Throttle linkage problem.........

[sidevalve8ba]

I have been struggling with a nagging problem in my throttle linkage for some time now and I could use some advice from you folks. I have twin 94's on an Edelbrock intake on the '50 mercury engine in my '32. I am using the stock gas pedal and a modified link to the front carb. The carbs are linked together on the driver's side. The problem I am running into is a, for lack of a better description, hard spot in the throttle right off of idle. In other words, I have to push the pedal pretty hard to get past this "hard spot" to pick up speed and then it really takes off! Too much! Obviously it is binding up right off of idle but for the life of me I cannot find out where. I have lubed and inspected the linkage from one end to the other. What am I missing?

[Ken/Alabama]

Does it do it if you disconnect the linkage between the two carbs? Also, looking at the photo of the drivers side linkage it appears the front carb is ahead of the rear. Make sure the butterfly in the rear carb isn't closing off before the front causing a binding situation.

[JSeery]

Any chance the throttle plates are sticking in the throat of the cabs? I would remove the connecting linkage and check each carb separately to see if one or both of the throttle plates are hanging up.

[George/Maine]

You could disconnect the carb link with spring tension added to free one.
Now play with the idle speeds to be equal one carb at time.Put linkage back on.
See if that help.

[sidevalve8ba]

Ken, I will try running it on just the front carb to see if it is free then. That will tell me something if it is.

JSeery, I checked the throttle plates first thing to make sure they weren't binding or hanging up. No problems there.

[sidevalve8ba]

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Originally Posted by George/Maine

You could disconnect the carb link with spring tension added to free one.
Now play with the idle speeds to be equal one carb at time.Put linkage back on.
See if that help.

Would using a Uni-Syn do the same thing?

[Karl Wolf]

(1)Put the return spring on the other side, where the two carbs connect. Maybe.
(2)I noticed the sharp angle of the right side, where the first part of the linkage hooks to the carb. Changing this angle will help, more toward 90 degrees. Better leverage for the start of the pull.

Karl

[rich b]

^^^
I was thinking the same thing; that angle on carb connection looks pretty sharp; funny geometry could result in the foot pedal action you describe.

[19Fordy]

I don't know anything about solving your problem
but would some type of BELL CRANK arrangement help?

[weemark]

Originally Posted by Karl Wolf

(1)Put the return spring on the other side, where the two carbs connect. Maybe.
(2)I noticed the sharp angle of the right side, where the first part of the linkage hooks to the carb. Changing this angle will help, more toward 90 degrees. Better leverage for the start of the pull.

Karl

im not sure changing that linkage and the angle it sits at would help, I run both my sets at 45 degree and have no problems at all with throttle control. mine are like the ones below

[weemark]

Originally Posted by sidevalve8ba

Would using a Uni-Syn do the same thing?

you could use a uni-syn to synchronise them - to do it properly you need to disconnect the carbs from each other and set up the idle on them individually. once you have each carb flowing the same then put your linkage back on.

[Kruzn40]

Your problem is that your carb connection wants to travel in an arc and you are pulling on it at idle in a more linear motion. By this I mean that your carb connection is slightly over center towards 1 oclock and you have to force it past noon towards 11 oclock before it will travel smoothly around the arc. Modify your linkage connection at the carb so that you are pulling over the top of the arc instead of thru it. You could accomplish the same thing by raising the connection point at the firewall but you may lose some WOT motion by changing that end.

[V8COOPMAN]

Originally Posted by Kruzn40

Your carb connection is slightly over center towards 1 oclock and you have to force it past noon towards 11 oclock before it will travel smoothly around the arc. Modify your linkage connection at the carb so that you are pulling over the top of the arc instead of thru it.

You sure you're seeing this correctly? The picture shows the connection at roughly the 5 o'clock position in relation to the butterfly shaft that it rotates around (right where the return spring hooks-on). DD

[Kruzn40]

Originally Posted by V8COOPMAN

You sure you're seeing this correctly? The picture shows the connection at roughly the 5 o'clock position in relation to the butterfly shaft that it rotates around (right where the return spring hooks-on). DD

OK, to be more precise let's use 5, 6, and 7 o'clock instead. The theory remains the same.

[51 MERC-CT]

Originally Posted by Kruzn40

Your problem is that your carb connection wants to travel in an arc and you are pulling on it at idle in a more linear motion. By this I mean that your carb connection is slightly over center towards 1 oclock and you have to force it past noon towards 11 oclock before it will travel smoothly around the arc. Modify your linkage connection at the carb so that you are pulling over the top of the arc instead of thru it. You could accomplish the same thing by raising the connection point at the firewall but you may lose some WOT motion by changing that end.

Sorry but I can't see how raising the connection point on the firewall would improve the condition?

[51 MERC-CT]

Is it possible that the tang of the return spring is causing binding where it is attached?

[weemark]

Originally Posted by 51 MERC-CT

Sorry but I can't see how raising the connection point on the firewall would improve the condition?

I think he means lower it

[sidevalve8ba]

I have tried the spring on both sides and can see no difference.

I appreciate the ideas you all are coming up with and I am looking forward to trying some of them out in the AM when I get to the shop. It always seems to help to have "another pair of eyes" on a problem. Thanks guys.

[Kruzn40]

Originally Posted by weemark

I think he means lower it

Not being intimately familiar with a 94 carb and the linkage attachment point not being clear in the small photo, I assumed it to be at situated above the throttle shaft instead of the bottom. In this case you obviously want to lower the linkage rod to achieve as near 90 degree angle as possible with respect to the throttle shaft.
I have solved this exact problem on a couple of occasions by changing the rod geometry.

[uncle max]

Loosen the mounting nuts on both bases, adjust the linkage until it's smooth, then re-tighten the mounting nuts.