Oil loss

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Leverone
Posts: 4
Joined: Sun Jun 25, 2017 1:55 pm

Oil loss

Unread post by Leverone » Fri Sep 22, 2017 8:21 am

New member from California here. I have two 1963 Spyder convertibles. I just replaced the entire braking system, hard lines and all, as well as springs and shocks and new radial tires on one. It runs great, rides and drives great. Having lots of fun. The oil pan used to leak terribly, clearly had hit a parking stop or something. I changed it to a Clark's aluminum pan and put their silicone gaskets on the pan and valve covers. Now after a drive there is just one or two drops of oil that drip from the transmission. I will get to those. But every time I drive it I noticed light oil smoke coming out the hood vents after shutting off and hot. It seems to be oil coming out the dipstick tube and running down onto hot bits. Not enough to form as drips anywhere. Oil is not overfilled. Anyone have any suggestions? Thanks.

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bbodie52
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Re: Oil loss

Unread post by bbodie52 » Fri Sep 22, 2017 11:51 am

:wave: :welcome2: Welcome to the Corvair Forum!
Leverone wrote:Fri Sep 22, 2017 10:21 am

... every time I drive it I noticed light oil smoke coming out the hood vents after shutting off and hot. It seems to be oil coming out the dipstick tube and running down onto hot bits. Not enough to form as drips anywhere. Oil is not overfilled. Anyone have any suggestions? Thanks.
If oil is being forced out of the dipstick tube, it sounds like you either have a problem with excessive crankcase pressures caused by excessive blow-by that leaks past the pistons and piston rings into the crankcase, or you may have a problem with your Positive Crankcase Ventilation (PCV) system. The engine crankcase is a sealed chamber. It is normal for a certain amount of combustion chamber gases to escape past the piston rings and into the engine crankcase. Those fumes are expected and on 1963-1969 Corvair engines they are vented from the crankcase and drawn back into the intake system via a vacuum tube and a tube that connects to the air cleaner. This system is designed to properly ventilate the sealed crankcase during all engine operating conditions and speeds. If the PCV system becomes clogged, or if the piston rings and cylinders become excessively worn, the crankcase pressure buildup may exceed the ability of the PCV system to properly vent the engine crankcase. Under these circumstances the pressure buildup will seek a path out of the crankcase. The only path readily available is often the oil dipstick tube. As the pressure pushes its way through the oil dipstick tube, engine oil is often siphoned from the oil reservoir at the bottom of the crankcase and pushed up through the dipstick tube. A small volume of oil siphoned in this way would exit the top of the dipstick tube and likely drain back the outside of the engine and create a mess around the right exhaust manifold. If pressures become too great oil may be forced out of the dipstick tube at such a rate that it will be spraying around the engine compartment and making a mess in that area.

What follows is an explanation of the PCV system, and the variation of that PCV system that should be installed on your turbocharged engine. I would suggest starting by a examining the PCV system and cleaning it as necessary to ensure that it is fully functional. If cleaning your PCV system and confirming that it is properly connected to your turbocharger and air cleaner does not resolve the problem, you may need to perform a compression check of all cylinders to check the condition of the seal that should exist in each cylinder. A proper seal is affected by the condition of the pistons and cylinder walls, piston rings, intake and exhaust valves, and cylinder head gasket. If you find one or more cylinders that fails the compression test, a more advanced cylinder leak down test can be performed to try to determine the specific cause of the low cylinder pressure. Hopefully a simple cleaning and servicing of the PCV system will resolve your problem. A failure of a cylinder compression test and/or leak down test could point to the need for a more extensive engine overhaul or repair.

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.
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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.

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The illustration below shows the proper configuration for the turbocharged Corvair PCV system. The illustration was taken from the Corvair shop manual.

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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.

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. While the Corvair Forum can be very helpful as you work on your Corvair, having local friends and contacts in your region who are knowledgeable about the Corvair can also be very helpful. These family-friendly CORSA chapters often offer picnics, group scenic drives, technical training and assistance, car shows, and competition events that can greatly enhance your enjoyment of Corvair ownership. You will also find a list of essential Corvair parts suppliers. Clark's Corvair Parts 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. I think you will be amazed at the quality of the reproduction components they offer — particularly the interior carpeting and re-upholstery items. Parts suppliers such as this truly make our Corvair hobby possible.

Common and Useful Corvair Websites

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

I have attached copies of Corvair shop manual supplements to the 1961 Shop Manual. They include supplemental information that applies to the turbocharger system that was introduced in 1962. However, the 1962-1963 supplement does not fully address the turbocharger PCV system. Additional information was provided in the 1964 supplement, which I have attached.

:chevy:
Attachments
1962-1963 Supplement - Chevrolet Corvair Shop Manual - Section 6a - Engine.pdf
1962-1963 Supplement - Chevrolet Corvair Shop Manual - Section 6a - Engine
(1.26 MiB) Downloaded 2 times
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
(899.84 KiB) Not downloaded yet
1964 Supplement - Chevrolet Corvair Shop Manual - Section 7 - Engine Tune-Up.pdf
1964 Supplement - Chevrolet Corvair Shop Manual - Section 7 - Engine Tune-Up
(931.65 KiB) Downloaded 2 times
1962-1963 Supplement - Chevrolet Corvair Shop Manual - Section 9 - Fuel & Exhaust Systems.pdf
1962-1963 Supplement - Chevrolet Corvair Shop Manual - Section 9 - Fuel & Exhaust Systems
(3.83 MiB) Not downloaded yet
1964 Supplement - Chevrolet Corvair Shop Manual - Section 9 - Fuel & Exhaust Systems.pdf
1964 Supplement - Chevrolet Corvair Shop Manual - Section 9 - Fuel & Exhaust Systems
(3.99 MiB) Downloaded 2 times
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

Leverone
Posts: 4
Joined: Sun Jun 25, 2017 1:55 pm

Re: Oil loss

Unread post by Leverone » Mon Sep 25, 2017 1:15 pm

THANK YOU! This will be very helpful. I suspected a crankcase ventilation issue but being new to Corvair's wasn't sure where to start looking. This is very much appreciated.

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