I had asked about this a while back but just had not had a chance to get it do***ented like I said I would. It isn't the best piece of engineering in the world, but I figure it was an easy enough change to add and really wasn't much work. So my 292 was equipped with a draft tube. And the big ol' o-ring seal on mine was just shot out and instead of keeping the oil in and letting the pollutants out, it was just dripping all over the place. And since a PCV helps remove the **** that causes sludge I figured if I was gonna have to work on it, might as well use a better system. Here is what I bought to do the change. A PCV gasket from the HELP! section that you find in most of the major parts places - part no. 42052 It is a 1 1/8" mount hole A PCV valve - I used Fram part no. FV295. It would allow you to pull but not push air though. And of course some hose to fit these all together. So here is the draft tube as it came from the factory. Not elegant, but it worked for 50 years. Now off it went. You can see in the next two images where oil pools up before flowing back into the block and the mounting screws. Now there is a seal at that point to keep the oil from spilling out. Unfortunately my gasket was shot out and was just letting oil drip. Just two screws so it was actually pretty easy to do. Now off it went. And here is what the block looks like under there. I know, I really could use a steam bath for the engine. But it's a driver, not a looker. Now I just need a template for the opening. And the original gasket is a perfect solution for that. I used some of the same plate I had from making the fuel pump block off for this too. Plenty thick and it is free. And after a bit of cutting and grinding... And a few holes for the mounting screw and... Perfect! Now I didn't take any pictures of this, so I am going to have to jump ahead here. I pulled the valve cover off, drilled the hole with a hole saw and after good deburring, was able to put the new grommet in. Plumbed the hose to my air filter and was done. It took a few days because of laziness, but all in all it probably took no more than a couple of hours to accomplish. And now there are no more drips on the driveway. And no more puffing from the tube. I really didn't have an issue with too much pressure as it was, so as of yet, there has not been any negatives. Fingers crossed I won't find any either. Edit: Damn found a negative. Da Tinman showed me a diagram that just didn't jibe with what my best thinking was. So back to the drawing board. I had a spare 3/8 to 5/8 fitting that would fit into a plugged vacuum port on my manifold. So in it went and now I have the hose going to that for a vacuum source. Now hopefully I got it right.
Nice job. Simple & effective. Hopefully you have a source of "intake" air to complete the system. Normally the PCV would be plumbed to the intake manifold, and fresh air from the filter housing would be connected to the crankcase somewhere. Another option, for those guys who already have the intake off or plan to do so....remove the valley cover & drill/plumb it for the PCV...or find a late Y block valley cover which came that way from FoMoCo. Nothing wrong with the rocker cover, so long as you find the right location...the valley cover might look a bit less cluttered, or not, depending on one's point of view. Original Y design was the draft tube; then the draft tube was simplified & moved to the back of the valley cover; then finally the PCV was used.
I am ***uming that I will be ok for the intake because I have the open element style filler cap. So I figure that a vacuum is not really an issue in this case. And yes, I plumbed it to my air filter. I guess I thought it was sorta obvious so I didn't put a picture of it in the post.
The pcv valve should have manifold vaccuum to it. It needs a filtered vent on the other side. Plugging the pcv valve to the air filter isnt going to give enough vaccuum for the system to work properly. I like what you've done I think you just need to redo some plumbing.
I plumbed the PCV system on the Hemi in my Avitar the same way...into the base of the primary carb air cleaner/Stock oil fill cap. Instead of blocking off the draft tube, I used the draft tube hole in the rear of the valley pan to install the PCV valve. My reasoning was that of the draft tube/oil fill cap system kinda worked, then the added velocity of the air flowing past the fitting in the air cleaner would work. It works great...
Da Tinman, Thank you for the diagram. Once you showed the diagram, it all made sense. I have a port on the intake that will work out perfect for it. I will be revising the post here soon.
OK all. I fixed the source vacuum issue. And added the information to the original post. Now it is a mess in the engine compartment still, so I do know I have some re-routing and general cleanup to do. But the truck is still in shakedown status from an 11 year hibernation. So making things pretty are a bit low on my list of priorities. Thanks again guys.
Don't mean to hijack, but this is a good opportunity to run my idea past you guys. I was thinking of adding a pcv valve to my 235 chevy 6. I want the motor to remain as stock looking as possible though. What I was thinking of doing is block the end of the draft tube, and insert the valve right in the tube somewhere that is incon****uous. Problem then though is the air being ****ed into the slots on the valve cover wouldn't be filtered, but I could plug the vents in the cover and add a tube to the valve cover (possibly the back side where it wouldn't show) and run it to a filter. Has anyone tried this, and how well does it work?
roddinron, By no means do I have all the answers, but I have seen a few 90 degree elbows for PCV systems. Plus there seems to be some that look like with the correct hoses you can connect to each end and not be forced to drill for a grommet in the top of the valve cover. The ones I saw were for japanese cars, so you may have to look wide to find something suitable. Then you might be able to instead drill the rear of the valve cover and hide it by your firewall. Also, I have seen some where the oil filler cap held the PCV also, so that may be an option. When you want to look original, just pop it off and replace it with a correct one, and put the PCV one back on when you are ready to run. Basically mine is stashed in the back of the motor where the plug wires mostly hide it. And sooner or later I will be ditching the Open filter for something a tab bit nicer and wider and that should hide it even more. What I did was wander around Kragen looking for parts that could make it fit without having to hack motor up too badly.
Is there a "latest greatest" version of this story with a complete list of parts and a step-by-step set of detailed instructions? I was thinking about doing this to my 272. My road draft tube ***embly is leaking. Thanks.
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