PCV for early engine

[Terry Plata]

My '57 (single carburetor, with powerglide) puffs a small amount of smoke from the road draft tube during hot idle. Can I add a PCV valve and eliminate the road draft tube? Any valve part numbers and suggested routings would be appreciated. Thanx! Terry

[Mike M.]

Re: PCV for early engine

get the plumbing off a 63 chevy vette or pass car small block. why not just stuff a tampoon up the road draft tube? only kidding(don't know how to make happy face). mike

[terry plata]

Bulging valve covers

Thanks Mike, The plug should work just fine, until the crankcase pressure blows the valve covers off! ha ha. I think the '63 PCV system you refer to has a hole in the valve cover and one in the air cleaner base. Taboo on my car! I need a system that is more discrete. Any other ideas? Terry

[Tracy C.]

Re: Bulging valve covers

No hole in 63 valve covers. I think Mike is refering to the plumbing that comes out of the back of the block near the distributor to the base of the carb.

Mikie.. is made by typing a colon : and then a captial D

Type these next to each other with at least one space before and after the series.

tc

[Paul L.]

Re: PCV for early engine

Could you adapt a 1967-style oil fill tube PCV? The crankcase vent attaches to the base of the air cleaner (large black hose) to complete the pressurized circuit. (Sorry about the Edelbrock! My 4160 Holley went bad recently and is being rebuilt.)

[Duke W.]

Re: PCV for early engine

A proper PCV system for a carbureted engine needs a valve designe to both meter flow and act as an anti-back device to prevent a backfire from propagating to the crankcase and causing an explosion. The system also needs a fresh air inlet and the "breather" type oil cap will suffice.

The PCV outlet can be routed from the block vent where the road draft tube currently resides through the valve and to the inlet manifold. You should take a look at the '61-'62 system that was required on CA cars. I'm not sure where the flow path entered the inlet manifold.

For '63, the first year that all cars sold in the US had PCV, the AFBs had a inlet (1/4 NPT IIRC) in the back of the carb for the valve, which was attached with a 90 degree adapter. Internally this port communicated with manifold vacuum at all times. I believe the WCFB on the 250 HP engine also had a port in the WCFB for PCV, but your earlier WCFB probably does not. The vent hole in the back of the block has an adapter to mount a metal pipe and the outlet of the pipe connects to the valve with a short piece of rubber hose. You should review the configuratations of these PCV systems in the applicable year AIMs.

A valve from an early 283 or 327 should suffice, but your biggest problem will probably be finding a location for the manifold inlet.

PCV is an excellent idea that will both improve crankcase ventilation, which will reduce oil dilution and reduce total HC emissions by 20-30 percent, but it must be properly engineered.

Duke

[terry plata]

Re: PCV for early engine

Duke and others, OK, I can remove the road draft tube and fashion an adaptor plate with fitting to accept the PCV valve, no problem. You are correct that getting into the intake manifold or into the base of the early WCFB may be a challenge, but I will work on that as I can still make the retrofit unobtrusive. Now the rest of the story. The PCV valve will be active during hign intake manifold vacuum (idle) but typically drops out at low vacuum (at speed). This situation is normally remedied with a hose in the air cleaner housing going to a valve cover. Really don't want to drill a valve cover. If you feel this hose is necessary, how about picking up the oil filler tube per later car? Terry

[Duke W.]

Re: PCV for early engine

A fresh air inlet is absolutely necessary, and the pre PCV "breather" type oil fill tube cap - same as typically used with road draft tubes - will suffice.

A PCV valve for a small block of the era will properly meter air flow under all vacuum conditions. During high vacuum the valve closes down to restict air flow. At low manifold vacuum the valve restriction area is reduced to maintain flow.

Duke

[Dick W.]

Re: PCV for early engine

Duke, iffen my memory serves me correctly, there was an aftermarket kit to convert these cars with road draft tubes to positive crankcase ventilation. Maybe this will jog some of the real old timers memory (you see I was only one when the '62 came out ). I am not sure who made the thing, but I was working in a dealership parts department during this era and remember seeing/hearing of the kit.

[Duke W.]

Re: PCV for early engine

Wouldn't be a bit surprised if even Chevrolet made some kind of kit for at least some engines, but that was long before I started collecting P and A manuals.

Maybe Joe L. can come up with a number, but no doubt it's long since discontinued.

PCV architecure for a carbueted engine is fairly simple. As long as one realizes that a fresh air inlet is required, along with a metering valve with anti-backfire provision and a manifold vacuum source, a reasonable amount of creativity should allow anyone to design a functional and safe PCV system.

Duke