Hot Rods pcv or draft tube??

what is the best way to go .draft tube or pcv . my mtr is 235 chev, I don't think any originaly had pvc , but I think ca made them retrofit some early cars . should it matter to the motor .one way or the other . I like the clean look of a draft tube .

 

*PCV

 

Without knowing what shape your car is in, if you had ever breathed the fumes coming from a draft tube at a traffic light you would opt for the PCV system. Even if your engine has no blow by fumes the PCV is superior in every way.

 

we all know what I meant , but what I wrote isn't at all what it was !!

 

PCV.. Why pollute???

 

Have a '54 Bel Air 2dr. sedan, replaced the vacuum wiper motor with an electric 12v unit from a '57 Chev. This left the 2 intake vacuum ports open, did a 2 hole tubing manifold and and hid the PVC behind the valve cover...
The '57 2 speed wiper was a direct bolt. dyno dave

 

I used a 261 out of a 59 Chevy with factory pcv in my fleetline
Perfect fit and solution

 

allways had a PCV in my sbc but only connected it up lately.using a 90 degree thru firewall fitting at the filter base.havnt smelt any fumes since.

 

PVC is for plumbing.

 

But you could use it for a draft tube

 

Always PCV


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PCV, on all my cars.
Road draft tubes stink!
KK

 

PCV.....actually a good (rare) government mandated upgrade.

 

The clean look of a road draft tube on the outside but it won't look that way inside.

 

PCV also does a better job of drawing moisture out of the crankcase.

 

It also pollutes the induction system.

 

I agree with the PCV option, BUT, this all depends if the Carb(s) are metered for the flow from the PCV system!!! I have seen many that are connected to anywhere there is vacuum and think its ''Golden'' when its not. So what ever the carb (s) are metered for will dictate the direction you should go. JW

 

PCV is by far light years ahead of a road draft tube . My old diesel has a slobber tube , it doesn’t stink so ad but it always drips .

 

Get a core plug (sometimes mistakenly called a freeze plug) that fits where the road draft tube did.

Drill a hole in the center of it, toss a PCV valve grommet, and a straight-up PCV valve in it. Plumb it straight up, and over and attach it to the manifold.

 

I switched to a pcv system on my 61 Ranch Wagon. An older gentlemen that bought a similar car new asked me about it and said, “I don’t blame you, that damn thing smoked and stunk on the way home from the dealer”

 

As told by engineers in 1961 PCV “ positively contaminating valves”. On my Y - Block ( yes it did stink) I put on a breather cap with a 1/2” hose fitting which I plumbed in to the air cleaner and left the crankcase breather open.... no more stink or oil dripping.

 

Did ya ask them why didn't they design it that way in the first place.

 

Actually closed crankcase systems were used years before the govt. requirement came into effect. Slow moving vehicles like a milk delivery truck or military stuff that might run in deep water did not use draft tubes.

 

I remember reading that Willys Corp reported longer ring life in their experiments with positive crankcase ventilation in the 1950s, years before it was required by law for emissions reasons.
I've added pcv systems myself on older engines.
Usually successful, but a few times I accidently ended up with over-venting and increased oil consumption, but most times it worked out fine.
I still use an old road tube system on my truck, and tell myself that one day I might experiment with adding a pcv, but I will wait until I'm ready to debug if something doesn't match the amount of venting that's apropriate. I don't want to put together a mismatch that over vents again

WHY BE ORDINARY ?

 

If attached to the manifold, how do do overcome the air leak you have now created.... only if the carb is metered for the PCV system will this work, then why not just connect to the carb fitting that is for this function. JW

 

What Chevy 235, that now has a road draft tube, also has a fitting on the carburetor for a PCV valve hose?

You don't overcome the tiny, metered additional air flow. If it proves to be an issue, you re-jet.

I have done 6-7 of these setups, on 216s and 235s. I have yet to detect an issue.

I didn't come up with this, or prove that it works.

Go see for yourself: https://www.google.com/search?q=235...54KHZ0JDKkQ_AUIEygC&biw=1536&bih=722&dpr=1.25

 

I would think that any fitting on a carburetor for PCV would not be metered, the valve is just connected to the throttle plate and sees manifold vacuum, the same as putting the PCV valve in the manifold. I never liked the idea of plugging the valve into an individual port as that feeds all vapors to one port all the time, but if tapped in right below the carb it should be fine.
An air leak? With manifold vacuum the engine is sucking fumes, with decreased vacuum the valve closes.

 

Yup, and go figure, this is where you tap a 235 manifold for the hose connection:

Right under the carburetor, servicing all ports.

 

I stand by what i wrote, and yes, what 235 carb ( is this an original carb or newer replacement ?)on an engine with a draft tube has provision for the extra air flow under the throttle butterfly. On a carb that is metered, and yes they are metered for this extra air flow, they are very different from each other. So you have done some with no issues, good for you, no really..... sounds as good as the thread on the PCV on a Y Block that was plumbed into a back intake runner and all that said that's what i did and i it works great....BS!! JW