Balance Tube Fittings 140 - Change?

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GasDaddy140
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Balance Tube Fittings 140 - Change?

Unread post by GasDaddy140 » Tue Jul 11, 2017 8:36 pm

Hi Corvairs!

I'd like to know how to delete the left side tube fitting. I believe the right side is for a Corsa vacuum gauge, which I will utilize. Can I block off the other without ill effects? I plan on running individual air cleaners, chrome bells. Does one use fat radiator hose to make an adapter for the clamps? I'm not buying Clark's kit stuff.

Thank you!
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Alan Duquette
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Re: Balance Tube Fittings 140 - Change?

Unread post by Jerry Whitt » Tue Jul 11, 2017 9:11 pm

Local auto parts store should have rubber caps for less than a dollar.
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terribleted
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Re: Balance Tube Fittings 140 - Change?

Unread post by terribleted » Tue Jul 11, 2017 9:47 pm

What are you using for your PCV system? That is what goes on the larger port. Should be hosed to the smaller nipple (orifice) on the pipe that goes from vent tube to stock aircleaner base
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Re: Balance Tube Fittings 140 - Change?

Unread post by bbodie52 » Wed Jul 12, 2017 7:14 am

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Jerry Whitt wrote:Mon Apr 14, 2014 11:13 pm

The letters PCV are short for "Positive Crankcase Ventilation"

As the engine runs, some of the explosion of air and fuel above the piston actually blows by the rings. This in turn, can pressurize the crankcase, causing oil seals and gaskets to leak.

To help stop the pressure build up, many older cars used a vent tube to just allow the pressure to escape into the atmosphere.

As the rings wear, more and more pressure leaks by the rings, and more and more fumes were vented to the atmosphere.

Somebody came up with an idea. Suppose that the fumes were recirculated into the combustion process. Maybe better fuel economy? The idea took hold, and various smog people thought this process may help the environment also. Basically, the vented fumes are placed in a hose that goes back to the base of the carburetor. Another problem then came about, an air fuel ratio problem for the carburetors.

Aha! Suppose a valve that helps control the flow is used?

Under high vacuum readings, the valve allows a small volume. Under low vacuum readings, (usually higher engine speed) more fumes flow.

My two 1965 Corvairs do not have PCV valves, but use a tube running between the base of the carburetors and hooked to a crankcase breather with a calibrated vent hole.


Jerry Whitt
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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 vacuum balance tube, 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.

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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.
UNSAFE wrote:Tue May 14, 2013 1:35 pm

Oil is forced out the dipstick tube by excess crankcase pressure - Period . This can be from that funky PCV setup or simply too much blowby caused most likely by leakage between the rings and cylinder.

Simply venting the case does very little — think about this, Atmospheric pressure is about 14.7 pounds per square inch. This means that you will have at least 14.7 pounds of pressure inside your motor before any outward flow begins . You need a functioning PCV system to cause a pressure differential.

Ideally you want no pressure in your motor — it will prevent the rings from seating properly. Much of the rings outward force is caused by the combustion and compression pressure pushing outward against the rings thru the relief slots or holes in the ring grooves.

Many drag racers use a belt driven vacuum pump to create the vacuum . Remember that the PCV system is much more than a pollution control device. It was being used on many things way before there were any smog requirements. On my engine I use a vacuum setup that is driven by the exhaust system. It creates the lower case pressure that I want for proper ring sealing. If I remove my oil fill cap and hold a strip of paper over the tube it will suck the paper into the engine. I also use total seal gapless rings.
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GasDaddy140
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Re: Balance Tube Fittings 140 - Change?

Unread post by GasDaddy140 » Thu Jul 13, 2017 11:37 am

Thank you guys for the help and education! I know what I'm going to do. I'll utilize the correct small ports for the crankcase and balance tubes line. Instead of having a vent tube into the stock air-cleaner (which I'm not using) I'll run a breather outside of the engine compartment.
Alan Duquette
Rohnert Park, CA
"When in doubt...Hit the gas!" A.J. Foyt.

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1971 Dodge Sportsman "shorty" 318 van
2015 Nissan Juke S

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Re: Balance Tube Fittings 140 - Change?

Unread post by bbodie52 » Thu Jul 13, 2017 2:15 pm

This is a common problem that is fairly easy to solve. The first couple of pictures below show the 140 hp engine with custom air cleaners that I set up back in the early 1980s. I simply ran a single hose to a connector that was mounted on the bottom of the right air cleaner. A variety of adapters are available in local auto parts stores and on the Internet. A couple are shown at the bottom of this post. I would recommend that you try to replicate the original design as closely as possible. The fixed orifice tube and connection to the vacuum balance tube can be easily retained. The only modification needed is a connection to the custom air cleaner, which provides a secondary path that is inherent in the design for crankcase fumes to pass through the carburetor. This connection also provides for filtered air to be drawn into the crankcase, as needed.
Custom PCV Connection.jpg
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Relieve excess pressure with these Edelbrock crankcase ventilation hose connection kits. These replacement kits come complete with everything you need to mount the adapter to your air cleaner to complete your crankcase ventilation system and keep it working as it should. Don't let your car suffer because of a weak link, replace it with one of these Edelbrock crankcase ventilation hose connection kits
:link: https://www.summitracing.com/parts/edl- ... 10EALw_wcB
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Universal Air Cleaner Smog Vent Tube Fitting - Filter Base To Valve Cover PCV
:link: https://www.amazon.com/Universal-Cleane ... G3BRDXT79W
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Re: Balance Tube Fittings 140 - Change?

Unread post by 66vairguy » Fri Jul 14, 2017 1:29 pm

Brad is correct. A correctly operating PCV system has no negative affects on the engine and it eliminates a major source of air pollution.

The PCV system was designed by GM for military engines to keep water out of them during water maneuvers. During evaluation it was found that crankcase emissions were far greater than exhaust (tail pipe) emissions. This study eventually brought about the modern PCV systems in part to keep engine smells out of higher end vehicles, although cleaning up the air became the primary motivation.

I have a pair of air cleaners and mounted a PCV vent hose connection on one side like Brad. Some of the little single chrome air cleaners have a port to install the PCV hose.

To ensure proper function of the "fixed orifice" PCV port you must connect one path to the air cleaner to allow excess fumes to be pulled into the air cleaner, or fresh filtered air to be pulled from the air cleaner into the balance vacuum tube due to variations in crankcase gas volume.

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Re: Balance Tube Fittings 140 - Change?

Unread post by acarlson » Tue Jul 18, 2017 2:54 pm

Since this topic turned a PVC discussion, I have a question. My Corsa turbo does not have a complex PVC arrangement. A rubber tube from the crankcase cover runs into a nozzle on the air cleaner. Is that the stock arrangement for a 65 Corsa Turbo ? There is no PVC valve anywhere in the path...

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Re: Balance Tube Fittings 140 - Change?

Unread post by 66vairguy » Tue Jul 18, 2017 3:36 pm

Few Corvairs used the PCV (Positive Crankase Ventilation) check valve popular on other Chevy engines. On the 65 Corvair the more common "metered orifice" that is in Brad's Fig. 11 was used. It must be cleaned (every tune-up) or it will get restricted with "gunk". Bascically the orifice meters in SOME crankase vapors depending on manifold vacuum (the carbs were built to allow for this).

The hard part to understand is this: If the crankcase fume volume to the vacuum cross tube exceeds what the orifice will allow then the excess goes to the air cleaner and into the carburetor(s) inlet (you don't want to vent this to the engine compartment since the fumes contain carbon monoxide and will end up in the heater system when the heater is on - not good). When the crankcase fume volume is less than what the orifice will allow then air comes FROM the air cleaner to prevent a vacuum forming in the hose and of course a reduced airflow to the vacuum cross tube will result in a richer idle mixture.

It's a simple system the ingests crankcase fumes into the engine via the vacuum cross over or the air cleaner and maintains a constant ambient air pressure at the intake to the orifice so as not to vary the idle fuel mixture.

Contrary to old myths started when early Calif. systems were poorly installed, the factory PCV systems have no impact on performance or driveability IF the engine is in good order. A worn engine with a lot of blow-by will overload and plug up the PCV system.

I've pulled off PCV pipes from worn out engines that were plugged solid with "gunk".

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Re: Balance Tube Fittings 140 - Change?

Unread post by bbodie52 » Tue Jul 18, 2017 6:05 pm

acarlson wrote:Tue Jul 18, 2017 4:54 pm

Since this topic turned a PVC discussion, I have a question. My Corsa turbo does not have a complex PVC arrangement. A rubber tube from the crankcase cover runs into a nozzle on the air cleaner. Is that the stock arrangement for a 65 Corsa Turbo ? There is no PVC valve anywhere in the path...
Getting back to your original question about a PCV arrangement on a 1964-1966 turbocharged Corvair, the illustration below shows the proper configuration for the turbocharged Corvair PCV system. The illustration was taken from the Corvair shop manual.

The turbocharged Corvair PCV system is functionally the same as that used on non-turbocharged, normally aspirated Corvairs. A short tube from the metered orifice is connected directly to the turbocharger intake at the base of the carburetor. This would be the correct connection point since it would always be a source of unpressurized intake vacuum. The other portion of the PCV tube connects to the air cleaner, as it does on the normally aspirated Corvairs.
PCV System Layout (Turbo).jpg
Turbo PCV System.jpg
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Re: Balance Tube Fittings 140 - Change?

Unread post by acarlson » Wed Jul 19, 2017 3:47 am

Brad, Thanks - I got that setup. What I didn't realize till I saw your pictures was that there is supposed to be a clamp holding the crankcase breather tube and the PVC tube together. I don't have that (I'll need to contact Corvair Ranch).

Also there are 2 air connectors on the turbo air cleaner. The large one matches your PVC diagrams. There is a smaller one next to it. Where does the smaller one go ?
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Re: Balance Tube Fittings 140 - Change?

Unread post by bbodie52 » Wed Jul 19, 2017 11:01 am

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acarlson wrote:Wed Jul 19, 2017 5:47 am

...there are 2 air connectors on the turbo air cleaner. The large one matches your PVC diagrams. There is a smaller one next to it. Where does the smaller one go?
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It appears that the large tube is for PCV, and the smaller tube is part of the choke system (CHOKE CLEAN AIR TUBE). The picture is from page ENGINE FUEL 6M-12, out of the 1965 Corvair Chassis Shop Manual (attached).
Turbo Choke Clean Air Tubes.jpg
Turbo Choke Clean Air Tubes
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