Hey Kansas! Good to hear you are making progress.Usually its a combination of small adjustments to fine tune replacement components like a carb.The PCV valve is just  another example of trial and error.If you are looking to tweek the distributor Mr.Gasket sells a 2 pack of light springs for the 57-74 Ford distributor under part #925D.About $5.00 from most sources.You can use one or both together to change the timing curve of the distributor.The vacuum can on the distr.is also adjustable using an allen key through the opening where the vacuum line goes on.Be cautious and spray with wd-40 a couple of times before adjusting as you can strip the threads by "forcing"  it.Basically you should adjust the can to provide about 8 degrees of advance when vacuum is applied.If you are using the 13L slot in the advance cam you should end up with total  avaialable advance  of 42-44 maximum.Initial+mechanical+vacuum ie:10+26+8=44 total.This is about maximum total you should be aiming for all in by approx 2800 RPM.Playing with the mechanical advance spring tension creates a smooth timing curve.Something else for you to play with if inclined.What source of vacuum are you using for distributor vacuum advance?Fulltime(non-ported) or ported vacuum where the vacuum source does not apply until the carb throttle is opened?Some people find they prefer one over the other as far as how the motor runs.Another topic for discussion.

  

Glad to hear you're making good progress. Didn't mean to hijack your thread onto the PCV issue.

I worked on car today carb is so close to being right that most would let it be/ I also have a TBIRD valley pan with a small block chev pcv may be its to large I will try a small one this weekend /also will check out the distributor springs it also has a petronix ignitor system in it with new cap and plug wires/it can't be to far out of adj MPG has went from 13 with old teapot to to 22 and pulls a lot stronger

Just go by that application.80 Fairmont 4 cyl.Compare it with yours.Inlet size will be smaller and large end should be the same as yours now.

  

You assume right.

I get the concept of a closed system and the benefit of venting the oil cap straight from the filtered air from the air cleaner assembly. But I'm not worried about that right now, I don't put many miles on this engine.

I think I'll try a more restrictive PCV valve. Generally speaking I guess PCV valve sizes go roughly by displacement, but maybe I'll try something smaller. Mark, you mentioned about the 80s Fairmont/Zehpyr, you (or anyone) wouldn't happen to have a part number would you?

If there is a port on the carb for PCV it should be fine there-same as mine.If you found it ran better with the PCV unhooked(makes sense richer mixture) try either replacing the PCV with smaller(lower airflow) like I did or restrict it like Steve did.I found the PCV problem occuring at idle(inconsistent).At high vacuum(idle) the valve should be closed or very close to it working against the spring inside the PCV.Open too much or rattling like mine was gives inconsistent A/F mixture.I assume you blocked off the old road draft tube opening in the side of the block when you added PCV?

  

Mark changed his - probably the right move - but I just put an orfice in mine. The hose didn't fit tight on the Demon PCV port tube size either and I finally used a hose clamp on it to eliminate what I believed was a vacuum leak. And just as you say mine tuned right up after I started getting rid of some of the excess idle air coming in there. 

I made this little fitting - used the '64 truck PCV and bolted it on the back of the T-bird valley pan - put the orfice in the other end of the hose up by the carb. I'm sure there are some better ways to do it if you building a motor - Dutchy and Tim have been drilling and tapping a bolt hole on the back of the lifter gallery for a screw-in AC part - really looks PRO.

 
 Steve Metzger       Tucson, Arizona

Thanks Mark. Yeah, this got me thinking not only about making sure about the PCV size not being too big, but also about location. Right now (with vented oil filler cap and later TBird valley pan with hole/baffle at the rear) , the PCV valve is tied at the other end into the port on the rear of my Demon carb. I have wondered for awhile now if that's been leaning out my A/F. So I blocked off both carb port and PCV line for a brief test run and I swear the darn thing ran stronger. I remember reading somewheres that as much as 3-5 cfm can flow through the PCV valve, so maybe I would be better off re-locating it off of the carb...? Demons like it rich, right? So would someplace on the intake manifold be better, located near to the carb so all cylinders get an equal effect? Then drill and tap?

Exactly where would the best location be, and do you think it's worth the trouble? Any and all opinions appreciated.

Joey! I had originally installed a PCV from mid 60s Ford 302 thinking engine size was close to 292.I ended up using one from a 4 cylinder 80 something Fairmont-Zephyr.If you take yours to an auto parts place you can compare orifice(air inlet) size and find one smaller than yours now.Size controls the amount of air and mine was getting too much air messing up the mixture.Hope this is helpful.

  

What would be the optimum setup for a PCV valve on a 312? I have the B intake.