Technical Flathead crankcase vent/PCV thoughts

I've searched in the past and I'll pursue specific PCV use when I get to the dual carb manifold in the future. Til then I have an easy idea to help provide a depression in the crankcase involving the air cleaner and the oil fill pipe. I'm fairly certain there's vacuum at the base of the average "tea pot" version air cleaner, so if a small tube were plumbed into the oil fill? I got the idea from some servicing to a Zephyr 12, there's a vent pipe from the valley to the air cleaner base.

Yes, the oil fill cap is vented and filtered, yes there will be vacuum all the time, more at speed, and perhaps can overcome the positive pressures through the fill pipe. I have a spare pump stand and fill, I'm probably gonna try it, just thought it might be a good thing to yak about. Crankcase depression, or vacuum, keeps an engine running cleaner and aids ring control so a worthy effort, yes? Whatcha think...

 

Usually you replace or modify the road draft tube to run a PCV valve that picks up the crank case air from there and run a breather on the filler neck to let air flow in and through.

This being a pretty generic PCV diagram it just shows air in, air flowing though picking up fumes and mosture and flowing out through the Pcv.

The problem with the pcv on the filler tube is you are picking up the air as it flows inthrough the breather cap and it never flows though the engine.

The mid 60's Corvettes that had the hose running from the car to the filler neck worked in reverse as far as I can figure with a tube running from the old road draft tube to the air cleaner to pick up clean air that flowed though the engine to the hose in the filler neck.

 

You have a good point there.
I'm in the process of adding a PCV system to my Chevy 261.
My first go to was this: http://devestechnet.com/Home/PCVInstall

But I think it's not a good idea.
1. The vapors cooked out from the oil tend to go upwards, so it makes more sense to suck them out at the highest point i.e. the valve cover, and not at the draft tube.
2. Removing the whole draft tube assembly and just bolting a PCV valve in the hole is asking for oil in the valve.
3. The control freak in me still doesn't like the idea of a (only somewhat, but actual pretty random) vacuum leak on my motor. And yeah I know, this is highly controversial, but that's how I roll.

What I gonna do is removing only the downdraft part of that assembly, but leave the oil filler tube part in place. I'm putting a filtered breather on top of it, so I got fresh air coming in to the crankshaft.

A baffled breather goes on top of my valve cover, and from there a hose into the air filter.
I think I make some sort of ventury at the end of that hose, to get more suction. An oil catcher can will prevent oil messing up my carb.

Frank

 

No road draft tube on a 59A I've ever seen. I've got 3 different ford flat motors and none of them have it. So where do the vapors go? Out the oil fill cap. The air cleaner is chambered. The fill cap is filtered, likely for pulsing at lower RPM and to help keep oil film from building up too much. Note the pipe in the base of the air cleaner in this Zephyr V-12 pic.

That opens into the valley. Oil separation is needed. There's a baffle going into the valley in the pump stand/oil fill pipe on the Ford flatty. I would think the vacuum at the air cleaner is highest at cruising speeds, crankcase vapors as well. The only way to get to them short of boring a hole in the intake to the tappet valley is there in the pump stand/oil fill. The filtered and vented oil cap will negate the action somewhat at low or idle speeds and the engine vacuum will have greater effect at higher speeds. It may be enough to aid oil sealing issues as well, that is unless I'm missing something. I have no dillusions that it creates a pure negative crankcase atmosphere but when and where it counts, at higher speeds? Maybe? Thoughts? "Why didn't Henry do it?" answers itself I hope.

 

I wonder what part 6757 is?

 

My 47 oil pan has a vent on the front corner that’s slotted on the back side. It is/was open to the crankcase. (Not now because I welded it up on the pan rail.)I’m going to run a pcv valve of some sort, just not there yet.

 

8BA. I'm running a 59A.

 

Off topic I know. But, what is the name of the color of paint that you sprayed on the pan?

 

It’s called Mayan Gold Metallic. It’s a single stage urethane. I got it from Summit but they quit carrying it. Kirker sells it though, and I’m pretty sure that’s where Summit was getting it. Sorry for the detour, Highlander.

 

'35-'48 flathead V8 crankcase ventilation. The outlet is on the lower R/F of the pan.

 

@ronzmtrwrx when it looks that good it's more like the scenic route than a detour. Very kool...

 

another view

 

I didn't consider the chamber on the rt front of the pan. I wonder how easily that could become a filtered inlet. I have some creative thinking ahead.

 

Why would you want to have inlet air from the dirtiest area of the engine compartment???

 

Well right now it's a wide open hole...in the "dirtiest area of the engine compartment" isn't it? Filter it or let it go to shit, gonna visit those thoughts.

 

Could you weld shut the outside slot for the original pan outlet, and add your PCV there? I would think that it is already baffled from oil and it would keep the stock direction and concept of crankcase ventilation. If you made up a hard line from valve to manifold, you could make it look at home. You also would close up the "dirty hole" at the bottom of your engine.

PCV valve

Blue is fresh air, teal is a filter, yellow is stock air path/oil vapor, red is it going down to exit, Pink is Valve, and green is hard line to manifold vacuum source.

 

Hahaa. Thanks man.

 

Why couldn’t you just drill the intake close to this area where the vapor starts down the pipe to exit and then install the pcv valve there, piped to the plenum under the carb? That’s of course if you weld up the open area on top of the pan rail over the top of the vent as I did to seal it off from the outside. Just have to make sure you will clear the generator where your pcv valve goes.

 

Hahaha!

 

No such provision on the 1½ flathead (zephyr V-12) oil pan. Explains why the pipe from the valley to the air cleaner is used? Would there be a detriment to reversing the path of case ventilation? Seal the oil cap? Filter the existing vent hole?

Have extensive parts drawings at the shop. Gonna check em tomorrow...

Quick edit: "WTF Jocko, why are you looking at this now? You're doing body work." Once the ass end is done it's time to cover up the engine compartment. So, do I visit and do this while I sit on the front tire or a milk crate or do it later bending may half crippled carcass over the fenders? Its wide open. Now or never I'm thinking, and shared thoughts are always good stuff. How I see it anyways...

 

Does the v-12 have a fuel pump stand/oil fill tube on it like the v-8 with this directly underneath it closing off the void between the bottom of the intake and the block? If so, then not having that vent in the pan is of no consequence. If the incoming air goes down through this tube and down into the lower block area, if you install a pcv valve in the front area of the intake, in my way of thinking, it should pull that air back up to it and into the plenum area. I plan to install a baffle of sorts on the bottom side of my intake to shield the pcv valve from pulling in oil spray. Of course, I could be way off base in my way of thinking. My wife thinks so lots of times.

 

Thanks....

 

Or even skip a step. Just drill a hole under the carb connecting the crankcase to the intake plenum, and plug it with a PCV valve. It sure would be compact, and also invisible from the outside. It's not a perfect venting route, but is an okay one and a heck of a lot better than no PCV.

But there must be something wrong with this super simple solution or everyone would do it.

 

The pcv valve would interrupt the massive airflow from the little two barrel.

 

The Zephyr has a fill tube twice as long, but I actually figure that's for easy oil fill. It doesn't have a baffle like a flatty. Open tube to the bottom of the air cleaner like.pictured above. When I get to the Offy 2 carb I'll add an actual PCV, but because I have an intact ready to go 1 carb gig on it a tube in the air cleaner makes sense. If the Zephyr has it...? If I tube up from the pan vent area I have to seal the existing opening. No big deal. Have a spare pan I can use to make a part, fab a bent tube, blah blah.

 

Dipstick?

 

Jims face about now.

 

I’ll be watching with interest. I’m sure you’ll come up with something that works.