Thanks Jim for all you're doing for this site but now I am unable to search the forum. In rebuilding my 312 I drilled and tapped the block for a PCV valve per a previous post here. I kept the # of the PCV valve to use. AC CV726C. The auto parts store does not show this #. Does anybody know of another valve that will work or did I just have the wrong #. Thanks Dave V

SE Wis

After reading this thread a few times I realized you are talking about the fact that the Ford truck part (PCV) and the Chebbie part look alike - but are internally inverted......On the Ford part the suction end is threaded (where it screws into the intake manifold) and on the other GM part its threaded on the end that screws into the valley or valve cover. The check valve operates in opposite directions.

I used the Ford truck part on my bird (elbow in the back of the valley cover) and had to rubbber mount both ends with clamps to insure a seal. The trouble came when I found that the port in the Ford truck manifold provided a pair of rather small orfices to the intake tracts (now missing) - and my big free flowing "hosed" version did not. The PCV then became a large vacuum leak that interferred with getting a decent idle set-up. An orfice hidden in the hose calmed things down - but many of us have run across this.......

 
 Steve Metzger       Tucson, Arizona

Steve, just a bit of minutia, the Ford PCV valve screwed into a clunky fitting that bolted to one of the "mystery holes" in the back of the intake manifold. It was fashioned from a chunk of hex bar, threaded on one end and a hose barb on the other. The HD trucks used an inverted flare connection with attendant steel tubing and hose instead of just hose, BTW. Ford dropped the original style PCV valve years ago so I had to cobble up a "new" install. I have one of those adaptors and tubes (no valve though) somewhere in the garage. All in all, it was an inelegant design to say the least. Cheers