So you thought you could tune a Holley

[turbo2256b]

Here is another idle issue. When was the last time you replaced the Idle Feed Screw gaskets.
Here are a couple pics sorry about the quality. Think you can get the idea though. The top pair were in one of my carbs for a year I guess. They had shrunk and were impregnated with fuel. They were leaking air into the idle curcuit. Actually seating water around the outside of the needle due to the air velosity entering. With the engine shut off a trace of fuel leaked out.

Second pair were in for a week. Already leaking air, sweating and fuel soaked. This might have some to due with todays fuel vs cork.

The bottom one is made of neoprine and are available through Quick Fuel Technology. They fit tight and should last longer. Just finisned installing them and idle seems much better already.

[johnunit]

Ethanol does that. Easiest fix is to run premium.

[turbo2256b]

Ethanol does that. Easiest fix is to run premium.

I cant even run anything but premium. Fix is the right gasket. They fit tighter in the hole and turing the screw is harder. Be careful when turning the screw in as to tight into the seat and you just toasted a meeterig block.

[1987cp]

Lean spot off idle. What to look for to begin with.

This will require pulling the carb. Does anyone know what the Curb Idle Discharge Hole is? How about the Idle Transfer Slot?

As in, he should look for cloggage in the discharge holes or transition slots?

[turbo2256b]

As in, he should look for cloggage in the discharge holes or transition slots?

First thing is to look at the relationship of the butterfly to the idle transfer slot.

About .020 to .040 of the slot should be beneath the throttle blade never more than .060.
Typical if the carb is too big the throttle blade will be beneath the slot or cover it.
Too much too little of the slot can cause a off idle flat spot.

[Southern_Pride]

Its done it since it was new. Yes it runs funny because the butterfly's are open too far to make it idle. It idles in the transition circuit. I know what the problem is, just not how to fix it.

[turbo2256b]

Its done it since it was new. Yes it runs funny because the butterfly's are open too far to make it idle. It idles in the transition circuit. I know what the problem is, just not how to fix it.

The usuall fix is to close the primarys to only let .040 of the slot show below the blade. Then use the secondary throttle stop to open the secondarys to adjust the idle. I remove the secondary idle screw and install an alan head machine screw and a spring (if there is clearance) and rarely touch the primary idle speed screw again.



Notice the screw in the rear carb infront of the vaccum hose. Front carb is the same but vew is blocked.

[1987cp]

Does the socket-head screw make it adjustable without removing the carb?

[turbo2256b]

Does the socket-head screw make it adjustable without removing the carb?

Yes as long as there is clearance for it with the manifold / spacer combo. Can be done by hand in most cases. Sometimes some grinding can be done to provide clearance. A spring the right tension and it stays put.

This wont possibly fix all the issues but its were to start. Next might be the idle air bleed and or the idle fuel restriction.

[1987cp]

<----- wishes AFBs had secondary idle screws.

[Southern_Pride]

Ill play with it this weekend. Or maybe tomorrow at work when I'm bored.

[turbo2256b]

There is another fix to get the throttle blad in proper relation to the Idle Transfer Slot. This requires drilling a hole in each of the primary throttle plates. Some Holley carbs have this done from the factory. I will see if I can come up with some pics of this along with how to do when time permits.

[lincolnlarry]

off idle flat spot

The just off idle flat spot that responds to making the idle richer almost always means there is a problem with the accel. pump. Look inside the primary barrels. with just a tap of the throttle linkage you should see a strong full squirt right away. If not, there is slop in the pump linkage that needs fixed. Pushing the throttle down slightly more and the squirt gets better so no flat spot!!!

[Southern_Pride]

I drilled the holes. It helped a little. Not enough.

[turbo2256b]

I drilled the holes. It helped a little. Not enough.

Sometimes a combo of both is needed. The secondary stop mod is handy though as you never have to use the idle speed screw on the primary again which could through things off again.

The mods needed for the opposite issue not enough slot showing is fun.