04-24-2022, 01:21 AM | #1 |
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1964 292 Valve Cover
I have a 292 cast in 1964 that is in my 1968 C20. Its a bit of a mystery how and why it is there, anyone curious can check out the latest posts in my build thread in my signature, I'd love to hear your opinion.
Anyway, I have always been confused by the nature or need for PVC valves and breathers and the like - for the simple reason that I do not understand why some engines have them and some do not. Why not all or none? This has come up because I bought what I thought was a really cool valve cover for my 292 that has the "Chevrolet" script on it. Belatedly, I noticed that it has a hole in the driver's side for what appears to be a PCV valve or tube going to the carb. The original valve cover that is still on the engine does not have this provision. Can I add the PCV valve to this engine so I can use this valve cover? Would it benefit the engine, or should I trust the engineers at GM in 1964 that the engine does not need it? If I use this valve cover without the PCV/tube, is there a recommended way to plug that hole? First pic is of my engine right now, second is what I am referring to.
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DAVE Edmonton, Alberta 1959 Apache 1967 K20 1968 C20 1970 C10 1972 GMC 2500 1981 C10 |
04-24-2022, 06:03 AM | #2 |
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Re: 1964 292 Valve Cover
That is the fresh air intake for the PCV system. There should be a hole in the top of the valve cover toward the back for the PCV valve.
I just got finished installing a 292 in my 67 C20 and I used the script valve cover on mine.
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67 C10 283 T5 swapped longbed fleetside = wife's daily driver 67 C20 292 (originally a 250)4speed longbed fleetside w/original wooden bed=my project truck 67 C10 283+.060 (so a 292 as well)T5 swapped longbed fleetside=my DD 72 C1500 Sierra Grande 350 TH350 longbed fleetside=wife's fair weather truck Can you tell we are fans of longbed fleetsides & 67s Chris |
04-25-2022, 07:42 AM | #3 |
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Re: 1964 292 Valve Cover
Early covers have only the oil fill hole in the front and run a breather in it ('67 Biscayne).
Next step was early emissions, PCV in rear top, air in on side at front with a hose to the air cleaner, and flat oil fill cap ('66 BelAire California emissions, 1969 C10). Then you start getting into the no script covers. I 'think' the GMC's may not have had script covers, never owned one that early. I think Chevy went to no script covers with the integral heads, 1976? or so.
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04-25-2022, 12:14 PM | #4 | |
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Re: 1964 292 Valve Cover
Quote:
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67 C10 283 T5 swapped longbed fleetside = wife's daily driver 67 C20 292 (originally a 250)4speed longbed fleetside w/original wooden bed=my project truck 67 C10 283+.060 (so a 292 as well)T5 swapped longbed fleetside=my DD 72 C1500 Sierra Grande 350 TH350 longbed fleetside=wife's fair weather truck Can you tell we are fans of longbed fleetsides & 67s Chris Last edited by 67 twins; 04-25-2022 at 12:19 PM. |
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04-25-2022, 01:43 PM | #5 |
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Re: 1964 292 Valve Cover
Around 1964 automobile manufacturers started adding a PCV valve to their engines. This was primarily motivated to reduce pollution caused by venting the crankcase vapors directly into the atmosphere. The source of these vapors is combustion gasses leaking past the piston rings. Earlier engines simply had a breather from the crankcase as you mentioned in your post.
The PCV valve is more complicated than most people realize. One end is connected to your crankcase, usually via a hole in the valve cover. The other end is connected to your intake manifold downstream of the carb. With the engine off, the PCV valve is closed. After starting, with the engine idling, the intake manifold vacuum is high. The PCV valve is "pulled" open by this vacuum a small amount to allow the crankcase vapors to be sucked into the intake manifold and reburned in the engine. As the throttle is opened and a load is placed on the engine, the vacuum drops. Since this happens at higher engine speeds, there is more blow by in the crankcase. At this lower vacuum level, the PCV will open more and allow the added gasses to be passed back into the engine. The PCV operates in three states, closed, lightly open, and fully open. Even though this was originally conceived to control emissions, they found that by removing crankcase vapors with the PCV, the engine stayed cleaner and longevity increased. The other benefit was with reduced crankcase pressure, oil leaks went down because the gaskets did not have to hold back as much pressure. Here's a great video on PCV operation: https://www.youtube.com/watch?v=pr5MZni4_Bc I'm not a big fan of off-the-shelf PCV valves. They may not do much good if they aren't for your specific engine combination. Here's a product that allows you to "tune" the PCV valve for your engine. http://mewagner.com/?p=444 |
04-25-2022, 02:09 PM | #6 |
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Re: 1964 292 Valve Cover
Cris thank for that info, I have some research to do. It sounds as though with a few more parts... I could add a PCV that would work for this engine?
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04-25-2022, 03:04 PM | #7 |
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Re: 1964 292 Valve Cover
dagnabbit:
You could add a PCV to your engine. I have a 292 in my 1963 C10 and run a PCV, and obviously later year 292's ran a PCV. There are a couple of things to watch out for in setting it up. The PCV valve must be protected (baffled) from sucking up any splashing oil in your valve cover. A valve cover designed for a PCV usually has some kind of piece of sheet metal shielding where the PCV sits on the cover. The more baffling the better! You also need a source of fresh air for the system. This is usually a simple breather mounted on the valve cover as well. Typically, the PCV mounts in the back of the cover and the breather up front. Some systems pull fresh air from the air cleaner assembly. And baffle the fresh air breather as well! If your 292 is stock, you could use a reputable supplier for a stock PCV valve from a later year, say 1966. Otherwise I would recommend the ME Wagner product. |
04-26-2022, 10:00 AM | #8 | |
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Re: 1964 292 Valve Cover
Quote:
Would this system work? Hope I'm not hijacking too bad here. |
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04-27-2022, 03:30 PM | #9 | |
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Re: 1964 292 Valve Cover
Quote:
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04-27-2022, 03:47 PM | #10 |
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Re: 1964 292 Valve Cover
I’ve seen a chrome push in breather in that valve cover hole.
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04-27-2022, 03:51 PM | #11 |
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Re: 1964 292 Valve Cover
Why not acquire another valve cover without the hole?
Red deer swap on Friday and Saturday. https://vintageautoclub.ca/events/71-cavac-swap-meet You might even find a dealer there for the Wagner pcv. |
04-28-2022, 10:37 AM | #12 | |
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Re: 1964 292 Valve Cover
Quote:
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04-28-2022, 01:31 PM | #13 |
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Re: 1964 292 Valve Cover
jumpsoffrock:
The road draft tube is a good place for a breather or for the pcv valve itself. I believe they make kits to turn the road draft hole into a spot for a pcv valve. Check places like Classic Parts. I am not sure of the baffling on the road draft tube port, but some kind of baffling must be in place. If you use the road draft tube for the pcv, you would use a breather/filler cap on the valve cover for fresh air. Cris |
05-25-2022, 03:47 PM | #14 |
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Re: 1964 292 Valve Cover
So, to recap, the existing (orange) valve cover does have a PCV valve going to vacuum, etc on the top rear of the cover.
But the valve cover I wish to use (cause it has cool Chevrolet script on it) has not just that, but also provision on the front driver's side for a (cold air?) tube going to above the carb, below the oil bath air cleaner. This week I remembered that I did have one of these tubes, it was on a 67 250 that I scrapped a few years ago and I kept it in case it proved to be of any use. If I wish to use it I will need the rubber grommet for the side of the valve cover I want to use. So my questions are:
Thanks for all the help.
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05-25-2022, 04:19 PM | #15 |
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Re: 1964 292 Valve Cover
Search for baffle/grommet.
Many sizes available. Like this from summit. https://www.summitracing.com/parts/m...CABEgL7svD_BwE |
05-27-2022, 08:06 PM | #16 |
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Re: 1964 292 Valve Cover
Im a V8 guy but I get the impression your new cover should have a non vented oil fill cap like the 2nd pic in your first post since the tube gizmo seems to be the air inlet. I wonder if now that you have a vented cap and a pcv, if you couldn't just plug the hole on the side and forget about the tube thing.
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05-28-2022, 10:16 AM | #17 |
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Re: 1964 292 Valve Cover
I'm new to sixes too - not that I am much of an expert in V8s either - so I will have to read that tutorial on PCV systems again, and check if either of my oil caps are vented or not.
If I cannot find the right grommet I might have to evaluate how important the Chevrolet script on the valve cover is to me, since I want to paint the engine and bay. Incidentally, I could have started a whole thread on the difficulty of acquiring Alpine Green Engine Enamel in Canada: it is unobtainable, and since spray paint is considered a hazardous material by some shippers, ordering from the US is a royal pain as well. Finally got two rattle cans worth arriving next week.
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05-28-2022, 11:15 AM | #18 |
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Re: 1964 292 Valve Cover
I knew a guy who cut the Chevrolet writing off his valve cover and welded it onto the cover he wanted to use.
That was on a sbc but same idea. |
05-28-2022, 01:38 PM | #19 |
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Re: 1964 292 Valve Cover
My local auto parts store had many grommets in the "heip" section.
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05-29-2022, 12:07 PM | #20 |
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Re: 1964 292 Valve Cover
I am so used to buying stuff online at this point that it never occurred to me that I could just bring the valve cover down to the store and try grommets until one fits. I will do that when I get a chance! But, if some grommet guru knows a part number that would be appreciated. When I find the one I need I will post it myself.
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05-29-2022, 02:58 PM | #21 |
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Re: 1964 292 Valve Cover
My '68 C/10 Stepside rolled out of Fremont sometime in early 1968 with a factory L-25 292 L6. Being a California truck with an in-state end user, Felix Chevrolet, it had smog equipment which included a PCV system.
While I ditched the A.I.R. compresser and fittings to the head a year after I bought it, while stationed in North Carolina, I kept the PCV set up. When I upgraded to an Offenhauser intake, 4 barrel Holley carb*, and Clifford headers, after getting out of the service, I reconfigured the PCV system to the new equipment. Now the hot gasses exit the top of the rear valve cover thru the PCV Valve into a 3/8'' hose that plugs in front of the carb. A 1'' [~] hose goes into the side grommet on the forward valve cover and connects to an elbow fitting that gets fresh air thru a hole in the bottom of a Moroso air cleaner. Works fine. * Holley 390 wore out after 250,000 miles. I replaced it with a 500 CFM Edelbrock 1404 when the original 292 was rebuilt after the first rebuild ran 25 years.
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Every 25 years I like to rebuild that 292, whether it needs it or not. Last edited by '68OrangeSunshine; 05-29-2022 at 04:42 PM. |
05-29-2022, 03:02 PM | #22 | |
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Re: 1964 292 Valve Cover
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Every 25 years I like to rebuild that 292, whether it needs it or not. |
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05-29-2022, 03:37 PM | #23 |
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Re: 1964 292 Valve Cover
I can only get one pic up at a time, so please excuse the gratuitous post count bumps.
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Every 25 years I like to rebuild that 292, whether it needs it or not. |
05-29-2022, 04:11 PM | #24 |
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Re: 1964 292 Valve Cover
That filter in the base is a good idea.
Works as a filter for the air and as a spark arrestor. If someone is looking for one, I’ve found plastic 90 degree elbows in the plumbing section at H.D. Or other hardware stores. |
05-29-2022, 04:31 PM | #25 |
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Re: 1964 292 Valve Cover
The 90* elbow I'm using is actually a Ford PCV device, that's all plastic. It had an inside flap [at 45*] that passed gas when pressure was applied from one end. Like a Kazoo. I bored it out to just be an elbow. Found in the HELP section at the Auto Parts store.
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Every 25 years I like to rebuild that 292, whether it needs it or not. |
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