Are you running a vacuum advance on the distributor? Do you have vacuum on the dist line at idle? If the answer to the first two questions is yes, and you are using the factory distributor, take the vacuum line off the distributor and plug it. Then go for another test ride and see if the problem goes away.

If the problem goes away unplugging the vacuum line, I think you are over doing it a little bit on your initial timing setting. If you want to leave it that way, you will need to leave the vacuum advance unplugged. If you want to plug the vacuum advance back in you need to turn the timing back a little bit till it straightens out. If you want your cake and eat it too, you will have to dig into the distributor and adjust some things and get a adjustable advance unit to get it all dialed in.

 

 

This seems like an idle mixture problem, sounds like you are getting a lean spot on the transition from idle to main circuit. I assume you have reverse-idle carb. So try turning in the idle mixture screws clockwise 1/4 turn at a time and test in between to see if it makes an improvement . I highly doubt this is a timing issue. Your base advance is a bit high and the base idle is also high but that would not give you a light throttle acceleration bog. .

 

 

Ya this seems like the most logical conclusion 20 years ago no ethanol fuel today ethanol fuel so it would not be surprising if the carb needed tweaked a bit.
. If yours is not a reverse idle circuit carb you will turn the idle mix screw counter clockwise to richen it up.
Reverse idle carbs have rather blunt idle mix screws.
In Reverse Idle circuit carbs the idle mix screws control air flow in ones regular ones they control fuel flow.

A quick way to check to see what you have is wind the screws all the way in if the engine fails to stall it is reverse idle.

 

 

 

There is a minimum air setting for the rear butterflies. This is so the rear of the carb always uses just a little fuel so the fuel in the rear bowl does not go stale. Getting it right can be difficult though, you have to unbolt the carb and hold it up in the air to get to the screw on the aftermarket Holleys. Not sure about the Ford/Holley carbs though. If you turn the carb over to make the adjustment, fuel goes everywhere.

 

In a Holley carb the power valve helps in that "no man zone" between idle & main circuit.
Check what your vacuum is in gear at idle, take that and cut it in half and that is a starting point for the PV.
Most rebuild kits and new carbs come with a 6.5 hg PV you will need to go up or down from there.
Dave ----

 

Yes if you are not getting any adjustment on the idle mix screws then the primary throttle blades could be exposing the transfer slot and be pulling fuel through the transfer slot instead of the idle port.. Before you adjust anything pull the carb and check to see how much the primary's have exposed the transfer slot. If they are exposed open the secondays a bit this will necessitate the closing of the primary's. Ideally you just want the lower edge of the transfer slot to be visible below the primary throttle plate but not the slot it;s self. I tend to set the primary's as above and adjust the idle with the seconday's I replace the slot set screw with hex head one and then you can adjust it with an allen key without having to remove the carb as that bit over hangs the mounting base on most intakes. As Franklin stated you want some fuel movement through the secondary bowl so the gasoline does not go stale. Some people will drill a small hole in the primary throttle blades to get the primary's to close more but I was never a fan of that. Mind some carbs came like this from the factory.
This is one of the grips I have about the Holley is setting the secondary idle position. Holley does sell an external secondary adjustment screw bracket that will allow you adjust the secondary's without having to pull the carb. It is made for mech secondary carbs but can be fitted to most all Vac secondary carbs, on some carbs it may need a light tweaking but for most it just bolts on.. It is stupid expensive for what it is see below ,I prefer the $1 secondary set screw change myself. If the bracket was reasonable I'd just buy it but not at that price.

https://www.holley.com/products/fuel...e/parts/26-137

 

Read the first post again he is getting this issue under lighter throttle, so he is not likely not relying on the PV for enrichment if it is sized correctly. No issues under harder acceleration when the PV would be put in to action..And the fact that he is getting no measurable adjustment on the Idle mix screws points to something other than the PV. Also the no man zone between main and idle is what the accel pump is for. Under lighter throttle application the transfer slot does this job. The PV is to provide enrichment primarily at speed and you open the throttle where the accel pump may not move any measurable amount or enough fuel. Plus the PV feeds the boosters if no fuel is moving through the boosters/ Man circuit the PV does nothing it could be full open at idle and just off idle and will have no impact at all until fuel starts moving through the boosters/main circuit.

 

I remember reading in one of my Holley books, that the transfer slot is like a rectangle, and that the throttle butterfly should cover it up so the slot looks like a square.

There are so many variables in this. I hope he doesn't have a vacuum leak or any other problem that is causing him to have to open the idle adjustment up too far. That can foul everything up also. And I have also opened up the secondaries too much, and really fouled things up. That adjustment back there is touchy.

I think in the rebuild kits they tell you to back it off till the secondary butterflies fully seat closed, and then turn the screw in a certain amount of turns. But I have had this be too much also. If you find the engine acts like it has a huge vacuum leak and you can't get the idle to come down after you adjust the secondary stop screw, you have opened it up too much.

 

The Transfer slot is exactly that a slot, but this rarely works out and you end up with high idle's and little adjustment on the mix screws plus is may mean completely shutting the secondaries on some carbs on higher duration cams with low idle vacuum you may need to uncover the slot a bit to get a bit more fuel to get the engine to idle properly. But on cams that provide a good vacuum signal at idle you may lose idle screw mix adjustment by uncovering the slot. The opinions about this vary some advocate drilling the primary butterfly's instead. My take on it is It depends on works best for you application. Example on an engine that may be under carbed but with a high duration cam you will probably want to uncover the slot. EG 429/460 with a 600CFM carb. Where you are over carbed eg a 289 with a 600CFM carb and high duration cam you may want to drill the primary throttle blades or open the secondarys more.. There is no one answer that will cover all applications.

 

If you read his first post he has the idle at 900+ RPM
This is now out of the idle circuit and most likely why the idle mix screws do nothing.
With all the Holleys I have played with I have never needed to adjust the secondary butterflies to get the idle side to work.

Also if the vacuum changes the PV will come into play and more so if it is not sized right.
Holley books also say it is used between the idle & high speed circuit.
Because he is stomping on the gas he is covering the issue that he has when going easy.
The vacuum drops and the PV opens and he goes from idle to mains and nothing in between like going easy.

He needs to get the idle speed down so the mix screws work, check vacuum and adjust the PV as needed and he should be good.
He should also disconnect the linkage to the secondary side and tune the primary side as a v2 carb.
Once it runs good as a v2 hook up the secondary and tune with the different colored springs if vacuum secondary.
Dave ----