the system.

I would install a road draft tube with a vented oil cap or repair the PCV system. I seen a number of these old 235s with the PCV system partially removed and the engine left un-vented. The engines were all caked up, with stuck pistons rings, clogged oil passages and oil blowing out almost every seal. Tampering with these systems in the early days was common, people thought they would cause engine performance problems. The "State Approved" retro fit kit did look out of place.

The factory PCV systems as seen on 261 engines do show up on E-Bay a few times a year. These were also factory installed on California 1961 and 62 235 engines as well. They do look much better and look like they belong on the engine.

CrankyOldDude -

Thanks for the update. For now, I'll try to return it to the original road draft tube venting. I have a source for a road draft tube. Just need a new un-altered '54 valve cover to make it look right. Sounds like I'll also need a bucket to catch the oil from the R.D. Tube before it hits my garage floor!

I'll keep my eye open for a factory PCV system. I'd rather intall the factory system than to do another home-made PCV system that may be as bad as the one that I have.

The truck runs well. Thanks to you and to all for showing me how to keep it running well.

- Lonnie