It’s odd the PCV system caused an
oil leak. Somehow, it must have been too restrictive and the engine blow-by must have been too much for it.
Quote:
Originally Posted by blykins
That's why I don't use PCV valves on any engines. A breather in each valve cover is all that's needed.
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That's what I thought. That's what I tried and had issues. Here's my take on why I needed a PCV system. I used any old parts I could get and maybe I blundered into developing a working system due to luck.
A very long time ago, engines used a road draft tube that pointed down,, was angled back, and cut so that air passing under the car caused a slight vacuum to the crankcase and removed blow-by gasses and moisture. Running with only valve cover vents, and no draft tube or PCV would not cause a vacuum and contaminants would not be removed other than pushed out by blow-by.
When I first built my 428 I gathered parts from all over. A block here, and heads there, a crank from somebody else, etc. Although I bought a couple of complete engines none came with the carb plate for a PCV or any other PCV parts. At the time I thought a PCV was only for emissions and all I did was to install breathers on each valve cover and another at the back end of the intake manifold.
It wasn’t long before I discovered yellow glop dripping out these breathers and after removing a valve cover, all over the inside. As best I could determine, it was water mixed with detergents from the
oil. One mechanic said it was from using Quaker State
oil, but I switched oil and the same thing kept happening. So I decided to try a PCV system.
I happened to see a PCV valve with one barbed end and the other that would screw into my intake manifold. It was from a 1.5 litre 1990 Honda Civic. That was disconcerting as I couldn’t imagine a PCV valve from such a small engine working, but thought I’d try it.
I screwed it into the manifold and fed it from both valve cover caps as you can see below (the left one, not shown, is the same as the right one, shown):
The above picture was an experimental attempt and isn’t that cosmetically pleasing, but being lazy I havn’t changed it … yet.
How it works is shown below. I didn’t have and have never installed an oil filler tube, but it would make it easier to add oil, as of now I need to disconnect a hose at one of the oil breather caps so I can rotate the cap off.
Another idea would be to swap the rear breather with one that had a barbed fitting so it could suck fresh air from the filtered air cleaner. However, it does work and there’s no more “yellow glop”.
This all started out as an experiment, and worked so well I never bothered to change it. After roughly 5 years of cleaning up yellow goop from around the vents and under the valve covers, I installed this system and the goop was completely eliminated. It should be noted that I actually installed this system about 17 years ago and it's been working fine ever since.
For various reasons, I have checked my sparkplugs many times over those years and they all look good with no sign of running lean on those back two right hand cylinders, or any others for that matter. No doubt it’s because at high vacuum (such as idle and light cruising) the PCV valve closes slightly limiting the air fed back into the intake but opens up at low vacuum (high rpms under load) where the flow, though larger, is insignificant compared to the amount of air coming in through the carburetors.
So it appears to me that even a mismatched PCV valve can do the job when one considers the length of time I've had this installed without any problems.
Of course I could be all wrong and that I’m getting away with it as I don’t race my car or otherwise let it scream for extended periods.
7Likes
PCV valve and relationship with rear main seal
Linear Mode
