So, I built a SBC and am running "Chevrolet Script" valve covers in my 39 Ford Tudor. These of course do not have a PCV opening. The intake I am using is an old Weiand, without a breather. I drilled a hole in the back of the intake for the PCV valve and put an oil shield on it. I got to thinking about it more and remembered that later SBCs had a breather (routed to air cleaner), on one VC and the PCV on the other. It got me concerned if I had it properly vented, and I was wondering what others have done to solve this problem? Thanks in advance TR Steve
An old intake should have the hole in the front for the oil fill tube or the boss you could drill for the tube. For many years sbc's took air in through the fill tube breather and out of the valley through the back of the block via the road draft tube and later by pcv valve. Should still work if your oil baffle is good.
If you have a newer style block, post 67 ,, i believe,, you wont have the road draft hole next to the distributor hole, but earlier blocks have them,, all the small journal motors, 265,283 and 327 search for 'road draft tube' lots of info here about that,, here is one: http://www.jalopyjournal.com/forum/showthread.php?t=92105
Yes post pic. As said before maybe able to bore boss with 1 1/4" hole. The PCV set up you did I did as well and the fresh air comes via the filler tube with a breather cap. Now as far as valve cover, since all you need to do is have fresh air in. You can come from the side wall with an elbow of some sort. If it was mine I wouldn't do the valve cover thing.
What are folks doing for a oil shield under a pcv valve that is tapped into a sbc intake behind the carb in front of the distributor? I want to do this so I can use my vette v/c on my 350 with an old school oil fill tube with a breather cap on the front of the intake, but am stumped on what to do under the intake manifold....thanks
There must be 6 or 7 complete threads on this subject concerning finned VCs from the 50s. A search using PCV valve and possibly Cal Custom should bring up a lot of ideas to accomplish this. This gets asked every other month.
I understand how it was done on early and late SBCs, I thought I would check and see if someone had come up with something "out of the box". I did a search, maybe you could help me out with a link? Not interested in drilling the tube in the front.
You have to search: crankcase ventilation ....and a tech article! http://www.jalopyjournal.com/forum/showthread.php?t=64338&highlight=crankcase+vent
The "tech" article thread is how I fabricated it. Of course, however, I drilled the hole in the area of the intake that covers the lifter valley, not the runner. With a oil shield drilled (and tapped 10/32 bolts) on the "underside" of the intake, respectively. But I need to get fresh air for it to be truly "vented" (and please, let's stop getting trivial, I know what PCV is). I'm thinkin' now to drill and tap the front of the intake for a 1/4 pipe thread (not some overkill 1 1/2 " hole ) for a fitting similar to a rear-end vent. I want it functional and well thought out. Just not big and clunky. Thanks for the links
Smog systems, positive crankcase ventilators (PCV's) is possibly one of the most misunderstood subjects there is. Hopefully, to try and simplify things: in order for the PCV system to work you need three things; Fresh air intake, a port into the inner areas of the engine and a vacuum hose with a PCV valve incorporated into the hose from the crankcase/inner portion of the engine. If you are working with an engine that has no access into the block like the early 265's 283's and 327's, then you have to tap into the valve covers or the non vacuum portion of the intake manifold. If the intake manifold you are using does not have the early style oil fill tube then the only option is to put a breather into a valve cover on a side away from the port into the push rod chamber of the engine. Some people try to use the old valve cover side vents that were used on early aluminum covers, however, they will not work with out a PCV in the system. After all is said and done the easiest way to solve the problem would be to deep six the script valve covers in favor of later model covers with baffles and the correct ports for breather and PCV's. A second thought is to do nothing about crankcase ventilation, just don't run the engine on the highway.
I like this idea, but Im thinking a normal rear axle vent (the kind with the crimped on cap) wont work, as it is made for letting pressure out, not pulling air in...there must be some sort of air breather out there that isnt "clunky", maybe from a small compressor, or...??
No oil tube fill vent then traditional would be a pcv in the manifold and a Mooneyes 90 deg valve cover vent on the inside of the drivers side valve cover behind the generator/alt (carb side not exhaust).
Here's mine, pretty simple. Comes out the side instead of the top. Air is coming in through the oil breather / fill tube. If you going to go for the traditiional sbc look, I think you gotta have a oil breather tube...
ZomBrian, you rock!!!!! Thanks for the heads up on this, it may have answered some of my questions, and I laughed my ass off to boot....Thanks
Tradrod, I may be reading this wrong. It sounds like you wish to use solid valve covers, do not want to use a manifold with a clunky oil fill tube, are running a pcv valve thru-manifold, and wish to allow fresh air in through an axle vent in the manifold. I see three problems, one is unfiltered air, two is not enough volume through an axle vent, and finally, are you planning to take of the valve cover each time you wish to add oil?
T.F. The rear-end vent was just brainstorming, kinda what I was after with this thread. I can add oil through the pcv hole in the intake rear, although not optimal. And if it doesn't use oil, this should be a very small issue. I think I can come up with something on the front of the intake to allow more air volume. Thanks for reading my posts to try to understand what I am getting at. TR
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