cor66vette

The original set up for the '66 327/350 re: oil filler tube and filler cap is composed of a sealed cap on a filler tube with a pcv valve connected to the carb via hose. I am thinking of changing my present set up (not original- carb is plugged and the oil filler tube is without accommodation for a pcv valve and the filler cap is a breather).

Can anyone advise the benefits of either set up? The car runs fantastic as is - should I risk performance for "original"?

Thanks for your help. :cheers:

Mac

SWC Duke and JohnZ weighed in on this topic a while back, if I remember correctly. Maybe you can find that thread through the 'search' forum?

As long as the crankcase pressure has a way to be relieved, everything's going to work properly. The closed system (crankcase pressure relieved through pvc valve into carb) is better because you're controlling where the oil & fuel laden fumes go.

JohnZ

A functioning PCV system ventilates the crankcase by drawing in outside air, passing it through the engine, and exhausting the vapors through the PCV valve (which meters the flow rate), and then inhaling them through the carb base into the intake and burning them; this is a positive-flow closed system. In your case, as originally designed, the outside air intake is through the clean side of the air cleaner through a hose and steel tube into a hole in the back of the block; the "exhaust" side is through the oil filler tube, PCV valve and hose to the large fitting on the carb base. If you now have an oil fill tube with no PCV connection to the carb and just a breather cap, you'll have no circulation of air through the crankcase (no "ventilation"), as nothing is "pulling" fresh air and hot oil vapors through the engine. All you'll have is pressure relief, where crankcase pressure will blow hot oil vapors out of the intake pipe at the rear into the air cleaner, and out of the open breather cap on the oil fill tube, all over the top of your engine. This becomes a safety issue as well, as the hot oil vapors are combustible, and a carb backfire can result in an air cleaner and/or crankcase explosion. The PCV system is there for a reason, and does NOT compromise performance - I'd recommend keeping it; you could either swap out the oil fill tube for the correct one with a PCV provision (and put the PCV valve and hose to the carb back on) and a sealed cap, or add a PCV valve in one of the valve covers (as later cars have) with a hose to the carb :cheers:

cor66vette

Thanks for getting back to me- it sounds like I'm better off with the original set up. :cheers: