[boybowser]

1957 Chevy with original 283, treadle vac power brakes and push button coordinator, I want to remove the road draft tube and install a PCV system, I am concerned that pulling any more vacuum off at the carb is going to cause some issues, should I be concerned and if so any suggestions as to where else I can pull vacuum, this is all original I saw something about a carb stud with a through hole that may work but again I may be starting to pull a lot of vacuum on the engine and I wonder if that could be to much. Thoughts

 

[ehrawn]

What a coincidence. I’ve been doing a bunch of reading today about how to switch from the road draft tube to a PCV system. To answer your question, I don’t think you’ll have to worry. This article claims measurements of 6 psi positive in operation and the PCV system should be designed to lower to about negative 1-3 psi: a difference of 9ish psi at max operation.
Quick Tech : Benefits of Lowering Crankcase Pressure | Part 1 - DSPORT Magazine

Which valve were you planning to use? Maybe I can find what psi it’s designed to. We’re you going to ventilate from the road draft tube opening?

 

[Rick_L]

I am concerned that pulling any more vacuum off at the carb is going to cause some issues, should I be concerned and if so any suggestions as to where else I can pull vacuum,

You should not be concerned.

What you need is a fitting that goes in the block where the road draft tube went. Mid 60s cars had them. Run a hose from that fitting to an inline pcv valve and another hose to a vacuum source at the back of the carb. The 283 that came in my 67 Nova had such a setup from the factory. It's simple and works great.

 

[Pops @ Tri-5.com]

Eckler's has a kit here: Chevy PCV Valve Kit, Small Block, With Metal Elbow, 1955-1957

 

[ehrawn]

What you need is a fitting that goes in the block where the road draft tube went. Mid 60s cars had them. Run a hose from that fitting to an inline pcv valve and another hose to a vacuum source at the back of the carb. The 283 that came in my 67 Nova had such a setup from the factory. It's simple and works great.

There's one additional component that I have to contend with. I don't think i installed a ventilator in the valleys for my 327. Hopefully, you did.

 

[Rick_L]

That baffle is needed whether you have a road draft tube or a pcv valve.

It may not clear an aftermarket manifold, but some clearancing with a BFH will fix that.

 

[ehrawn]

That baffle is needed whether you have a road draft tube or a pcv valve.

I was young and dumb. Doing my best to makeup for past mistakes.

 

[Rick_L]

You weren't the first one to leave it out.

 

[angs1957]

Just querious you have an all original engine set up, why do you want to go away from factory fittings (road draft tube)

 

[boybowser]

Just querious you have an all original engine set up, why do you want to go away from factory fittings (road draft tube)

This car is meant to be a daily driver, past experience is that overtime the draft tube makes a mess on the garage and if it does not detract from performance it helps keep gasses from venting to the outside world, not a cure all but it helps. Also replaced the points with a pertonix ignitor got tired of messing with points. Did a few other things like added self adjusters to brakes so I guess to say it is all original is a bit of a mis-stament, should have said it is the original manifold and does not have any pick off except at the carb base. If it proves to be to much trouble I will just leave the draft tube on it. Hope the explanation helps

 

[Beachcomber]

I converted mine many years ago, used the Ecklers kit and it worked fine. Both valve covers have breathers, and all seems good. Had to adjust the carb mixture screws to compensate for the vacuum change. Not sure if I have that oil Seperator as I did not build the engine. Given the type of fair weather use we generally give our cars not sure if the water/oil separator is absolutely necessary. I did recently find this adapter part that appears a bit better than the rubber grommet set up. But cannot remember where I got it. Its just the part that attaches to the back of the block. One of these days when I need something to do, was thinking of changing it out. Rubber may get brittle and crack over time. Just a thought.

 

[KENTON]

I got this PCV from summit racing. I had to put some vaseline on the grommet to get it to go in, but it did. then I had to file the top of the transmission so a bolt would go in all the way. I made a bracket to hold the PCV in incase of pressure from the crankcase it wouldn't pop out. https://www.summitracing.com/parts/sum-440308

 

[KENTON]

Sorry my pictures doubled up.

 

[boybowser]

Sorry my pictures doubled up.

Quick question where did you pull the vacuum for the valve

 

[boybowser]

A follow up question re the oil fill tube breather cap, can it be cleaned if so what is best practice and how often should it be cleaned?

 

[Farm Boy]

My '56 had an aftermarket PCV setup installed by a previous owner. They installed a Tee fitting between the carb and the power brake fitting. Both the PCV and the power brakes worked great.

 

[KENTON]

Quick question where did you pull the vacuum for the valve

There will be a 3/8 hose that goes to the rear base of my carburetor.

 

[ehrawn]

I did recently find this adapter part that appears a bit better than the rubber grommet set up. But cannot remember where I got it.

Widely available. It's one I was looking at: 153781 - 1955-67 Chevrolet; Crankcase Vent Tube Assembly; Small Block

I got this PCV from summit racing.

$17! can't beat the price here.

 

[mr55/56]

On my 63 327 I was very upset when I had to run a tree hugging PCV valve to clear the 700R4 dipstick. I really wanted a cool road draft tube.

 

[ehrawn]

On my 63 327 I was very upset when I had to run a tree hugging PCV valve to clear the 700R4 dipstick. I really wanted a cool road draft tube.

This is how I ended up where I am. I immediately labeled not relevant to performance and didn’t include it in my build. I was too dumb to actually learn how valuable it was for power and oil life. Now that I know better, I’m building a functional crankcase ventilation system.