The Stovebolt Site Forums The Shop Area Engine Shop '36 Chevy PCV

Has anyone put PCV on a 207 cubic inch Chevy engine? If so, can you share the details? And please self proclaimed "expert" non-1936 Chevy owner spare me the commentary about what a bad idea this is.

I would like to do this in a "stealth" way that it is there and working effectively but is not a blatant, in-your-face deviation from original.

Thanks!

It’s not 207 but good info that will apply..........

http://devestechnet.com/Home/PCVInstall

Showkey,

Thank you so much for that link. It definitely provides some valuable information for starting the project. The 207 engine is a little more challenging though. The 207 valve cover does not have an opening through which oil can be poured. Oil goes in through the same hole in the left side of the block that the draft tube is in. So the draft tube hole cannot be plugged with a freeze plug into which the pcv valve is installed.

Where there is a will there is always a way, but it would be really nice to know if someone has already done this modification successfully.

Ray, later GMC big trucks had a PCV setup with your configuration, partially shown here. [my 46 had it] couldn't find a pic of the filler tube side, but instead of plugging the draft tube hole, an air cleaner was used on it .... maybe some GMC owner can supply more info

Bill

Here is a picture of a factory truck PCV set-up.

"Ray, later GMC big trucks had a PCV setup with your configuration, partially shown here."

Flxible,

Thank you so much. That is really food for thought. Apparently in this version the suction is applied to the valve cover. Is that correct? If that vacuum routing were used, an air filter could be attached to the draft tube to keep dirty air from entering the crankcase. What do you think?

"Here are a couple pictures of 235's I did."

Dave,

The pictures of the oil fill tube at the side of the block modified for a pcv valve are also really valuable food for thought. I can't cap that tube on my '36 engine as it is the only way to put in engine oil.


Fixible and Dave, since you have both done this conversion successfully do you know if it matters whether the air flow through the crankcase that admits air through the valve cover and removes it through the crankcase or vise versa?

I think my approach here will be to find another draft tube and valve cover to modify so I can keep intact originals. That what I did on the 3.55 rear axle conversion (kept the original '36 rear axle) that I did following your suggestion Dave. Thank you again for that. It is really working out nicely.

I see no reason the PCV valve couldn't be in the valve cover, that is the way most later engines are set-up.
Just be sure that the air intake for the crankcase is filtered.

Yar...........on my GMC 228 the draft tube is the oil fill tube as well.
I used the stock draft tube, modified it, by cutting it in half, turned the top welded it back together, use the draft inlet as the PCV valve location. Installed a valve cover with vent.


Send me a PM with your email will pics.

I have a 49-3100 with vacuum assist disc brakes. Can I also tee in the manifold and install a PCV valve? Thanks advice.

I run disc brake booster off the vacuum wiper port and the PCV to the main vacuum port.

Thanks for reply. Just so I am clear (please bear with me). I have electric wipers. I only have one port on my manifold which is now used for my disc brake booster. So can I tee off my one port and use it for both my disc brake booster and PVC? Thanks for your help.

Yes but there exceptions. All PCV's aren't the same. Some flow alot more than others. A PCV that flows too much will rob vacuum needed for your brake booster. I run a PCV on a 49 216 and it's tapped onto the same port/line as the vacuum wipers are connected. I had quite a few differing PCV's in my stash and found one that worked. It is a Purolator PV141 PCV valve. One of the PCV's fowed so much the wipers didn't even attempt to move.
Deve's tech-net site has a great writeup on adding a PCV.
http://devestechnet.com/Home/Index

Thanks for response and clarification

Understand that a pcv is a controlled vacuum leak. Some more than others. I think a great setup would be one that included an oil separator, so you don't wet down the intake manifold with oily vapors. Picking the wrong valve can reduce the vacuum signal to the carb and create a whole host of A/F problems. IMHO

"Re: '36 Chevy PCV [Re: yar] #125760106/03/18 05:36 AM
P
Pre '68 Dave Offline
Shop Shark Joined: Jan 2001
Posts: 4,884
Snohomish,WA,USA
Here are a couple pictures of 235's I did."

Dave,

Thank you so much for that information. I duplicated your efforts although my project is a 1936 Chevy 207 engine. After installing the PCV valve to a modified draft/oil fill tube and connecting the PCV valve to manifold vacuum using the 1/8" female pipe threads in the manifold for the windshield wiper vacuum source I discovered that no vacuum was developed i the crankcase. To find the vacuum leak I applied about 5 psi pressure from my air compressor into the oil dip stick hole in the block and traced the sound of leaking air to the back of the engine, between the engine and flywheel. Because the engine is in the '36 pickup there is no direct view of that area so spraying a soapy liquid in there would make bubbles but their exact location would not be visible.

Because Chevy did not use a rear main seal until about 1940 the massive air leak is probably along the crankshaft - rear main bearing interface. Have you encountered that problem in the PCV conversions you've done on early Chevy engines?

It looks like the next step will be dropping the pan and hoping that when Egge Machine redid the main bearings they used shims under the caps to allow adjustment of the bearing clearances.

What do you think?

Thanks so much for your input.

"Yar...........on my GMC 228 the draft tube is the oil fill tube as well.
I used the stock draft tube, modified it, by cutting it in half, turned the top welded it back together, use the draft inlet as the PCV valve location. Installed a valve cover with vent.


Send me a PM with your email will pics."

Showkey,

Thank you for that kind offer. I sent you a PM.

It looks like this may not be possible. Pre 68 Dave just called my attention to the slinger behind the rear bearing journal. It looks like the slinger is centered in a groove machined in the block and main cap and it looks like a drain back hole directs oil from the slinger back to the pan.

In that case what I'm attempting can't be done because the drain back hole provides a route around the bearing for air to leak through and that is what makes it impossible to create vacuum in the crankcase.. Can anyone who's been following this discussion think of a solution to that problem short of pulling the engine and machining the block and main cap for a seal? At age 73 that's not a can of worms I really want to open.

Some people have mentioned a check ball in that drain back hole. Does anyone know if that check ball is present in a '36? If it is there crankcase vacuum would tend to pull it open keeping the air leak constant.

To all who have commented on this, thanks for your interest and if you have any ideas on how to move forward I'd really like to hear them.

It seems to me that vacuum would indeed tend to keep the ball unseated while the engine was running.

Not sure if my situation applies here, but my other toy is an air cooled VW that I installed a PCV system on. It also has a slinger instead of a crank seal. My logic was that there just would not be much air coming in through that drain back hole so I did not worry about it. I installed a vent with filtered air to the crankcase and a PCV valve on the oil filler cap. The filtered vent is 3/8 tube so is a lot bigger than the drain back hole. I sealed off the draft tube and it seems to work OK. I monitor pressure/vacuum in the crankcase and check for oil coming out past the slinger, no problems either way.

I did this modification to eliminate the regular drips that came from the draft tube and of course that has been eliminated. Some adjustment of idle mixture and rpm was needed, but no other changes. The point is, sometimes I can overthink things instead of just doing the project and seeing if it works.

"My logic was that there just would not be much air coming in through that drain back hole so I did not worry about it."

59 fleet,

On my ;36 the oil drain back hole passes so much air that neither manifold vacuum from the running engine nor my air conditioning service vacuum pump pulls enough vacuum in the crankcase to move my vacuum gauge needle at all. For comparison purposes I sucked on the vacuum gauge and that registered 10" of vacuum.

I think I should accept reality and conclude that because sealing the entire bell housing area with its many openings is not practical the PCV concept is not practical without a conversion to install a rear main seal.

Thanks again to everyone who commented on this project.