I just put a 57 b intake and holley 390 cfm on my  55 with a stock 292 and A/T It had A intake with a 4v teapot before/ it sure rans alot better but I have a small stumble when I take off / so far I have check the float level,accelerator pump arm adj,move the pump cam to the #2 postion Im starting to think that maybe I need to replace the pump shooter which is a .25 but Im not sure which way to go. how can I tell if Im too rich or runing to lean? both can cause a stumble or do I need to change my pump cam? Also when my secondary open I feel a kick which I think is a flat spot I think a stiffer spring on the secondary will take care of that problem The cars has 20 lbs vac at idle, I have try runing the timing at 6 and 12 %  with total adv of 38% at 4k also the distributor was update a year ago and it also has a new fuel pump Im hope that someone has has had this same problem and can tell me what fix it

I am running a 390 on mine which is stock like yours.What main jets are you using?From the factory they are oddball.512.Switch to a 54 and see if that helps.If better try 56.Thats what is in mine.Try also bumping your timing up to 10-12.Y-blocks like more initial timing than factory specs.You should only need the pump cam on #1 hole.#2 and#3 generally are used on motors that idle at 900-1000 PM to compensate for the change in position of the throttle at the higher RPM idle speed.I would also have another look at the accelerator pump arm.The arm should  move as soon as the throttle plate starts to move.Sometimes this adjustment is misunderstood.With throttle wide open(motor OFF) there still should be .015 before the pump bottoms out.You can verify this by using a .015 feeler gauge between the arm and the pump.If you have at least that amount of clearance you are OK.Sounds like you are pretty close to having it run properly.Little tweaking can make a big difference.Let us know how you make out.By the way I wouldnt worry about the shooter size.Should be fine as is.What idle speed are you running in and out of drive?One other suggestion-if you do not have one already a 1 inch phenolic spacer will help keep heat off the carb.

  

I have had the same situation in the past. I eventually went to a Demon carb, but that was as much because a friend wanted my Holley 390 as anything else.

A couple questions to better understand...

You say your vacuum is 20 lbs at idle which is pretty good, but does it drop to zero (or close) when you punch the throttle, and then return?

What about A/F mix...how are your spark plugs looking?

What color pump cam is it? I believe Holley's orange cam is the hottest on this carb for off the mark response.

You said your distributor was updated...what is it? Does it have mechanical advance, or vacuum? I think that a properly set up vacuum advance will generally give you a more responsive low end than mechanical, all other things being equal. Mechanical distributors rely on centrifugal force and are a bit slower to kick that advance in. If it is mechanical, you may be able to adjust the distributor springs (make one weaker than the other) to speed up the advance curve for better low end throttle response.

Throw a little more initial timing at it (say 14 BTDC) and see if that yields a better low end response. This may help you to better narrow down what's going on.

when throttle is punch it drops and then comes back

plugs are a light gray

distributor has vacuum

kansas - I'm glad you got yourself a new distributor, the old full vacuum Load-O-Matic just won't work right at all with the later Holley. When you reported trying 12° initial - and also a top mechanical advance number of 38° at 4000 rpm - I'm going to assume those two numbers belong together? And that's with the vacuum pot out of the circuit? Plugged at the carb / disconnected from the vacuum pot? That would indicate to me that you've go one of the "newer" Motorcraft distirbutors and the centrifugal advance stop is in a "13L" slot - which gives you 26° at the crank plus the 12° initial = 38°. Hope this is right.

I believe that you ought to start out tuning by establishing the "mechanical" part of the ignition advance. So 10°-12° is good for initial on a stock cam - and 36°-38° is good for the full amount (summed initial and centrifugal). The 4000 rpm where you now rev to get it all - is a problem - the engine will like it much better if its all in somewhere down around 2800 rpm (some engines even lower). Find a source of a weaker spring to substitute into the centrifugal advance mechanism - and figure out how to get down in there to change it. A little experience with disassembly of these things goes a long way.........usually much easier to do - out of the engine.

 

This one has the two springs out - but you will normally find one that's pretty stiff and the second fairly weak. If you can find a match for the weak spring - that will work for a trial. Reassemble the distributor in reverse order of steps - and set the points before you put it back in the hole. With some luck - when she's all back together you will be at a usable full advance rpm. It is nice to find or know someone with a SUN distributor machine to set this up  - but you can do it in the driveway (if weather permits) - and that's the way I learned - trial and error.

Anyway - when you have a useful "curve" in the distributor - then you tune the carb. The reason being - adding advance will always lean the engine - without you touching the carb. That is how the vacuum advance pot works to increase economy - adds advance when there is low load / high vacuum and leans the system out.

Mark is right - you will probably need to get some bigger primary jets - and the sizes he mentioned are a good start. This diagram shows how the primary throttle needs to sit on the "transfer slot" - its the way the Holley carb goes from "idle" to "run"....

The plan is - to get the carb to run the engine smoothly off idle to cruise without a "lean stumble". Do you have a PCV valve hooked up to the carb - Mark found his to be a big source of (extra) air to the carb - air without fuel = lean. Make sure its the right size if you have one - too much air through the PCV will fight you.

 
 Steve Metzger       Tucson, Arizona

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

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.

  

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.

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

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?