Hey everyone, first a disclaimer:

For starters, I'd get another gauge. Next question, are you using manifold vacuum, or coming off a ported source? I'd think at 7", you'd need more like 1200 rpm at idle. Someone with a real race car would know.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

First of all, get a known good gauge and check the engine.  Just because it's a Snap On doesn't mean it can't be bad.


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

Okay, Okay, I'll buy a new gauge…and here I was thinking I was all slick because I bought a snap-on for only $10. lol Here is where I am taking my measurements from. Keep in mind there is a T here. I am using the side that feeds to my wipers, the other side goes to my pcv valve, which I am leaving connected:

Temporarily disconnect and plug the PCV connection. If the vacumn goes up, check which PCV valve you're using. A vacumn leak that size thru the valve would also answer the hesitation, as that much airflow (big vacumn leak) would cause a lean condition. I've done PCV valves into the manifold like that, but never saw such low vacuum. Run a search here, recommended PCV valves will show up. Most times, the valve runs either into the carb, or a drilled adaptor plate between it and the manifold.

Spell check doesn't seem to know how to spell vacumn? Vacuum? Should have paid more attention in school, I can't either.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

You are spot on! I couldn't help myself and I went just now to go test your theory. I plugged the pcv valve with my finger and vacuum shot up to 17! Hooray! Now I just need to figure out which pcv valve I actually need. Thanks for your help!

You can insert an orfice in the line to the valve and that will get you moving in the mean time. My outfit is using the valve for a 60's 292 truck and it is way too much flow when connected directly to the later style carb base port. But has worked fine after the orfice was installed in the hose.

 
 Steve Metzger       Tucson, Arizona

If you are using the type of PCV Valve that goes in a grommet in the Valley Cover I ended up using one for a 78 or so 4 Cylinder Fairmont/Zephyr.I first one I tried was for a 302 Ford and it was allowing too much Air at idle.Trial and error or try a restrictor as was suggested. 

  

Steve, as the restricter guru, what size orifice did you install?Thanks.



Mark

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

Thanks for the help everyone. I too would like to know what size restrictor would be good to start with. The only one I can find for sale is a Dorman 3/16. I will try a smaller pcv as well.