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By cbass139 - 13 Years Ago
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What does the PCV valve really do? Seeing that the road draft tube is always pulling fumes out couldnt you just have a tube coming out the back of the valley pan that has vacuum hooked to it with baffling so it wont pull oil also? I ask because I got a valley pan with a PCV valve on the back with the original baffling but as you can see in the picture there is no "valve" in the middle but just a open tube. Thanks
Sebastian
Sorry no pic but the site keeps on saying i have exceeded my limit but I have never uploaded a pic and it is a phone pic so it is not a huge file so I dont get it.
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By oldcarmark - 13 Years Ago
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The Thunderbirds had the road draft tube down the back of the motor because of low road clearance.You can use that pan with a grommet and PCV valve plugged into the intake manifold as close to centre as possible or plugged into the carb if there is a provision for it like the 390 Holley does.The PCV allows crankcase fumes to be reburned instead of allowing unburned fuel and other fumes to escape to the atmosphere.The most noticeable improvement I found was that the garage does not smell of gas and oil with the PCV setup.That pan you have is hard to find.You might consider doing a PCV setup on yours.
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By cbass139 - 13 Years Ago
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Yeah, I got the pan with the PCV update in mind but like I said the "valve" is just a open tube on the rear of the valley pan. It has the original tubing from when it was used on the 60 truck already to go but with no guts inside it I wonder what the actual valve portion does seeing that the draft tube was always open, why do I need a valve that will open and shut when hooking it up to the plate under my carb?
Sebastian
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By cbass139 - 13 Years Ago
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If you want to see the picture I was able to post it on the FTE site with the same question. Here it is
http://www.ford-trucks.com/forums/1177787-pcv-issue.html
Sebastian
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By MoonShadow - 13 Years Ago
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The open tube just lets fumes pass through and out on their own. The PCV, positive crankcase ventilation, uses intake manifold vacum to pull the fumes out of the block and valley pan and send them through the engine. Its the positive part that makes them worth the effort. I had a mechanic show me a graphic demonstration on a Pinto 4cylinder car. It sounded good, idled fine, and drove without smoke. He pulled the PCV and blocked it and the car smoked BAD. Lots of blue oil smoke at idle. Quite impressive. Chuck
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By GREENBIRD56 - 13 Years Ago
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Cbass - The PCV for the application you are using had its valve screwed into the front of the intake manifold. It goes into a port that provided manifold source vacuum to P. brakes wipers - something - the port also incorporated a drilled hole into both manifold plenums. From the valve, a tube passed back to a baffled elbow on the valley cover. 
I have tried out the same valve (modified a bit) stuck right into the elbow at the valley cover - then plumbed to a carb port. It pulled way too much air due to the free flow and made my idle uncontrollable until I put an orfice in the line. As you can see in the picture - the orignal port was pretty restricted.
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By cbass139 - 13 Years Ago
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Thanks guys, I went and got a PCV for a 302 which is pretty close to my 292. All the info was very helpful. Will do the work this week and see how it turns out.
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By DANIEL TINDER - 13 Years Ago
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[quote]cbass139 (7/24/2012)
What does the PCV valve really do?
Aside from environmental concerns, it extends your oil life big-time. I believe the PCV spring also balances/limits crankcase vacuum and pressure.
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By 62galxe - 13 Years Ago
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I used the valley pan for PCV. I removed the hose adapter and threaded boss the screw goes into. Put a universal pcv grommet in the hole and used a pcv valve with a right angle fitting on it. hooked that to the back of my carb.
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By Ted - 13 Years Ago
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Here’s a partial list of discussions found on this site regarding PCV valves. Using the search function will bring up more. .
Blocking off the road draft tube Crankcase evacuation Finned valley pan and PCV valve installation Installation of PCV valve into the top of the block Installation of PCV valve at top and rear of block 2 Modifying valve covers for PCV valve installation Valley pan PCV valve installation Valve cover baffle for PCV valve Why a PCV valve or system?
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By cbass139 - 13 Years Ago
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Ted, I had done the search but did not see anything on what I was asking. I know I wanted to do a PCV and looked at what I needed and how to install it but I wanted to know a little more specifics of the actual valve and what I think I have found is that it creates the right amount of vacuum so as not to have a complete "leak" in the system. This tells me I can not run the gutless valve that came on the valley pan that I will be using. In all of the post you have there none has this information and thus my new post on a old subject. Thanks all
Sebastian
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By Ted - 13 Years Ago
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Sebastian. Your are correct in that a PCV valve is a controlled vacuum leak. It’s metered so that the excess pressure from the crankcase can be reentered into the engine and combusted without leaning out the engine. Most new universal carbs are calibrated to include the PCV valve air flow as part of the idle circuit fuel mixture which means not using the PCV valve on a carburetor designed to use one will typically have a rich idle and possibly to the point that the plugs have difficulty in staying clean at low rpms. Whereas a road draft tube only works when the vehicle is moving, the PCV valve works as long as manifold vacuum is present. If you’re looking for specific flowrates, here’s the link and information from a past discussion..
http://forums.y-blocksforever.com/Topic22760-3-1.aspx . The road draft tube concept was effective but not without problems of which the more significant would be emission deposits into the atmosphere as well as placing a large amount of oil on the roadways. The oil on the roadways was not only deemed a hazard for driving but a concern to the environment as enough oil was being deposited to make its way into the soil and waterways. The incorporation of the Positive Crankase Ventilation (PCV) system in the early Sixties provided a simple and effective solution to the aforementioned problems. Most PCV valves will move approximately 3 cfm of air during normal driving and up to 6 cfm of air under higher load conditions. PCV valves are tailored for specific engine combinations (usually by cubic inch) and as such, care must be taken when retrofitting these valves to engines not originally equipped with PCV systems in that the sizing of the PCV valve must be considered. A side benefit to the PCV valve system is that the crankcase is under a light negative pressure during cruising which in turn minimizes oil leaks that would be present otherwise. Utilizing a road draft tube in conjunction with a PCV valve negates many of the benefits of using a PCV system.
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By cbass139 - 13 Years Ago
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Thanks Ted, that is awesome info.
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By MoonShadow - 13 Years Ago
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Ted, When you dyno'd my new engine did you use my valley cover and the PCV valve thats in it? I bought that one on size to fit the hole and not by engine size. It could be too big and possibly be part of my erratic idle problems? Chuck
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By Ted - 13 Years Ago
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MoonShadow (7/27/2012)
Ted, When you dyno'd my new engine did you use my valley cover and the PCV valve thats in it? I bought that one on size to fit the hole and not by engine size. It could be too big and possibly be part of my erratic idle problems? ChuckChuck. While your aluminum valley cover had a threaded hole at the back of it for a screw in style of PCV valve, it has a plug in the hole. I did not find a PCV valve in your pile of parts. The flat bowl Holley carb you provided did have a hose on it though but no PCV valve sticking on its end. Your engine so far has been run without a PCV valve. That’s simply due to the engine being run with the roots blower and not the McCulloch unit. At this point, it’s been more expedient from a testing standpoint to not have PCV in place. When I get the engine back on the dyno, I’ll fit a PCV valve to it so it’s tuned with the valve in place.
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