old post but worth a shot..... Im running 4 carbs is it necessary to run 4 pcv hoses or can I get away with 3 carbs plugged and one hooked to a pcv? the edelbrock valve covers have the vents on the side and seem to be filled with oil. brand new engine
My bike has a small plastic quad vacuum manifold to each carb from one PCV for better balancing. Easy enough to try manifolding from a single PCV on your setup to see if it makes a difference. Jack E/NJ
My train of thought says that a PCV valve connected at one carburetor of a multi-carb system , particularly with a four carb manifold, might concentrate the oil vapors to the ports closest to that carb. For that reason I would place the PCV valve centrally on the plenum where all ports will get a more equal distribution of the vapor. Fabbing a manifold to all carbs just sounds like too much work and will look too busy also.
I'm not an expert and I may even be educated beyond my intelligence.... so please eat the meat and throw away the bones with anything I post. I used to mess around with turbocharged cars and turbo forums so out of need we turbo owners had to resolve issues in spades that are being discussed here. Because of the higher combustion pressures involved, blow by was just a natural state of affairs. A typical set up to deal with the vapors was a PCV on one side AND a unobstructed "make up" hose from the opposite end or side of the valve cover(s) to a filtered air source air box. When cruising or decelerating, vacuum is high and vapors are drawn through the PCV system into the intake; the make up hose may draw in also. But when under boost (in your case, WOT) the PCV shuts and crankcase pressure with the nasty vapors exits the make up hose into the air box (We used air filter boxes.) This is considered normal and even factory built turbo vehicles come equipped this way. We often upgraded air filters and may also have added a check valve to prevent loss of boost and/or a catch can added to the PCV side, but the basic concept had to remain the same. We noticed that higher boost and more often being in boost mode produced more oil crud in the bottom of the air box. So your personal driving habit is a factor. I'm not saying that worn rings or valves aren't the problem. What I am saying is the oil crud could be considered a normal condition that you have to deal with and accept. To get "neat'n'clean" you may have to trade off for more plumbing clutter. A catch can tucked down low, out of sight could clean up what you "breath" into the intake or help the environment and launch pad at the track if you vent to atmosphere. You have choices. They'er not the perfect answer you may seek but they are choices. By you having both a PCV and a breather, you have the basics but you don't have it enclosed to control where the vapor ends up.
Before we decide that it is blow by which it may very well be get the motor warmed up and then while it is running lift the breather and see if it is blowing by. It will be puffing a little smoke/vapor if it is. Have you changed rocker covers? If there is no baffle under the breather it will blow oil out. If they are original rocker covers the baffle may have fallen off they have been know to do that.
Baffle is easy to rule out, its there or not. I had some real oil guzzlers back in the day. One burned it out the tail pipe and puked it out the breather. I ran straight Valvoline 60-weight in it, blower oil it was called. I wired a shop rag around the breather to keep it from blowing up under the back of the hood and onto the windshield.
My old 283 is tired. I run 2 breathers, 1 in the fill tube and 1 in a valve cover, and that helps reduce the oil seepage. I keep a black scrunchy underneath each one, and periodically I change them out. 15W40 viscosity oil seems to have helped, I think the PE was using a 5W30 or 10W30.
You could always build a small aluminum puke tank. Run a hose from the front of each valve cover to it and put two push on breathers or two small breather elements on the tank. Put a little quarter turn drain valve on the bottom of the tank. Let it breathe into the tank. After all you did say it's a hotrod right? Or you could rebuild it. Lippy
On early or tired engines with draft tubes, a breather cap with a hose connection to the air cleaner will entrain crankcase fumes/vapors that'd otherwise make it into the passenger compartment or splatter on the windshield. No PCV valves, no scrunchies(whatever they are) or no tampons needed. Jack E/NJ
I had bought this Chevy C30 with a very tired Pontiac 215 6-banger, only one I've ever seen. It looked like a Chevy 230 clone. Pontiac blue, 215 on the valve cover. Anyway, the truck came with what looked like an old bed spread cut up to fit between the hood and cowl... I uttered WTF and tossed it out. First rain storm, I realized what the purpose was.
May just be splash. PCV only works on vacuum which comes with closed/light throttle. When you jump on the gas and don't have the vacuum, the oil goes everywhere. Just a baffle in the valve cover or in the breather could make a difference. If it's blow bye, there is no easy way to stop it.
A wet/dry compression test and leakdown test are the best tools for diagnosing any ring blow-by. Leak down test will also diagnose condition of valves and valve guides.
LOL, scrunchies are traditional! I've actually considered doing that, but I don't really want an ugly fat hose running from the valve cover up to the air cleaner assy. The real fix is to rebuild the engine, and that is in plans now. Well, actually I'm looking to build up a 327 to replace the 283. In the meantime, the scrunchies are cheap and easily replaced.
Also, just to clarify, because there have been some posts mistating how a pcv works, a pcv actually closes with very high vacuum conditions. So at idle, depending on the pcv used and the amount of vacuum generated, the pcv may be partially or fully closed. On deceleration or engine overrun, the pcv is definitely closed. This is why the breather can emit gases when the engine is at an idle, the pcv is working as designed, there is pressure inside the block that needs to vent. During acceleration the vacuum is lower and the pcv opens up, but with low vacuum conditions the pressure in the crankcase can exceed the vacuum level in the intake, and then air flow reverses and the breather emits gasses instead of allowing air in. This is a normal condition for all engines, even those with good piston sealing, though obviously it gets worse with increased blow by. But just because the breather is emitting gasses does not mean the engine is worn out. Oil escaping with the gas can be because of poor placement of the breather or lack of baffling. The idea of putting the breather on top of the oil fill tube is that the long distance up the tube will cause the oil mist to coalesce and drop back into the lifter valley.
Good points. The oil itself may be a clue. If it looks clean and not burned it may indicate oil getting past the baffle.
these are real old valve covers and the breather vent is on the side down real low part of the valve cover so I expected some oil in it but seemed to be a lot. altho I have not seen any oil dripping on my exhaust. the engine vents thru the pipe on the front of the manifold where u fill the oil. the engine only has 5000km on it and Im not missing any oil when I check the level.
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