I picked up a lightly used Holley 390 CFM 8007-0 Carb for my buddies 56 to convert His Teapot as well as changing the Distributor. I have the same Setup on mine.Having a little trouble getting it to Idle in Drive. I had the same problem with mine initially until I got the Transfer Slot adjusted properly. I pulled this One back off Today to check the adjustment of the Throttle Plates in regards to the Transfer Slot. Made a note of how many turns of the screw from not touching the Lever until the correct adjustment for the Slots. I was going to make the secondaries adjustable also by changing the set Screw to something I can turn without taking the Carb back off. This newer Version of this Carb has the adjuster blocked off on top of the Baseplate like Holley doesn't want You to play with it. All the other older Ones have that adjuster open so You can use it. I seem to remember it was Holley who suggested using that Screw to ad a little more air and leave the Primary Speed Screw alone when properly adjusted for Transfer Slots. Has anyone actually used that Secondary adjustment when using One of these Carbs on a stock Motor? I didn't on mine.
I am going to put it back on as is and see if it works better now with the proper adjustment. If I cant get it working properly I guess I will have to drill and Tap the Baseplate. I just wondered if anyone else has had to use that adjuster? 

  

The idle transfer slot is there for a reason, and it needs to be adjustable, or you need to bend the arm to get the initial start-up position correct.  I have found the slot needs to be at least .015", but .018", or .020" works for different carbs.  Too much slot showing and it will idle too fast, not enough, and it will stink from being too rich.  Joe-JDC

JDC

I don't have an answer to your question.
Since it is a used carb, the first thing to do is to ensure that it is setup at its baseline, factory tune so that you have a good starting point.  There's no telling what a previous owner may have done.


Lawrenceville, GA

I am well aware of the requirement to adjust the Throttle Plates for correct amount of Slot showing. Just wondered if anyone has actually used the Secondary adjustment on a stock Engine. I seem to recall Holley suggesting using that adjustment and now they have starting making that adjustment unavailable. The Carb appears to have never been opened up. Main Jets are 512 which is what they come with from Holley . I changed them to #57 which us what I have in mine. I am going to put it back in Tuesday and see if it will work now with the Throttle Plates adjusted.

  

Mark - I don't have the illustration right here with me - but the old street demon (Holley 4160 derivative) had an illustration in the set-up sheets that showed the transfer slot at initial adjustment. What they were suggesting was that the height of the slot opening be the same as the slot width - so what you would see was a "square". Will try to find the illustration tomorrow and put up on here again. It works.

To adjust the secondary butterflies and gain idle air, there used to be that hidden screw accessed from under the base plate. An illustration was in the old 390 set-up directions showing its location right beneath where the secondary vacuum pot attaches to the secondary shaft. Why they would do away with such a convenience I have no idea - but I have found carbs that had the tapped hole - but no screw - and I put one in there. When there was no screw - and I had to get the darn thing running without a replacement  - I resorted to (delicately) tweaking the sheet metal secondary throttle "closed" stop with needle nose pliers. Just enough to stop the blades open enough to get the required idle air.

What I don't know: is if a design change has done away with the bleeders for the back bowl - that dribbled fuel into the back venturis and gave the tweaked air leak a bit of fuel.    

 
 Steve Metzger       Tucson, Arizona

Hi Steve!. The threaded Hole is there, the Screw is inside, but where it used to come out is a little cast "Bump" just enough to open the Plate the minimum amount to keep fuel running in the Secondary. And the Screw will not come out even with a decent size Screwdriver with narrow Blade. It appears that Holley doesn't want anyone messing with the Factory Setting.

  

I've ran the same Holley 390 on both of my 292's. One completely stock and I never touched the secondary adjustment. The other engine has an Isky E4 cam and I only needed to increase the main jet size but never touched the secondaries..
Have you checked the float level? Thats the first thing I do before making any other adjustments.

I assume You are talking about the Secondary Transfer slot? If the Slot shows at least .015"  it should be OK as is? 

  

Always check the transfer slot before installing a Holley.  It is the BASIC start to all adjustments of the start, idle, and idle speeds.  If it is hunting an idle rpm, then give it more slot showing, if it is idling too fast and you can't control it with the primary blades adjusted to closed, then decrease the slot.  .015" may work, but .018" may work better, it is something you have to actually adjust to find the best quality for your combination.  It doesn't matter if it is a 390 cfm carb, or a 1050 cfm carb, they will all respond the same way to basic tuning and idle quality unless you have one of the reverse idle circuit carbs.  Joe-JDC



JDC

The CARB may be EMISSIONS CALIBRATED where the usual adjustments are limited.

Maybe run the LIST NO through HOLLEY and see if a TECH SHEET shows up?

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