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By oldcarmark - 7 Years Ago
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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?
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By Joe-JDC - 7 Years Ago
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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
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By charliemccraney - 7 Years Ago
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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.
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By oldcarmark - 7 Years Ago
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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.
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By GREENBIRD56 - 7 Years Ago
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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.
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By oldcarmark - 7 Years Ago
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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.
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By 57RancheroJim - 7 Years Ago
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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.
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By oldcarmark - 7 Years Ago
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Joe-JDC (4/30/2018)
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
I assume You are talking about the Secondary Transfer slot? If the Slot shows at least .015" it should be OK as is?
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By Joe-JDC - 7 Years Ago
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oldcarmark (4/30/2018)
Joe-JDC (4/30/2018)
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 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
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By KULTULZ - 7 Years Ago
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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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By oldcarmark - 7 Years Ago
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I read the Installation Instructions on the Holley Website. Part of what it says is to adjust the Primary and Secondary Throttle Plates equally which is not possible because the adjuster screw on Secondary is no longer adjustable.
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By oldcarmark - 7 Years Ago
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I it back together Today. It runs great in Park. As soon as its put in Drive it almost Dies. Turning up the Idle screw still within proper Range for the Transfer Slot doesn't give sufficient Speed to correct Stalling. The Mixture Screws still work so I know I am not turning the speed Screw too far. Turning it any further gives excessive Idle speed in Park. This is the same problem I had with mine initially several Years ago. Float level is correct. I can't use the adjusting Screw on Secondaries because it is sealed. What if any is the effect of changing main Jets to bigger Size? I have 57's in it now and I have a couple of 60's to try if it has any affect on Idle? If the Idle Airbleeds are plugged from sitting around would that affect idle in drive? Any other suggestions? Timing is 10 BTDC with vacuum line off and plugged. Thanks
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By GREENBIRD56 - 7 Years Ago
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Mark, take a look at the point where the missing screw "should be" touching the vacuum secondary shaft linkage. That's where I have had to twist the sheet metal a bit to accommodate the need to open the secondary butterflies a bit. Its the stopping point for the vacuum pot - that keeps the rear butterflies from jamming when tightly closed. Seems like - this has been a year or three - I stuck a feeler gauge in there for a trial.
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By oldcarmark - 7 Years Ago
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Good suggestion. I will try that Tomorrow. I have another 390 which needs a rebuild and it has the adjusting screw in the Base and it does adjust the opening. Don't know why Holley changed the ability to use that Screw. I could probably swap the Bases but I don't have any Gaskets handy. I will try your Way.
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By GREENBIRD56 - 7 Years Ago
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Mark - This the stamped tab I am speaking of - and of course I could only find a picture of a carb that has the screw...... It would be nice if you could get the blocking screw out of the way and drill / tap for the proper item - but......
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By oldcarmark - 7 Years Ago
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Got it! Thanks Steve.
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By Ted - 7 Years Ago
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With the carburetor on the engine, I’ve simply bent the secondary idle tab appropriately to get more or less air at that point to get the primary throttle blades in a more conducive transfer slot positioning. This has eliminated the need to pull the carb off the engine and do a bottom side screw adjustment. A pair of needle nose pliers has been used for that minor tweaking.
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By FORD DEARBORN - 7 Years Ago
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I'll try to post a couple pics. 1) Is a screw of the proper thread with spring & lock nut on a Holley 570CFM "Street Avenger" hot rod series carb. It's on a moderately built 302 with a lopey cam and in this case, the ability to adjust the secondaries on the fly is nice. 2) Quick Fuel uses an Allen set screw. Just my $.02 hope this helps, JEFF.............
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By FORD DEARBORN - 7 Years Ago
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The site would not allow me to post the secondary adjuster with the spring and lock nut due to improper format? Sorry, I'll try again later.
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By GREENBIRD56 - 7 Years Ago
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Mark, this is the illustration I referred to earlier - out of the old Street Demon instructions. Shows the carb inverted and setting the primary throttle position (with choke off) so that the transfer slot is appearing as a "square". The suggestion has always worked well so long as the rest of the Holley design carb is in good working condition. I believe you are already aware of this - but there are many that are not.
For "noobies":
The adjustment discussed above a couple of notes (opening the secondary blades a bit) is required when placing the primary blade in this position - and then maintaining that position - won't deliver sufficient air to keep the engine at idle. We are talking about a warm engine with the choke "OFF".
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By oldcarmark - 7 Years Ago
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Thanks for the Picture Jeff. Most Holleys have that also. Problem with the One I have is the Screw does not go through. The Hole is capped with a little Bump which I assume is the setting Holley has decided should work. The Screw won't back out so my other option is to drill it out and retap. I am going to try bending the Tab slightly and see if that works. I had the same problem with my Car initially as far as stalling in Drive. I never had to use the Secondary adjustment but I think the One I am working on may have to. Runs nice in park and then hardly at all in Drive.
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By FORD DEARBORN - 7 Years Ago
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I posted that pic thinking you probably would end up drilling and taping. The pic I really wanted to post I couldn't. It was simply a screw with a spring and a jamb nut which made it very easy to adjust on the fly. As far as dying when in drive, it may be a lean-out condition. OK when no load but when some load is applied, the mixture may be too lean to support it. I'm going to make a couple guesses here and please keep in mind I'm not a carburetor expert by any means. If it is a lean-out condition, it could be caused by a missing idle air bleed. May run at idle but with the added load in drive there would be too much air at that point possibly causing a lean-out. Or, a partially plugged idle feed restrictor may possibly have a similar affect. That is, can pass enough fuel at idle but not enough when in drive? It's unlikely both of the above mentioned jets would be missing/plugged at the same time but it may just take one to do this. I believe you did state the idle mixture adjustments were responding properly. It was mentioned in a previous post that a used/hand-me-down carb is of unknown pedigree so if, for example, any one of the numerous gaskets is not registering with ALL the ports, trouble will follow. I believe you mentioned main jets but they should have no affect on idle. At idle, it would be the idle feed restrictors controling fuel flow which you won't be able to change, only verify they are open, in your case. Hope this will help and sorry for my lack of computer skills regarding not being able to post that other picture, JEFF.....................................
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By oldcarmark - 7 Years Ago
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Thanks for the suggestions Jeff. I had similar thoughts regarding the Air Bleeds after doing some reading online. I am no Expert either so any Suggestions are appreciated. I will have another look at it. Maybe something is plugged. If these Carbs weren't so Expensive new I would have gone that Route .Everytime I look at new Ones the Price has gone up. Popular Carbs these 390's.
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By FORD DEARBORN - 7 Years Ago
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Carbs are getting more expensive but it appears the throttle body EFI units are coming down in price and getting better/more user friendly. Everyone I met who went that route claims they will never go back to a carb again. If my carb wasn't working so well I think I would consider the EFI route. So as not to steer this thread off track, good luck with finding the problem and please keep us unformed, JEFF.................
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By FORD DEARBORN - 7 Years Ago
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This is the pic of the modified secondary throttle shaft stop on a 302 build. Simple and worked well. 
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By oldcarmark - 7 Years Ago
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That's something Holley and others could do from the Factory. Would make the Carbs much easier to fine Tune.. That looks like a Spring with 2 Washers and a Locknut under the Base? What size did U tap it for?
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By GREENBIRD56 - 7 Years Ago
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Personally - I use the "Ozark sidehill" method - a replacement length of screw long enuff to stick out the bottom of the base plate - and be turned with needle nose pliers! Most four barrel manifolds have clearance at that particular spot under the mounting flange (funny thing). At first I tried the proper method, replacing with a bit longer socket head set screw - but fitting the tiny wrench on a hot shaking engine was often painful.
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By FORD DEARBORN - 7 Years Ago
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Your observation is correct. However, I did NOT drill and tap the hole. It's been a few years ago but I recall not having the proper size bolt for that application and had to select a bolt from the hardware store. It was probably metric. In any case, the hole and thread is stock from Holley. This 5.0 Ford installation allowed for a long bolt but the possibilities are many. Hope this helps, JEFF...............
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