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.

[Terry,OH]

There seem to be a number of small items that may be contributing to the problem. The original return spring on the firewall throttle linkage doesn't even appear to be touching the arm. Can you get full throttle movement? I believe the arm should be slightly forward, yours appears to be nearly vertical. I use the same throttle arm ends and yes the return spring connection location could add to the problem. These ends could be their own problem do not tighten the adjustment screw at the end of the ends too much. Make sure they are not binding when the throttle moves. At rest you want the linkage on the drivers side to be forward and at full throttle it should be rearward as shown in posting #10 above. There are other good ideas above.

[drolston]

Just for fun, disconnect the linkage from the carb and try the pedal to be sure the pedal isn't binding or the pedal push shaft is not hanging up where it goes through the floor board. And while you are at it, shoot some WD40 on the shaft and spring where it traverses the firewall. If all of that is smooth, press on to the most likely suspect, - throttle plates.
- It is critical to be sure that all throttle plates are perfectly centered in the bores, laterally and fore/aft within the slots in the throttle rods. I polished the bores to smooth off any burrs in the surface. Also finely sanded the sharp edges of the throttle plates. Then, with fingers pushing the throttle plates tight closed to center them, tightened the screws that hold the plates to the shaft. Shine a light through the bore from one side and look for light shining through around the throttle plates on the other side. There should be practically no light, and if any it should be evenly spaced left and right and fore and aft. The final test is to close the throttle hard with the throttle lever, and then see if there is any binding at all when initiating opening; if so - do over! If no binding, then you can carefully ding the screws holding the throttle plates, so the screws do not back out get sucked into a cylinder. Then check again for sticking, in case you bent a throttle shaft while crimping the screws.
- When fastening the carbs to the manifold the studs might allow a little slop in alignment; be sure they are centered. Maybe run a straight edge across the bases on the driver's side.
- Do not yet link the carbs together. Lightly fasten the manifold on the engine and hook up the linkage to the pedal. Adjust the linkage so that with your foot off the pedal, the linkage is about 1/2" too long from aligning with the throttle lever ball on the carb. You need that much spring pressure pushing the throttle closed at idle. If there is any binding, or sticking, it is in the linkage from the firewall to the carb.
- Then take the manifold to the bench and proceed to set up the linkage to the secondary (rear) carb. With the linkage not yet connected, the levers on the drivers side should be about 40 degrees forward of carburetor vertical, and as close as you can eyeball or measure to being the same angle on both carbs. At full throttle, both levers will be approximately 45 degrees to the rear of vertical. If at this point you encounter binding, let us know and we will advise further.

[Charlie ny]

SV,
Check 'weemark's' 97 setup,the arms on your carbs should be setup like that only remember the 94's work opposite. I believe the driver side arms are too vertical.
On the pass side....now don't laugh, I would bend the connecting link (between the front carb and the firewall arm) so that the link assumes a more level attitude as it approaches the front carb. Subtle changes will make big improvements.
With all due respect to drolston , I can assure you the throttle plates are good. As you received these carbs both were syc'd and idle speed set. Keep in mind the plates are
cracked open ever so slightly to achieve idle speed.
Charlie ny

[V8COOPMAN]

Originally Posted by Charlie ny

SV,

On the pass side....now don't laugh, I would bend the connecting link (between the front carb and the firewall arm) so that the link assumes a more level attitude as it approaches the front carb. Subtle changes will make big improvements.

With much due respect to you Charlie, you can bend that connecting link in any shape you want. You can even bend it into a pretzel, but it will still effectively exert a pulling force in a straight line between the two existing "attach" points, exactly like it does now........simple physics. DD

[Charlie ny]

Coopman......yikes......thanks for lettin' me down easy. I'll go back to Miller Lite.
I'm going bed.
Charlie ny

[Charlie ny]

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Try pulling from the rear carb ? It's worth a shot.
Charlie ny

[Brian]

I've had the same problem with 94's in a dual application... I think if you try Uncle Max's suggestion it will help...however, how I got around it was to link up both carbs on both sides, ie, use a link on the regular foot feed side, use another link on the 'hand throttle' side, so that there can be no 'racking/twisting' whatsoever in any throttle position.All arms need to be same length and set up at same angles, and make the links adjustable for fine tuning, because, ultimately, they'll need to be identical lengths. I also sweat a ball midway along the regular foot feed link, and attach my throttle rod to that, which evens up the pull. Bit of fiddling about to achieve a super smooth action, but it is time well spent once it's all running good.

[weemark]

I think the only way you are going to get a smooth operation is to change to a cable throttle. your throttle rod mount on the pedal side is always going to be higher than he ball on the carb which means the rod is pulling at the wrong angle for it to work smoothly.

[Charlie ny]

SV,
I've found a 94 throttle arm for a '49-'50 Ford with Fordomatic that positions the
ball at 6 o'clock with the carb full closed and 8 o'clock full open, I think that will
accommodate your issue. Get back to me [email protected] no charge.
You can see the current arm is attached with a 6-32 button head screw so switching
is a no big deal thing.
Charlie

[V8COOPMAN]

Originally Posted by Charlie ny

SV,
I've found a 94 throttle arm for a '49-'50 Ford with Fordomatic that positions the
ball at 6 o'clock with the carb full closed and 8 o'clock full open, I think that will
accommodate your issue. Get back to me [email protected] no charge.
You can see the current arm is attached with a 6-32 button head screw so switching
is a no big deal thing.
Charlie

NOW you're on to somethin' GOOD! DD

[sidevalve8ba]

Email headed your way Charlie

[kiwitony]

This is a typical problem with the holley, because at idle the throttle link is at 5 oclock on opening to 6 oclock the arc it travels trough means the rod in theory needs to get longer, from there on a straight pull untill nine oclock, were if it need to go further is going away again. On the original set up the return spring was on the pedal shaft and no pressure on the carb when the accelerator was pushed the little spring loaded end cap would momentarily stretch through the 6 oclock position and then close up when it had a straight pull. I would put the return spring on the accelerator pedal inside on the fire wall. Lowering the cable to get closer to a right angle[90degrees] to the throttle shaft will help, but too low you won't get full throttle. As others have said maybe a light return spring on the other side as a safety thing. If I knew how to do a sketch and post it I would as it would explain it a bit better. Hope this helps.Tony.

[weemark]

for purely aesthetic reasons I would change the arms on the rod that joins the carbs together on the left hand side for proper shop bought arms and use the Stromberg snapback springs(part no. 9154k) on the throttle shafts then you can remove that big spring all together - they work really well and are nearly invisible once they are installed and tidy things up no end. like the ones in the pic below

[birdball]

On my dual carb setup, I've noticed that with good return spring pressure on both carbs, it forces the spring loaded ends of the throttle linkage (ball mount ends between pedal lever and carb lever) to flex until they bottom out before any throttle action happens. The result is wasted motion for the first bit of pedal travel and a weird feel of lag.

That being said, I'm voting for the 5:00 position being the issue, perhaps aggravated by your throttle linkage flexing...