The Stovebolt Site Forums The Shop Area Engine Shop PCV in the Valve Cover???

I just finised reading all the threads on putting a PCV valve into my engine and am now more confused than before.

I've got a 1962 261 with a road draft tube and non-vented valve cover.

Originally I thought I'd put a PCV valve where the road draft tube used to be by either drilling filling the road draft tube hole with a 1 1/4" freeze plug having a hole in it for a grommet to seal up the PCV valve and then run a hose from it to the intake manifold.

I would PREFER to block that hole, drill a hole in the valve cover, weld in a baffle on the inside, put a grommet in the hole, put the PCV valve in that and run it to a hole I'll drill in an aircleaner and into which I'll put a grommet and a filter, like a more modern engine.

HOWEVER, I'm not sure that'll work, though in my 'shadetree mechanic's' imagination it should.

Dunno..havent tried it...but the pcv valve sucks quit abit of volume i think from the vacuum... so it might mess up the vacuum to the carb ya know..??? ya might hafta restrict it or something...dunno....someone will tell ya tho....

NM51,
Regarding your question and the questions
from the previous PVC threads, I don't understand why someone would want to complicate one of these old engines with a PCV valve. I am not anti-environmental, but the open system works fine and if smog certification isn't an issue, why re-plumb the thing. Am I missing something?

Stuart.

I installed one on my 54. What I have done is: Close the vents on the valve cover. Drill a hole in the cover for a PCV Valve gromment. I ran a hose from there to the wiper vaccumm port and used a tee fitting so the wipers still work (they have never worked well). Then I wanted to leave the draft tube cause it looks cool so I plugged the bottom of the tube with a freeze plug. Then installed a breather oil cap. The last thing is to adjust the carb. The motor needs fresh air to breath properly thats why the breather oil cap.
I have only driven 70 or so miles since this was completed but have not had any problems so far.
Steve

From what I have read it helps keep the engine cleaner.
Steve

There are a few purposes of the PCV filter and why to add one to these older engines.

First, it'll burn cleaner. Not only less air pollution, but more importantly to me, no oil out the bottom of the draft tube to burn on the exhuast, dirty up my garage or collect in the bottom of my bellhousing and get into my clutch assembly.

Secondly, using a PCV valve should make the engine a bit more fuel efficient. A nice thing when gas gets to $4/gallon or more. (PS thats been what it costs in lots of Europe, Mexico and central america for a long time only there it is US$1/litre).

Thirdly, it will make the engine a bit quieter and smother running.

Fourth, mechanincally, the valve itself is sort of a check valve- It allow vaccum to suck from the crank when the engine is producing vaccum, ie idling, and when the vaccum is low it closes to prevent blowing straight oil through the pcv valve into the intake, unless I'm mistaken.

In short, the advantages are asthetic cleanliness, reduced odor of burning oil, improved performance and gas milage. Some inline sixes of this era came with PCV valves, they just weren't the throw away kind and had to be cleaned periodically.

NM51,
Those reasons all sound very worthwhile to me. Maybe a PCV valve will be an addition to my old truck. I had my first 235 in 1963 and it was hot rodded to the gills...the neatest thing about it was the two giant Offenhauser aluminum breathers mounted to the valve cover. I see these on E-bay as "retro" or "rat-rod" items and the going price makes me wish I had stock in Offy!

Stuart.

In my opinion, the most important advantage to the PCV system is the reduction of oil leakage. Instead of putting pressure on the old seals and gaskets, it puts a little vacuum on them and that is a big reason since I really hate oil leaks!
Scott

you should put the valve on the crankcase, not the valve cover - have to make sure the engine can draw air from somewhere to compensate for the vacuum draw in the intake or you create a vacuum in the crankcase that'll cause problems - the early simple pcv setup used a vented cap on the valve cover, like on a 283, and the valve is sized for the engine, so careful which one you use

Bill

keep the draft tube. i tried putting the pcv in that hole in a cutout freeze plug just as you described on a 216. of course this engine was a little worn with some blowby & setup this way was too close to the crankcase & it sucked oil right out of it. i put the draft tube back in & cut off all but about an 1 & 1/2" or so of the downspout & welded the 1 & 1/4" freeze plug to it ( same diameter, perfect fit ). put the pcv valve in there & ran rubber vacum hose to the fitting on the manifold for the vacum wipers. i had a proffessional mechanic friend over at the time & after adjusting the timing & idle mix just slightly darned if it didn't seem to run even better than before! no excessive oil consumption & this did not affect the operation of the vacum wipers at all. btw, all this was done after welding up the vents in the valve cover. i've seen some 261s' from the early 60s' that were set up this way from the factory. matter of fact i just looked in my 1960 factory service manual & there's about a half a page covering it with a picture of the pcv valve.
robert

bluechev do you have the pcv part number you used?

Thanks

48 BigTrucks makes a good point I hadn't thought of, the vaccum in the crannkcase should help with the reducing pressure on the gaskets and keeping oil leaks down.

I should correct myself about the mechanical function of the PCV valve, it actually regulates the amount of vaccum applied to the engine. So, as many people have commented, it needs to be the right size for your engine. Basically if there is too much vaccum it closes. So, the direction of the flow through the PCV valve is important too.

I'm still a bit stuck on the idea of the PCV valve in the valve cover.

A friend yesterday suggested using a valve cover oil cap set up for a PCV valve, you know the ones that look like breathers but have a grommet and hose sticking out of them. He said the engine would breath through the carbs or the oil cap. If that is true then I can put a freeze plug in the draft tube hole. If it won't breath through the carbs then I could put one of those small K&N filters on the draft tube main body after cutting off the downspout.

Any thoughts?

When running an alum. Mercruiser cover (only having two holes, one to fill oil, the other for an atmospheric breather) and not having the ability to vent back into the carb thru the custom air cleaner cover. Should I simply run a PCV valve out of the rubber boot in the top of the valve cover and cap w/ a wire gauze dome cover?? or like we used to do and simply place a gauze wire cover on top and No PCV valve??
help me out guys.
I was just going to run an atmospheric cap breather in the cover and not the PVC, but does the PCV help w/ oiling issues if I don't run one ??? Ps this on a 292 motor.
I have a check ball breather vent on my old bikes for this very reason.

Okay... Talked to some more people and the idea with the PCV valve to circulate air through the motor using vaccum from the engine, and to recirculate unburnt fuel through the engine.

The PCV valve regulates the amount of vaccum used AND puts the air and gas from the crankcase back into the cylinders via the intake manifold.

The Road Draft Tube sucks the air out into the atmosphere.

With either system you need to get air INTO the crankcase. On the Inline Sixes there is either a 'breather' cap for the valve cover, no breather cap and vents in the cover, or something else along those lines.

An example of this set up is the V-8 350. One valve cover has the PCV valve connected to a vaccum source, either the intake manifold or the base of the carb. The OTHER valve cover has a breather element or another source of air, such as perhpas a line to the aircleaner for filtered air. Many of the more modern carbs have lines in the base of the carb for this reason and which often are capped 'cause they aren't being used.

On my 261 (and any other inline six with a road draft tube) you could put the PCV valve in either the valve cover or the original road-draft tube location for your 'outlet' line. The inlet will be a breather in the valve cover. Or perhaps visa versa, PCV from valve cover to manifold and breather filter in road draft tube location. Either way you gotta have an in and and out.

In the process of figuring this out I have learned a little about PCV filters, which are filters in the line between the crankcase and the intake manifold. These filters leave unburnt fuel in the air but take out things like carbon and suspended oil which, if not removed, contribute to the carbon and gunk build up in the cylinders/valves/etc...

Here is a link to a page I found in another thread with pictures and information:

http://www.condensator.com/

Here is another link, from another thread, with instructions on how to make your own!

http://www.himacresearch.com/books/hydro8.html

SO, what about having both in your valve cover, the breather and the pcv valve????

Well, my friends suggest that with the inlet and outlet in the valve cover you might not circulate air from the crankcase. So, I'm going with the PCV valve in one and the breather in the other. Since I'm going to use an inline 'pcv filter' set up, I'm putting the PCV valve in the draft tube location so I've got line to work with.

I was thinking this issue over and over too.

Got a 1959 235 with a 216 cover and wonna get a PCV because of the oil mess and milage reasons (price for a gallon of standard pump gas here in Germany $6,25 in the moment)

I saw factory modified draftubes that come with a PCV that goes to the aircleaner in a 1958 Chevy.

I think this is not a good idea for milage.

What do I want to suck from the crank case?
Answer: burned and unburned gases.

How do they come in there?
Answer: Blowby.

My first common sense solution:
1. Close the draft tube
2. taping in a nipple at the upper draft tube and T it via rubber hose to the wiper/manifold vacuum with a PCV valve.

Question: do I need a vented cover or must I close the vents to make sure it is not sucking to much air in to the intake?

The air from the blowby comes throu the carbs anyways, so do I need more fresh air comming in?

I just rebuilded a 1945 Willys Jeep engine that works exactly that way.

On the other hand, the vents in the cover relief the water boiled out of the oil. Will the steam get sucked down the pushrod holes or will it condense again?

An other issue is: The unburned gases I want for milage are lighter than air so they will cumulate in the upper valve cover right?

So my second solution is:
The draft tube makes a relative low vacuum and only at high speed. I don`t belive it is enoug to suck air down from the Valve cover.

So no whatever vent, I don`t need aditional fresh air. To get the gases I want, and get rid of the water, I need two hoses, one from the valve cover and one from the closed draft tube.

The Willys work that way, but it is a flathead and the valvecover is on the side with big enough oil backflow holes to suck the gases from the crank case to.

I also going to route one of these Condensator in the line

My thoughts so far.

Any ideas?

Frank

Stovebold, If you do a search here you should find a number of discussions on this topic. The '47-'54 Factory Assembly Manual has the CV RPO installation diagram, and our own Truckedup (Tony) has a quick and thrifty installation he designed. It is a good idea. Thanks for the Condensator link. Good luck. :p

Here's my newest plan:

I'm using a push in valve cover breather with an 5/8th outlet in place of the draft tube! This thing, which cost me about $8.00 came with a grommet and is exactly the right size to stick where the draft tube was. The reason I'm using it is 'cause it's got a baffle and filter in it to keep pure oil out of the pcv line that I'll run from there to the intake manifold (via a PCV filter).

I'm using a breather cap for the valve cover because my valve cover is sealed and the engine needs to breath through here to evacuate evaporated water and other suspended fluids when they aren't being sucked through to the PCV filter.

Please post where you found this gem.A part number would be great. The PVC valve need to come from a similiar sized engine.

The Push In valve cover cap is made by Mr. Gasket. I got it off a rack at NAPA. The side that sticks into the valve cover is 1" OD and with the Grommet (included) it is 1 1/4", the same as the draft tube opening.

I suspect this is a standard size for valve cover push in caps so the Mr. Gasket one isn't the only one you'll be able to find.

As far as the PCV valve itself goes, I havn't picked exactly which one I'm gonna use. What I'm planning on (unless someone suggests otherwise) is to put a tee in the offenhauser intake manifold and use a screw in PCV valve on one end of the tee. The other end of the tee will get run to a vaccum cannister that will also get vaccum from the dual acting fuel pump. Then I'll run a line from the vaccum canister to the brake booster, after running it through the appropriate filter to keep any errant suspended fuel/oil/crap from getting into my brake booster.

Here's a link to a picture of the push in valve cover breather cap in the draft tube's old home. (please let me know if you can't see it and I'll find another way to post it)

http://www.kodakgallery.com/PhotoView.jsp?&collid=870158533106&photoid=348258533106