The Stovebolt Site Forums The Shop Area Engine Shop PCV Kit Installation on 1955.1 235 truck engine

These photos cover the installation of a genuine GM-approved AC brand PCV kit issued and fitted to my signature 1955 1st Series 3100 in 1972 to fulfill California (CA) emission control requirements in effect at the time. This truck today still has the original ‘54-Early ‘55 235 engine (casting date September 1954). The PCV kit was purchased over the counter from a CA Chevy dealer in 1972. Later, CA exempted 1974 and earlier vehicles from emissions test compliance. The PCV system was left installed on the 55.1 truck and remains functional today.

The first photo shows the core plug (included in kit) installed in lower right front of the engine block after the road draft tube was removed.

The remainder of assorted photos show details of the PCV system installation.

All components necessary for the PCV system installation plus instructions were included in the AC kit: PCV valve (AC part number CV-609C), hoses, fittings, core plug for the block, sheet metal screws and non-vented oil filler cap. The four small vents on the valve cover were sealed shut.

I think the photos are self-explanatory but if questions, I’ll try to address.

I like it…a lot.

See attached pic of my setup. Ignore the cobbled up temporary fuel line loop. That has since been adressed with a new steel line. But my PCV still looks much the same. Clean makeup air is via a clamp on breather attached to the bottom of the road draft tube.

My “version 2.0” plan was to use a non vented breather with a PCV tube, plumb a threaded PCV into the manifold fitting, and run some nice looking steel line in a fairly inconspicuous manner.

But no matter what, I’d end up with an octopus of lines at the front of the valve cover, between the PCV, the fuel line, and vac line.

Having seen yours….i think I could do something very similar. Perhaps get a valve cover with the centered breather hole, and then more or less replicate the plumbing you have. No welding or cutting or riveting…still looks fairly low key and stock-ish.

One additional photo showing complete PCV system installation, left side of engine.

Is there a baffle inside the valve cover on the “suck” side of the system?

There's probably not enough oil in the valve train area to worry about sucking it out.

Aside from environmental concerns, what is the advantage of a pcv system over a road draft tube?

Draft tube only works when the vehicle is moving to create the draw from the tube.

Right. But how often is a vehicle sitting still and running? For all practical purposes, does a pcv system really matter on a 74 year old truck? Will the advantages be noticeable? If it's only being driven a few thousand miles a year and/or gets it's oil changed every 3000 miles, will there be any real difference that should be considered?

Is there something terribly wrong with doing PCV the way it was engineered to work originally? On the subject of a PCV over a draft tube setup, maybe it was coincidental, but engine life almost tripled when the closed loop PCV concept came into general use, probably because virtually no road dirt was allowed to enter the crankcase. I was making a living running my own shop during thzat transition period.
Jerry

No baffles. The amount of oil collecting on the top end should not be a concern; no need to restrict with a baffle meant to keep oil from being vacuumed out of the valve train chamber through PCV valve to the intake manifold.

Advantage of PCV systems? Environmental concerns have been the compelling reason for automobile PCV systems for 60 years. Those who will remember the wide black stripes in the middle of highway lanes, caused by millions of cars belching blowby from road draft tubes. Air was unhealthy to breathe for humans and animals. California was the first state to mandate emission control systems in all vehicles sold in the state from the mid-1960s.

I’m not a greeny ( says a guy born and still living’ on the left coast) but….

If it Better for the engine AND better for the environment why would you not at least consider adding it, cheap and easy to install..
I’m up to the fire up and final (vacuum) test stage on the install on a 235 hi pressure….

Link to my install:
https://www.stovebolt.com/ubbthread...th-non-pcv-valve-covers.html#Post1538639

Chuck

CARB officials probably had to use a wheelbarrow to haul their Pinnochio noses around, as much as the lied about the environmental "statistics" they spouted back then. I did stay very busy retro-fitting vehicles to the state mandated "closed loop" PCV system mandated by California in the mid-1970s when I ran a shop in the San Joaquin valley however.
Jerry

Probably the best answer to your questions is for you to decide. In California, my 70 year old truck is now exempt from emission control compliance. The PCV system was left on the truck after exemption and the engine still runs well with no ill effects, perhaps extending the life of the engine too. The closed PCV system is doing its small part to protect the environment.

Engines with a PVC system tend to leak less oil since the crankcase is under negative pressure. I do use the term “tend” loosely!

CARB: California Air Resources Board

That looks like a Positive Valve Cover Ventilation system. I don't see how it ventilates the crank case. My stock PCV system sucks the gases out of the crankcase with fresh air entering via the valve cover. Plugging the road draft tube doesn't seem right.

Gord&Fran, Didn’t know a ‘54 3100 with 235 engine in Canada came with a stock PCV system. In USA, they did not. USA trucks were equipped with vented valve cover and/or vented oil filler cap and an open road draft tube. Not a closed system.

Warning: half-baked thoughts, theories, and opinions to follow…..

I think I understand what Gord & Fran is trying to say.

Having both the PCV suction point AND makeup air return point….in the valve cover, on an inline 6….makes a guy wonder how much ventilation the crank case is really getting.

In theory, it should still be placing the crankcase under a slight vacuum. But those two points being that close together, might also mean there’s more-than-ideal passing of fresh air straight from one to the other.

In a typical V8 arrangement, you are drawing from one valve cover, and adding clean air to the other. And the two are basically unconnected if not for the crankcase.

With the factory 261 PCV, the big alien looking (closed) draft tube apparatus is truly drawing from the crankcase. Probably somewhat better than the GM retrofit solution (which still seems better than an open road draft tube) being discussed here.

What happens when the motor sits runnning for an extended period without any draw?

Correct, and that is what is happening. Blowby has nowhere else to go (no draft tube, sealed valve cover) and is routed through top valve cover hose and PCV valve to the intake manifold then burned in the internal combustion process. Meanwhile, fresh air is introduced through the air cleaner and rear valve cover hose.

Can feel a definite vacuum pull when front hose is removed from valve cover while engine is running.

Nothing. The blowby gases just accumulate in the crankcase and are absorbed by the oil.

I guess worst case scenario is you need to change oil more often.

Which is one of the reasons that 3000 mile oil change intervals were the rule of thumb.

How often without having a filter?

I'd do it in 3000 miles or 6 months, whichever comes first

PCV was an option in 1954. You can see pictures of it in the factory assembly manual (RPO 217) and it's been talked about in this forum previously.