Blow by smoke through the PCV system

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Bard Beach
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Blow by smoke through the PCV system

Post by Bard Beach »

My 63 Monza Powerglide had a road draft tube when I bought it, but have recently switched it to a PCV setup.
I know from having that road draft tube that the blow by smoke increases quite a bit after driving around 30 minutes or more.
Since the PCV installation I've noticed a bit of coughing and unsteady acceleration after a bit of driving/ when the engine warms up quite a bit. It seems to be wanting to stall if in drive at stoplights. Also seems to work better with slow steady acceleration, and coughs if I step on the gas.
Can blow by smoke choke out the carburetors? Or maybe it's from re-installing the carburetors incorrectly after PCV installation?
Trying to troubleshoot it.. running sea foam through the fuel tank in an attempt to clear the carburetor a bit in case it might be related to that.

Any suggestions or related experiences appreciated!
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Re: Blow by smoke through the PCV system

Post by 64powerglide »

Are you getting any white exhaust smoke?
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Re: Blow by smoke through the PCV system

Post by Trip »

Did your PCV valve come from a Corvair supplier?

I know my FLAPS gave me the wrong one and I believe it caused the same kind of problems you describe. I personally prefer a road draft tube to avoid any possible issues. Alternatively I have used the later model Corvair PCV that has an orifice instead of a PCV valve.

The biggest common mistake with Corvairs is venting the PCV to the engine room, Jay Leno's Yenko Stinger is set up this way, as was my Corsa at one time. The problem is that the heater system then pumps the blowby into the passenger compartment. Maybe Jay Leno's Stinger doesn't have a heater setup installed at all.
Ray "Trip" Rodriguez III
Gouldsboro, PA
66 Corsa 140 coupe
65 Corsa 180 Turbocharged coupe
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bbodie52
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Re: Blow by smoke through the PCV system

Post by bbodie52 »

The Positive Crankcase Ventilation (PCV) system was designed by engineers to deal with crankcase ventilation requirements in a wide range of engine operating conditions — full throttle, closed throttle, partial throttle, high RPM, low RPM, and everything in-between. The baffle plate and vents, the PCV tube, the PCV valve or fixed vacuum orifice that is connected to the engine intake, and the PCV breather connected to the air cleaner, are all part of a dynamic system design that is intended to function continuously during all engine operating conditions.

1962 and earlier Corvair engines did not have a PCV system. Like most earlier engines, they were fitted instead with a simple road draft tube.
Image
Image
Image

When road draft tubes were used, they were simple unfiltered tubes that routed from the Corvair crankcase cover directly downward, where they vented through a hole in the sheet metal cover under the right side of the engine, adjacent to the oil pan. There was never a tee on it that connected via an orifice to manifold vacuum at that time. The first stage of Positive Crankcase Ventilation that appeared around 1963 utilized an appropriately-sized vent restriction (PCV valve design AC-CV584) that limited the amount of crankcase fumes and air that could be drawn into the vacuum balance tube that connected at the base of the carburetors to the intake manifold. This was essentially a "vacuum leak" that was engineered into the system to draw some of the crankcase fumes into the intake manifolds to be burned as they passed through the combustion chambers and ultimately out through the engine exhaust system.

Part of the main vent tube is ALSO CONNECTED TO THE AIR CLEANER. This allows those excess crankcase pressures that cannot be completely drawn through the PCV valve and into the intake manifold to be managed by instead having them drawn through the air cleaner assembly and into the carburetor intake throats. The secondary vent path into the air cleaner assembly allows for excess crankcase pressures that routinely occur at higher engine speeds and that would also routinely overwhelm the limitations of the PCV valve vent path. (This necessary connection also allows air that is filtered by the air cleaner air filter to access the engine crankcase, providing a balancing effect for the crankcase so that crankcase vacuum and pressure can be maintained at approximately normal atmospheric pressure). Without the connection to the air cleaner assembly, the sealed crankcase has no way to "breathe", because half of the normal PCV system design would have been omitted.

The fixed orifice only became a part of the PCV system in 1964-1969. The use of a fixed orifice was not a part of the 1964 system in Forward Control (FC) vehicles and in air conditioned cars, because of clearance limitations in the van and truck engine compartments and in cars equipped with air conditioning. Those vehicles retained the earlier design of the air cleaner assembly with its associated PCV valve design (AC-CV584).

All PCV systems have connection between the main vent tube and the air cleaner, which is necessary for proper crankcase ventilation. With the use of custom individual air cleaners, you can replicate the portion of the PCV system that is missing by installing a connection to the right air cleaner. The custom air cleaner can be modified to provide a hose connection at its base.
1963 PCV System.jpg
Image


:link: http://www.corvair.com/user-cgi/catalog ... ow_page=60
Image

Part number C1176: PCV VALVE

Weight: 0 lbs 4 oz
Catalog Pages(s): 60(13)
Price: $ 8.95


If you have the correct PCV valve and it is installed properly and tests correctly (following the procedures in the shop manual supplement), you may have a situation where the engine is producing excessive blow-by into the crankcase and is overwhelming the PCV system. Have you run a compression test on the cylinders to check the condition of the piston and rings?

:chevy:
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1962-1963 Supplement - Chevrolet Corvair Shop Manual - Section 7 - Engine Tune-Up.pdf
1962-1963 Supplement - Chevrolet Corvair Shop Manual - Section 7 - Engine Tune-Up
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Bard Beach
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Re: Blow by smoke through the PCV system

Post by Bard Beach »

64powerglide wrote:Are you getting any white exhaust smoke?
No exhaust smoke..



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Bard Beach
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Re: Blow by smoke through the PCV system

Post by Bard Beach »

Trip wrote:Did your PCV valve come from a Corvair supplier?

I know my FLAPS gave me the wrong one and I believe it caused the same kind of problems you describe. I personally prefer a road draft tube to avoid any possible issues. Alternatively I have used the later model Corvair PCV that has an orifice instead of a PCV valve.

The biggest common mistake with Corvairs is venting the PCV to the engine room, Jay Leno's Yenko Stinger is set up this way, as was my Corsa at one time. The problem is that the heater system then pumps the blowby into the passenger compartment. Maybe Jay Leno's Stinger doesn't have a heater setup installed at all.
It was a used one from a Corvair mechanic. It's possible that it might not be the right fit..




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Bard Beach
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Re: Blow by smoke through the PCV system

Post by Bard Beach »

bbodie52 wrote:The Positive Crankcase Ventilation (PCV) system was designed by engineers to deal with crankcase ventilation requirements in a wide range of engine operating conditions — full throttle, closed throttle, partial throttle, high RPM, low RPM, and everything in-between. The baffle plate and vents, the PCV tube, the PCV valve or fixed vacuum orifice that is connected to the engine intake, and the PCV breather connected to the air cleaner, are all part of a dynamic system design that is intended to function continuously during all engine operating conditions.

1962 and earlier Corvair engines did not have a PCV system. Like most earlier engines, they were fitted instead with a simple road draft tube.
Image
Image
Image

When road draft tubes were used, they were simple unfiltered tubes that routed from the Corvair crankcase cover directly downward, where they vented through a hole in the sheet metal cover under the right side of the engine, adjacent to the oil pan. There was never a tee on it that connected via an orifice to manifold vacuum at that time. The first stage of Positive Crankcase Ventilation that appeared around 1963 utilized an appropriately-sized vent restriction (PCV valve design AC-CV584) that limited the amount of crankcase fumes and air that could be drawn into the vacuum balance tube that connected at the base of the carburetors to the intake manifold. This was essentially a "vacuum leak" that was engineered into the system to draw some of the crankcase fumes into the intake manifolds to be burned as they passed through the combustion chambers and ultimately out through the engine exhaust system.

Part of the main vent tube is ALSO CONNECTED TO THE AIR CLEANER. This allows those excess crankcase pressures that cannot be completely drawn through the PCV valve and into the intake manifold to be managed by instead having them drawn through the air cleaner assembly and into the carburetor intake throats. The secondary vent path into the air cleaner assembly allows for excess crankcase pressures that routinely occur at higher engine speeds and that would also routinely overwhelm the limitations of the PCV valve vent path. (This necessary connection also allows air that is filtered by the air cleaner air filter to access the engine crankcase, providing a balancing effect for the crankcase so that crankcase vacuum and pressure can be maintained at approximately normal atmospheric pressure). Without the connection to the air cleaner assembly, the sealed crankcase has no way to "breathe", because half of the normal PCV system design would have been omitted.

The fixed orifice only became a part of the PCV system in 1964-1969. The use of a fixed orifice was not a part of the 1964 system in Forward Control (FC) vehicles and in air conditioned cars, because of clearance limitations in the van and truck engine compartments and in cars equipped with air conditioning. Those vehicles retained the earlier design of the air cleaner assembly with its associated PCV valve design (AC-CV584).

All PCV systems have connection between the main vent tube and the air cleaner, which is necessary for proper crankcase ventilation. With the use of custom individual air cleaners, you can replicate the portion of the PCV system that is missing by installing a connection to the right air cleaner. The custom air cleaner can be modified to provide a hose connection at its base.
1963 PCV System.jpg
Image


:link: http://www.corvair.com/user-cgi/catalog ... ow_page=60
Image

Part number C1176: PCV VALVE

Weight: 0 lbs 4 oz
Catalog Pages(s): 60(13)
Price: $ 8.95


If you have the correct PCV valve and it is installed properly and tests correctly (following the procedures in the shop manual supplement), you may have a situation where the engine is producing excessive blow-by into the crankcase and is overwhelming the PCV system. Have you run a compression test on the cylinders to check the condition of the piston and rings?

:chevy:
Wow thank you for all of this!!
Reading up on this all now, very helpful!




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Re: Blow by smoke through the PCV system

Post by 64powerglide »

Post a photo of your engine compartment!!
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MonzaJoshAZ
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Re: Blow by smoke through the PCV system

Post by MonzaJoshAZ »

I am curious if you had a fix to this problem. (hoping it is something simple)
I have the exact same issue that you originally described. Car runs great when cold weather out but sputters a little when it is hot out and I give it too much pedal. I have to back off on the pedal and the acceleration a bit and just accelerate a little slower so that I don't get the puttering.

While engine running, I took the air filter off and noticed a small amount of smoke (or what looked like vapor type smoke) coming from the PCV valve tube into the air filter.

Just wondering if you found a solution.
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Re: Blow by smoke through the PCV system

Post by bbodie52 »

:welcome2: :wave: :wave: Welcome to the Corvair Forum!
MonzaJoshAZ wrote: » Sun May 02, 2021 2:21 am

...Car runs great when cold weather out but sputters a little when it is hot out and I give it too much pedal. I have to back off on the pedal and the acceleration a bit and just accelerate a little slower so that I don't get the puttering...
A similar description could be applied to engine DETONATION that can occur with an engine that makes a "rattling" sound under load or hard acceleration, perhaps while climbing a hill or with a fully-loaded car on a warm day. An intake vacuum leak can cause a lean fuel/air mixture. Poor, low octane gasoline, too much timing advance, etc. can cause the engine to be marginal under light loads or when cool, but to advance into detonation (fuel exploding rather than burning) with a warmer ambient temperature, hotter engine, etc. Detonation surfaces as a rattling sound when applying heavy throttle. Are you using PREMIUM, high octane gasoline, or REGULAR or MID-GRADE gasoline? Have you checked the dwell (ignition points gap)? A change in dwell as the ignition points wear can affect ignition timing. A vacuum leak can cause a lean fuel/air mixture which can cause an engine to detonate. See if some tune-up work or increasing the octane rating of your fuel helps.

It is normal for some crankcase smoke (fumes) to be seen coming from the PCV tube as blowby fumes collect in the sealed crankcase and are vented through the PCV system, to be reburned via the carburetor intake system. But excessive blowby can be an indication of poor control and possibly excessive wear of the rings or cylinder walls. A compression test may reveal the condition of the seal between the combustion chambers and the engine crankcase.

The link below will provide you with a list of useful websites that are Corvair-related. Some of the links will lead you to an extensive technical library that will allow you to download shop manuals and other technical references in Adobe Reader format at no cost. There is also a link that will help you to locate nearby CORSA (Corvair Society of America) club chapters. You will also find a list of essential Corvair parts suppliers. Clark's Corvair Parts in Shelburne Falls, MA is the biggest and oldest Corvair supplier in the world. You will find a link that can provide you with a series of videos that amount to a tour of the Clark's Corvair Parts facilities. Parts suppliers such as this truly make our Corvair hobby possible.

Common and Useful Corvair Websites

Corvair Forum :link: viewtopic.php?f=225&t=6007

:dontknow: I would like to encourage you to expand on your initial post and tell us more about yourself, your mechanical knowledge and experience, your Corvair interests, and your goals for your Corvair. Helping us to know more about you will help us to write comments to you that are tailored to your needs and experience. Detailed pictures of your Corvair — including the engine compartment — would possibly be useful. Knowing your city location may suggest some helpful nearby support, such as a local Corvair owner's club chapter. If there is a local CORSA (Corvair Society of America) club chapter near you, joining such a local Corvair group may be a big help in getting answers and recommendations that would be useful to you. (There are CORSA club chapters in the Phoenix and Tucson areas).
Image

Image
Cactus Corvair Club Mesa, AZ (Phoenix area) :link: https://www.cactuscorvairclub.com/
While a salesman at Rudolph Chevrolet in Phoenix Arizona, Lou Grubb decided there were possibilities in an inexpensive, economy car produced by the Chevrolet Division, the Corvair. He sent letters to recent Corvair buyers and devotees alike inviting them to a social dedicated to appreciation of the car. With a promising response, discussion turned to organizing a new sports car club. With hasty planning, the first event was an economy run put together by a group of rookie enthusiasts who later became the first members of Cactus Corvair Club after its Constitution was signed in October 2, 1963.

We are the oldest, continually active, Corvair club in the world!

As part of the Phoenix Chapter of CORSA (Corvair Society of America) we hosted our first regional mini-convention in April of 1976. People from all over the country came, with an estimated 90 cars and 150 people attendees. The event included autocross, a concours show, driving tour of the Valley of the Sun, and a “Fiesta banquet. The Cactus Corvair Club hosts an annual All-Corvair show in early October, participates in classic car shows throughout the year (usually benefiting local charities), and supports classic car events, museums, and organizations dedicated to the preservation and public education of our automotive history. We are a community of car enthusiasts; all our events are family oriented and we are excited to meet you.

With the closing of Lou Grubb Chevrolet / Power Chevrolet dealerships, the Cactus Corvair Club moved to Thorobred Chevrolet in Chandler.

In 2016, the Thorobred Chevrolet dealership was sold to Earnhardt Auto Centers and is now Earnhardt Chevrolet Chandler. We hope for many more years of working with the new owners to promote the Corvair legacy as well as all the new Chevrolet offerings.
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Tucson Corvair Association Tucson, AZ :link: http://www.corvairs.org/
FACEBOOK :link: https://www.facebook.com/TucsonCorvair/?ref=profile
The Tucson Corvair Association meets on the third Tuesday of every month in conjuction with the Classic Chevy Club of Tucson at 6pm. Quarterly TCA business meetings are held on the thrid Tuesday of January, April, July, and October at 6:30pm. We meet at:

Crown Concepts
3930 W Costco Drive
Marana, Arizona
(near Orange Grove and Thornydale)

These quarterly meetings are only a few minutes long to discuss TCA-specific business. Our regular monthly meetings are held in conjunction with the Classic Chevy Club of Tucson which meets every third Tuesday at 6pm at Crown Concepts.
:welcome:
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible
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