That port is the access point for vacuum to the hydraulic/vacuum brake system on big trucks of the mid 50s.I guess it was possibly for the power brakes on 54-56 cars.

 

Paul,

Boonville,MO

I agree - its an early manifold - but the hole is correctly located, drilled and tapped........just like for a later model truck that had the PVC. I don't know the exact manifold application shown - the four teapot sized bore holes and choke are indeed from an earlier era - the port could also be for a brake booster for all I know. But the port has the right set of two small holes drilled into both sides of the "cross H" manifold which would work just fine for a PVC set-up.

 
 Steve Metzger       Tucson, Arizona

That picture looks just like where my PCV was on my 2 bbl truck manifold.

Kenny  Onalaska, Texas

I hate to disagree with a member who has provided such great information and innovation to this site, but I'm pretty sure that is not a PCV port due to the fact that the manifold is for a '54 or '55 Ford or Mercury teapot carb with the choke mounted on the side of the manifold. No PCV valves were offered in those years as the crankcase was vented to the atmosphere through road draft tubes. Please correct me if I'm wrong.

Marc

'54 Merc ragtop

Pt Townsend, WA   

                                                                                                                                   

This is the PCV port to which I refer....



its right out front on some manifolds, tapped for the screw-in valve - or an elbow

 
 Steve Metzger       Tucson, Arizona

Found this cruisin' on Epay. 400412329076

Dan      Kingman Az.      86409

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

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

That same part comes up for a 1966 Chevrolet C10 which does appear to be one of the applications for the AC CV726C. But as you say, it also comes up for the Ford trucks.

In the past, I think I've used this one:
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=CRB29281_0374686755
A hose from the fitting on the valley cover goes to the big end. The other end is 3/8, which then goes to the manifold somehow. In my case, it was through the pcv fitting on the carb. I think I know where that valve is so I'll see if I can verify the part number for it.


Lawrenceville, GA

Charlie I picked up one (Lee Filters, Filter Dynamics International - LV-17) from my local vintage auto restorers emporium that looks exactly like the picture you posted. It says its for a '61-'62 Ford V8 w/292 engine (plus a bunch of other applications). This one however has a miniscule little arrow that says the threaded end should point towards intake manifold. The price tag said $1.95 but they gave it to me and they had dozens of different valves, all old stock in original packages. I guess I could screw the threaded end into the manifold (with an adapter) and connect the tube end with a section of hose to another adapter screwed into the block, or I could go back and see if I can find one with the arrow pointing the other way.

Mark

1956 Mercury M100
1955 Ford Fairlane Club Sedan
Delta, British Columbia