Thanks 62. I'll give it a shot. Just need to run down some v/c vents for these cal customs. Also, I was talking about this subject with a buddy today and he said some guys don't hook up the vac advance on the distributer. Have you heard of this?
I can't imagine a vac advance distributor with the vacuum disconnected..? The whole idea is to advance the timing as RPMs increase... maybe someone else has the stinky on this one. Anyone have any more input on these PCV setups? Seems to be a lot of interest - let's hear it.
Hey! I've got a stupid question. Reading some of the posts about PCV valves and old valve covers makes me wonder if keeping the old look of Cal-Custom etc valve covers is worth all the hassle. I mean, I appreciate how the old parts look, but it can't be argued that modern valve covers/PCV systems work better. It sounds more like people are into restoration at times than hot-rodding. If you have an old manifold with a front filler tube and you want to run a down draft tube or whatever to keep solid valve covers more power to ya. But, talking about drilling holes and all sorts of jerry rigging seems kind of crazy to me.
I agree with 62. I disconnected my vent tube in the rear valley cover and put a PCV in it's place, running to the rear base of the carb. It now sucks fumes out of the crankcase and fresh air is pulled in through the breather.
I have an Offy 3X2 setup on my roadster and it was puking all over my windshield too..I put a 3/8 hole in the back of the intake where the 3rd carb is,in front of the dist.Then tapped it and put a 3/8 90degree brass fitting in it.I then took my breather/filler tube and drilled a 3/8 hole in the side of it at the bottom.I then took a piece of 3/8 tube about 1 qnd 1/2' long and welded it on the filler tube.I put a piece of rubber gas line on it and put a pcv on it and then joined it to the brass fitting with another piece of gasline.Works like a hot damn.I might be able to take some pics later........Shiny
I saved most of the post from the last time this came up... but here is a nice figure that I believe DrJ posted of a pcv in the filler tube.
What DrJ is referring to is a "closed" PVC system. Prior to that you had "open" PVC systems where the air was drawn in through the breather in the oil filler cap, circulated through the crankcase and was then pulled through the PCV valve into the intake manifold or carb. If everything else is OK, the open system will work just fine. You should be able to use any manifold vacuum port to attach the PVC hose or valve. In the intake manifold or carb base, shouldn't matter. One other consideration is that ideally you want the air to circulate through-out the crankcase, so the further you have the crackcase PVC port away from the breather the better. The filler tube set up will work just fine however. For the PVC on my Cad motor I cut the road draft tube off and welded on a hose fitting adapter. Then ran the hose from that point through the PVC valve to a manifold vacuum port on the base of the front WCFB. Works well so far, no oil blown around and no more oily film on the underside of the roadster. warbird
[ QUOTE ] What DrJ is referring to is a "closed" PVC system. Prior to that you had "open" PVC systems where the air was drawn in through the breather in the oil filler cap, circulated through the crankcase and was then pulled through the PCV valve into the intake manifold or carb. If everything else is OK, the open system will work just fine.... warbird [/ QUOTE ] Yes the open system will work but when the blowby overcomes the capacity of the PCV valve it will blow back out the breather and oil mist the windshield on a hoodless car. I've seen more than one of these open systems with an ugly oil soaked gym sock stuck over the breather to try and collect the oil coming out of them. You choose...
[ QUOTE ] Yes the open system will work but when the blowby overcomes the capacity of the PCV valve it will blow back out the breather and oil mist the windshield on a hoodless car. I've seen more than one of these open systems with an ugly oil soaked gym sock stuck over the breather to try and collect the oil coming out of them. You choose... [/ QUOTE ] IMHO, if you've got so much blow-by that it overwhelms the PCV system, you've got a problem inside the motor that you ought to fix. Knew some one that bought an early '60s Chev a few years ago. It had belonged to an old couple that hadn't driven it much and it probably had stuck rings. He finally got tired of the mess around the road draft tube and ran a hose from the end of the tube back to rear bumper. Solved the problem, but don't know if drivers following him cared much for the oil on their windshield. warbird
I'm a little leery of the vented oil fill caps. In particular the ones that take air directly from the atmosphere. The later Y-block Fords as well as the late 60's 390's had a vented oil fill cap that had what looked to be a horse-hair filter within. It did not stop the dust etc. from entering the engine and in fact, once the cap was off you could feel grit in the oil filler tube. With that in mind I made a closed cap for my 462" Buick engine and tapped incoming air from inside the air filter. Not on the inside of the sheet metal housing and outside the filter. Clean air, same as the carb gets with the vent line tapped to the inside of the filtered area. The PCV valve is directly behind the carburetor above the lifter valley. What helps with the Buicks is their intake 'bathtub' gasket that keeps oil splash off the underside of the intake manifold and away from the PCV valve. In fact, my dual quad setup has provisions for a PCV valve directly behind the rear carb and I do run one. I have run the filtered fresh air line from air cleaner directly to a 1/2" thick fuel pump blockoff plate that had an AN fitting for #8 line. That worked well as did running two lines, one from the blockoff plate and one from the sealed filler cap, both to the filtered air supply area. That done to gain some crankcase air inlet capacity, but it wasn't really needed. Here's a pic of the filler cap in question. It's drilled and tapped for a #8 AN to 3/8" NPT as you can see and also center drilled from the bottom to meet the side drilled hole. This particular cap, even though aluminum is a touch heavy and the next one will be hollowed out with a thin piece epoxied or bolted on top.
[ QUOTE ] Yes the open system will work but when the blowby overcomes the capacity of the PCV valve it will blow back out the breather and oil mist the windshield on a hoodless car. [/ QUOTE ] Hoodless being the operative word here. Air going by an open element or even a covered breather cap will act just like the road draft tubes of old and "pull" oil mist out of the crankase and onto the engine compartment & windshield. Run a hood, run a closed system, or design a baffle (probably ugly, but not quite as bad as an oil soaked sock!) around your breather to keep the oil where it belongs...
i wanna thank you guys. i finally understand the PCV concept now. i printed off the previous 2 PCV valve posts and didn't understand what was going on until now, for some reason. not sure what system i will use, but i am really greatful for everybody that explained this and that about this whole thing, now i pretty much know what i'll have to do to run my old tymee chevy script covers on a PCV equipped '68 327. cool.
[ QUOTE ] Hoodless being the operative word here. Air going by an open element or even a covered breather cap will act just like the road draft tubes of old and "pull" oil mist out of the crankase and onto the engine compartment & windshield. Run a hood, run a closed system, or design a baffle (probably ugly, but not quite as bad as an oil soaked sock!) around your breather to keep the oil where it belongs... [/ QUOTE ] Sorry guys, but I'm running an open PVC system on a Cad motor in a hoodless '31 roadster. No oil!! Works for me. Nuff said. warbird
I know im digging up a old post but its a good one, ive got a question when you replace the draft tube setup with the pvc set up do you remove the internal filter set up or deflectors. my olds 324 has a big can do i remove that when i convert it to pcv. cory
I'm at the same place on a 303+. You need to keep the can inside the lifter gallery since it's a baffle and otherwise you'll suck oil through the PCV. There's a lot of oil flying around in there in a running engine. I think Yorgatron has some experience putting a pcv on a 324. Just reread your post. Want to be clear that the big can filter near the end of the road draft tube goes along with the rest of the tube.
I drilled and tapped my intake just in front of the Dist., used a 90 degree adapter and a screw in PVC valve. Took the setup to the local NAPA store and got a custom hose and all the fittings. Make sure that you make and install a baffle under the manifold to keep oil out. This is better than coming off the filler tube as you are drawing across the complete valley area.
In my '31 Plymouth with a big block Chevy, I installed an inline PCV valve in between one valve cover and manifold vacuum under the carb and there's a screened breather on the other valve cover. It works fine driving around slow, but if I really get on it, there's too much blowby I guess, and the pressure builds up and a little oil sprays out of the breather and also out through the front timing cover seal around the crankshaft snout. It's a 454 bored out to 468, and really pumped up with a hot cam and high compression pop-up pistons and it's probably got at least 500 horsepower. I have heard several guys with hopped up big block Chevys having this same problem with oil leaking like that through the timing cover seal only when they stomp on the gas too much. One guy I know with a big block Chevy installed four breathers and that solved the problem of oil blasting out of the timing chain cover at least, so I'm thinking of doing that someday, but I kind of hate to have to cut up my old Cal Custom valve covers to install more breathers. If you watch slow motion older movies of drag racers, you can see clouds of oil mist and smoke spraying out of the multiple breathers when they floor it. Modern drag racers usually have fat hoses running from the valve cover breathers to venturi tubes in the headers to suck the fumes out and burn them in the headers -- or they run the hoses to "puke tanks" to catch all the oil mist and blowby crap that comes flying out of the crankcase. So a PCV valve works okay on a tame engine not working too hard, but at full throttle, you might need some way to vent the built up pressure in the crankcase that goes beyond what the PCV valve can handle. Also, at full throttle, you don't have any vacuum, so the PCV valve isn't working anyway. The crankcase fumes have to vent somewhere -- so they're going to come spraying out of the breathers if you have open breathers. After thinking about this, I think I'm going to run more breathers and just wrap a sock around them for long trips. It's kind of Mickey Mouse, but it beats wiping down all the oil mist that sprays out everywhere when I punch it.
I'm with you; mine only pukes at over 65 mph. Not a tight engine though. Instead of a sock, I use a tennis wrist sweat band on the breather cap. Gets funky, can it and get another one. Cheap too.
I read a article in streetrodder magazine a couple of years ago , and did just what they said , drilled & tapped intake , used a threaded pcv , made a flat aluminum sheild under intake , it sucked so much oil it fowled plugs ! so I took a stock chevy valve cover baffle out & mounted it under intake , with a aluminum sheild on the bottom , to block oil ( there is a hell of a HURRICANE going on under intake ) it works very well , but it took alot of immagination . I wish I would have taken pictures . good luck
He is right and if i remember correctly the early like 65 66 gto had the pcv in the intake . i always thought it was a good idea and makes everything look clean Dave
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