The Stovebolt Site Forums The Shop Area Engine Shop 235 & PCV valve

I would like to cap off the current breather tube and install a pcv valve in the tube. In addistion, i would also like to use a solid cap on the valve cover rather than a breather cap. Does anyone have any experience with this type of set up and know if this is sufficient ventilation for the motor. It looks like later model motors have a similar set up shown on pg 28 in the 1947-1954 factory assembly manual

here are some pics of my set up and the pic out the assembly manual

http://i864.photobucket.com/albums/ab204/millermd/motor1.png
http://i864.photobucket.com/albums/ab204/millermd/motor2.png
http://i864.photobucket.com/albums/ab204/millermd/motor3.png
http://i864.photobucket.com/albums/ab204/millermd/235manual.png

The PCV is the exit.
Where is the entrance?

in picture #1 you'll see the original down draft tube. I cut off the part that goes down past the pan and welded a cap on it. I then cut a hole in the cap, intalled a rubber grommet and a pcv valve....from there, i ran a vaccum hose up to the firewall into a Jegs oil/air separator (picture #2)and out into in another foot or so of vacuum hose and into the intake manifold where you pull vaccum off for various items i no longer use. Picture #3 shows the cap on the valve cover instead of a breather cap and picture #4 shows a similar set up from the assembly manual. Any pressure in the pan is getting sucked by vacuum throught he PCV valve and back into the manifold.

Where are you putting the air INTO the engine? There must be an inlet point, either through a filtered vent in the oil filler cap, or a tube running from the clean side of the air filter to the valve cover. Just sucking on the crankcase is not "crankcase ventilation"
Jerry

hotrod lincoln,

Looks like I will need to run a breather cap. I just like the look of not having a big bulky cap on that nice looking polished offy valve cover. I guess the only other option would be to drill a hole on the backside of the valve cover, tap it and place a fitting into it an run a line to the carb like you mentioned. I did run the motor without a breather cap for a while....what damage could that do?

You're still not getting it.

Here's a good looking breather for your valve cover.
I used one on my Offy.

http://cgi.ebay.com/ebaymotors/EDEL...torsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

The whole idea of PCV is to introduce clean air into the engine, not dust-contaminated outside air, then pull the crankcase vapors into the intake and burn them rather than allowing them to escape into the atmosphere from a road draft tube. The tree-huggers in California started the practice about 50 years ago, but to everybody's surprise, engine life improved dramatically because dust was not getting pulled into the engine with the ventilation air. I was at a seminar for yacht owners several years ago sponsored by Detroit Diesel when the question was asked "How long will a Detroit engine last before it needs an overhaul?" The answer was simple- - - -"Long enough for it to eat 10 pounds of dirt!" The cleaner an engine runs, the less wear happens. If you pull the crankcase ventilation air from the air filter after it passes through the filter element, that's the best source. Next best is a filtered oil filler cap, a breather such as the one in the link with a foam packing inside, or some other way to strain the dust out before the air goes into the crankcase.

Does that explain the situation better than a bunch of smart-donkey remarks designed to ridicule your understanding of how the vent system works?
Jerry

I see your manners are as bad as ever.

Mike - the similarity ended when you used the factory arrangement minus the oil fill/ breather on that earlier crankcase ventilation setup - it's not just a 'plugged off' road draft, it also supplies the outside air .... my 46 GMC had that factory setup with no fill hole in the valve cover

Bill

I have a 248 GMC in a parts truck. In place of the road draft tube it has the cutest little oil bath air cleaner to filter the incoming crankcase air. The PCV valve draws from the valve cover.

I am thinking about grafting this setup onto my 261.

Carl, how 'bout a pic? Thanks!

I have that same setup with the 235 I picked up recently.

https://picasaweb.google.com/wmhatfield/New235#5613808806278422594

https://picasaweb.google.com/wmhatfield/New235#5613808824476673266

https://picasaweb.google.com/wmhatfield/New235#5613808835204668226

Thanks! Think I'll keep an eye out for one.

BigTonka, that isn't the GMC setup. Yours is Chevy. It will work just as good though.

By '59 GMCs used one with a paper element. I have one on my burb.

http://i232.photobucket.com/albums/ee12/cletis_photos/1954%20GMC%20Suburban/pcv1.jpg

http://i232.photobucket.com/albums/ee12/cletis_photos/1954%20GMC%20Suburban/pcv2.jpg

"Vintage Truck" magazine ran an article on the stovebolt PCV system a few months ago. Lots of pictures and info.

I though a Chevy was the destination vehicle? Both Husker and CH3NO2 have Chev's?

mine is a chev

I thought Racecarl said he had one from a 248 and you said you have the same set-up. I pointed out that you don't have a GMC set-up. However, either set-up will work on either make of engine.

Is there any preformance value to a pcv system? i saw one years ago on a plymouth flat head 6 and the guy said it improved preformance. ??

Hmmmm- - - - -is that guy available to talk to my garden? It's about time for another application of fertilizer! PCV is just a way of dealing with vapors in the crankcase without venting them to the outside atmosphere. A crankcase is going to have a certain amount of combustion gas blowby, oil vapors, and other contaminants anytime the engine is running, so it's got to be vented or pressure will build up and blow oil out past all the gaskets and seals. One way to handle the problem is to create a positive flow of air through the crankcase and into the intake manifold with a pulsating valve that prevents too much vacuum loss. That's all the PCV valve does- - - -it just takes little gulps of air out of the crankcase as the manifold vacuum fluctuates. It doesn't help or hinder performance.
Jerry

Thanks. I didn,t know if it would help or not. I would like my truck to be close to orig. but still run better. If I see something that looks interesting I ask and get as many opinions as I can.

The big horsepower drag race car motors have a sizable hose from each valve cover to the header collector. I think the term is "scavenge"? I think the purpose of this is more than just capture the stuff instead of venting it to the atmosphere.I think the fellow with with the Plymouth has his wires crossed. Don

Don, since 1/4 mile needs to have four turns in it before it becomes a race track, I'm not terribly familiar with drag cars. I believe the vent to the headers is more to eliminate explosive vapors by burning them than for any power boost. Any alcohol/nitromethane mix that gets past the piston rings, combined with lubricating oil turns into a compound chemically similar to nitroglycerine in a very short time. That's why we used to change oil between runs on the alcohol-powered drag cars a few years ago. Now, they change engines after one pass. Producing thousands of horsepower for a few seconds tends to make top fueler engines about as reuseable as toilet paper!
Jerry

What is exhaust scavenging?(vacuum behind exhaust pulses)
Exhaust scavenging is the ability of the exhaust to create high velocity situtation where while overlap is ocurring the combustion chamber can be completely emptied and actually filled with fresh air from the intake. This can only happen while the piston is at or near TDC and the intake and exhaust valves are open.

I googled it and above is one of the hits I got.

Don

Don, I ran high horsepower door slammer cars for a few decades with the system you described. It works like, and does exactly what the down draft tube on our truck engines does. It uses a type of Venturi effect to draw out crankcase vapor/pressure. In the case of our trucks road speed creates the pressure differential for it to work and in race cars it is the speed of the exhaust gas doing it.

In the race cars you have an oil separator/breather up on the valve cover that functions like the the one in the down draft tube. The race system used one way valves down on the header with a small angled pipe welded into the collector. It is angle cut on the ends just like our breather tubes for the same reasons. Race cars, at least those without zoomie headers, need to be in great mechanical shape for obvious reasons. They just want pretty clean air coming out this system. Last thing you want is any oil mist coming out the exhaust and hitting the slicks.

Chuck

Bigtonka, I know many years have passed, but if you are still around would you repost your pictures of the 235 PVC install from 07/17/2011? Google says it cannot find the pictures today. Thanks

Bigtonka has not even logged in for 4 1/2 years. Chances are slim to none that he will see this. Sorry