Oil filler Cap

[Roger W.]

I just noticed in the Corvette Central Catalog that the oil filler cap for solid lifters is non vented and for hydraulic lifters is vented. What is the reason for this?

[Duke W.]

Re: Oil filler Cap

I recall reading that Chevrolet wrote a TSB that recommended replacing the vented oil cap with a non-vented type to address customer complaints about "oil misting" inside the engine compartment.

At high revs there is a "hurricane" inside the crankcase that forms an oil-air emulsion, and if pressure becomes slightly positive, even a few inches of water, this emulsion will be pushed out of any available opening, and this is more likely on high revving mechanical lifter engines, especially if they are run hard.

This situation is best addressed by implementing the '61-'62 PCV system required for cars sold in California that will more efficiently purge blowby from the crankcase and return it to the inlet system for subsequent combustion. This will significantly increase oil life, lower fuel consumption, and reduce the major source of HC emitted to the atmosphere.

There is no downside to a PCV system.

Maybe someone has a digital copy of the TSB they can post.

Duke

[Joseph L.]

Re: Oil filler Cap

Duke, you are correct about the non-vented breather cap. I get a lot of crud on the front of the carb and engine when I have fun on the road and I use the vented cap for better crankcase ventilation. Here is TSB 253: Sep 28, 1956. It is also in the 1956-57 JM.

Joe

[Roger W.]

Re: Oil filler Cap

Thanks Duke and Joe. I have a vented cap now with solid lifters.