pcv with non emissions carb?
September 18th, 2011, 06:50 PM
#1
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pcv with non emissions carb?
My '70 S has a new Holley 4150 style carb which doesn't have any provision for a PCV connection. I currently have a pcv valve in the right vc and a cheap chrome breather in the left side. I'm getting a fair amount of "smoke" from the breather since the installation of the Holley.
Basically my question is how is the pcv routed if it cannot be connected to the carb?
I was considering putting a pcv in the other vc and plumbing that to the air cleaner as well. I'm fairly sure I'd then need a open style oil filler cap. Does that sound ok?
Basically my question is how is the pcv routed if it cannot be connected to the carb?
I was considering putting a pcv in the other vc and plumbing that to the air cleaner as well. I'm fairly sure I'd then need a open style oil filler cap. Does that sound ok?
Last edited by DJS70cutlass; September 18th, 2011 at 06:53 PM.
September 18th, 2011, 07:22 PM
#2
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Location: The Hudson Valley
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The PCV in the right valve cover is connected to the intake manifold, right?
The PCV regulates the amount of scavenging of crankcase gasses by the intake manifold (don't want to have a giant exhaust leak at idle), while the other end is just the entry point for air into the crankcase to replace the air sucked out and into the manifold.
Therefore, it really doesn't matter what you have on that side, so long as it's open and it keeps big bugs from being sucked in. The factory arrangement was to connect it to the air cleaner (on the outside of the element, not exposed to manifold vacuum), pretty much so you wouldn't see that smoke, as far as I know, which is to say that it is NOT connected to the carb at all (the vacuum connection to the PCV is usually on the very bottom of the valve plate, but is in a location that's basically the same as being connected directly to the manifold).
So, to answer your question, the PCV is connected to manifold vacuum, probably at the very bottom of the carb, and the breather is left open to the air, usually with a coarse filter over it, but can be routed into the outside area of the air cleaner if you prefer (a chassis punch, familiar to old-time radio hobbyists, is the neatest way to make the roughly 7/8" hole you need in the side of your air cleaner).
- Eric
The PCV regulates the amount of scavenging of crankcase gasses by the intake manifold (don't want to have a giant exhaust leak at idle), while the other end is just the entry point for air into the crankcase to replace the air sucked out and into the manifold.
Therefore, it really doesn't matter what you have on that side, so long as it's open and it keeps big bugs from being sucked in. The factory arrangement was to connect it to the air cleaner (on the outside of the element, not exposed to manifold vacuum), pretty much so you wouldn't see that smoke, as far as I know, which is to say that it is NOT connected to the carb at all (the vacuum connection to the PCV is usually on the very bottom of the valve plate, but is in a location that's basically the same as being connected directly to the manifold).
So, to answer your question, the PCV is connected to manifold vacuum, probably at the very bottom of the carb, and the breather is left open to the air, usually with a coarse filter over it, but can be routed into the outside area of the air cleaner if you prefer (a chassis punch, familiar to old-time radio hobbyists, is the neatest way to make the roughly 7/8" hole you need in the side of your air cleaner).
- Eric
September 18th, 2011, 07:24 PM
#3
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The PCV needs to bee hooked up to manifold vacuum. The smoke you are referring to is blowby. Most carborators have a large manifold vacuum port on them. If not, there may be one directly on the manifold.
September 19th, 2011, 03:09 PM
#4
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Thats where my problem is, the carb has no such connection, the only one thats there is labeled power brake. I figured the pcv could'nt go to it because it would act like a huge vaccum leak. This port is capped because the power brake is piped to the intake directly.
September 20th, 2011, 07:04 AM
#5
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No, right now its going to the air cleaner and I realize thats not right. I've just got to figure out how to do it right this time
Thats where my problem is, the carb has no such connection, the only one thats there is labeled power brake. I figured the pcv could'nt go to it because it would act like a huge vaccum leak. This port is capped because the power brake is piped to the intake directly.
Thats where my problem is, the carb has no such connection, the only one thats there is labeled power brake. I figured the pcv could'nt go to it because it would act like a huge vaccum leak. This port is capped because the power brake is piped to the intake directly.
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