ByByeAmericanPie

1961 - 283/245 - 2 WCFB Carbs

Problem: PO plugged the draft tube opening in behind the manifold. There is a vented oil cap on the filler tube. Car is using oil (just rebuilt 7000 miles ago) and oil pressure reads high (60+ psi at the gage)

Questions:

1.Could the absence of this tube or a PCV be causing the bulk of my oil consumption?
2. If I install the OEM draft tube system will this provide sufficient ventilation to the crankcase?
3. If I decide to go to a PCV setup: Would it be ok to put a PCV valve into the draft tube opening and pipe it to the unused vacuum port on the carb without risking sucking too much oil into the intake? Would the vented filler cap be enough intake without venting the valve covers?

Thanks in advance!

66jack

First off, Is the 'tomato can' still under the intake?

ByByeAmericanPie

Unknown. When I open up the draft tube hole I will check with my finger to see. If not, I have a new can that I can install.

SDVette

Wait for some of the real experts to chime in... but I've recently been on a PCV hunt as well. My motor uses WCFB vac, through a PCV valve, to a hole drilled in the rear of the manifold, with a home-made mini-can (drilled tubing) inside.

To try to answer your questions:

1) I've been assuming that with a vented oil cap, you can't build up enough crankcase pressure to do any harm.. The downside is that oil vapor will be pushed out the vent, and cover the motor over time. Experts to confirm.

2) You'd be stock then, right? Environmental concerns aside, I would expect this to work OK, but you are venting to the air.

3) I think you would then have a system similar to mine (my block is a 1970 - so no draft tube).

wmf62

road draft tube is not as efficient as a pcv, and can be 'messy' because the vapors are 'exhausted' under the car, a pcv draws the vapors into the engine and combusts them. given the choice, I would always choose a pvc system...

the ideal way is not use the old road draft tube hole, instead draw filtered air in through one valve cover and suck it out through a pvc in the other valve cover.
Bill

Frankie the Fink

Answers:

1. It could be causing some of it -- blowby (even on a freshly rebuilt engine) past the pistons pressurizes the crankcase, and, with no other outlet it may push oil/vapor out the vented filler cap....but that would be VERY noticeable I would think.

2. The draft tube ventilated crankcases was used in 1,000s of cars well into 1961 for Corvettes - it'll be sufficient but not optimal. It is a 'passive' system depending on scavenging to pull out vapors, NOT a vacuum driven system like a PCV valve.

3. Yes, and, yes. What you are describing is the RPO-242 optional California 'open' PCV system first used on Corvettes in 1961 - it works. If your engine was rebuilt to stock specs you should not experience engine oil 'pullover' into the intake.

FTF

ByByeAmericanPie

Thanks Frank. One more question, if I use the stock draft tube port for a PCV and pipe it into the unused vacuum port on the carb, do I still leave the tomato can in place?

wmf62

yes, the 'tomato Can' is a rudimentary oil separator to strip liquids from the vapors.
Bill

ByByeAmericanPie

Any suggestions on which PCV to use that fits the original draft tube hole?

ByByeAmericanPie

This is kind of like the setup I was thinking about...if I could only find a PCV Valve like this one...

Frankie the Fink

YES !!! That tomato can is actually a vapor canister; its job is to separate the oil from the vapors to avoid the very issue you mentioned above, to wit, NOT sucking liquid oil into the intake ! The original setup had an adapter on the draft tube hole that was connected to the PCV valve located AT THE REAR OF THE CARB via a rubber hose.

There was actually a kit sold that converted a car to the PCV system.
You'll want to emulate that as closely as you can...you will also want to get a '63 RH side spark plug loom (shown in the kit) to secure the wires since your road draft tube (which formerly did that job) is gone now

A CV-590 or equivalent PCV valve should work nicely; Corvette vendors make repros

Frankie the Fink

Just saw your picture -- that will work; however the original CV-590 PCV valve has one end that is screw in (see the picture); so it may take some trial and error to find one equivalent with hose fittings on each end.

It would be easier just to use the bronze adapters shown in the kit above to mount the original screw-in PCV valve IMO. Corvette vendors sell the adapters too.

ByByeAmericanPie

Does that kit have a part number that I could search for? And, if I have to use the threaded pcv I guess I could still hose over the threaded portion and be ok...

narlee

You probably don't have enough hood clearance with that spacer.

ByByeAmericanPie

Huh?

ByByeAmericanPie

Frank, This is the part that I am having a hard time locating...

wib1961

That part is very hard to find BUT does come up on ebay at times. Keep your search going for about a month and one may pop up. Try to get one with the bolt that should come with it, but if not you can get the bolt from any hardware store or use the one that came on the road draft tube. Get your big checkbook out.

Frankie the Fink

Here is the Paragon item -- they are usually out of stock, call to check:

https://www.paragoncorvette.com/p-34...vent-tube.aspx

However the rubber grommet and pipe system works equally well and saves you money:

http://www.ebay.com/itm/1955-68-Chevy-Small-Block-or-58-65-348-409-Big-Block-PCV-Valve-Conversion-Kit-/321126271779?hash=item4ac49e0b23&vxp=mtr

wmf62

Frank's recommendation above will work very well, and will save you beaucoup $$.
Bill

MikeM

If you don't mind slogging through the junk yards, that part was installed on millions of '63-'67 Chevys. Or try an engine core scrapper.
Or one of the car guys down the street?


I have two or three of them. I'd like to give you one but I see today's ridiculous prices on them, I'll just hang on to mine and wait for the next price bump.