Internal part of crankcase vent tube

[Jeremy Hedges]

I have a '65 327 L-79 that I am putting together. My question is on the internal part of the crankcase vent tube assembly. I am not sure what the official name for it is, but it is the cannister/tube that is pressed into the top rear of the block. someone told me that it was pre PCV. I have the part, but I was told that it had some metal mesh inside of it. Mine does not. Does it need to be in there? If so what can I use, where can I get it.
Thanks
Jeremy

[Clem Z.]

Re: Internal part of crankcase vent tube

i have never seen any mesh in the "can" as it is there to seperate oil from the oil vapor.

[Duke W.]

Re: Internal part of crankcase vent tube

GM calls it a "ventilator" - 3728502 - and as Clem said, it functions as a liquid vapor separator. Your engine should have one to keep it from ingesting oil through the PCV system. I don't know if it is still available through GMPD or in repro, but it was used on all SBs from 1955 to 1967 including those with road draft tubes and those with PCV systems. Any pre-'68 block - those with a crankcase ventilation port next to the distributor bore - should have this item in the lifter valley, so you can probably find one in a junkyard that still has a lot of pre-'68 engines and parts.

Duke

[John H.]

Re: Internal part of crankcase vent tube

Paragon and LICS have them - reconditioned - about $35-$40.

[Jeremy Hedges]

Re: Internal part of crankcase vent tube

so the can is empty? just tubes?

[John H.]

Re: Internal part of crankcase vent tube

Jeremy -

The can just has a couple of sheet metal baffles in it to keep the liquid oil in the engine and allow only vapors to pass through it; it's the "intake" point (from the clean side of the air cleaner, through a flame arrestor) for the crankcase ventilation system, and the baffles keep oil from being blown back into the air cleaner.

[Tom H.]

Re: Internal part of crankcase vent tube

Also- the mesh that you may be referring to is at the air cleaner end of the draft tube (inside the air cleaner) and it's functionally a flame arrestor to keep backfires from flashing into the crankcase with obvious potential consequences. The airflow goes through the air cleaner, down the draft tube, through the crankcase, to the lifter valley, to the suction port on the oil fill tube and finally the flow is aspirated into the carb base by full manifold vacuum. The flow rate is governed by a fixed orifice or PCV valve depending on the performance set-up of the engine.

[Tom Parsons]

Re: Internal part of crankcase vent tube

As mentioned, this canister is used (and required) on ALL SBs, 55-67. Beause this was installed on untold thousands of engines, you should be able to pick up one almost anywhere. The price that is asked for a reconditioned one is ridiculous! They did NOT have any mesh in them, but, I did install mesh in one of the canisters for an engine I built a few years ago. I went to a restaurant supply and purchased a stainless mesh pad used for scrubbing pots/pans. I carefully drilled the 4 spot welds on the end cap of the canister, stuffed in as much mesh as I could, then had the cap welded back in place. I can't tell if it made any difference, but it's done.