57 Thunderbird - Throttle doesn't move with pedal

[atldan]

Hello -
We have a 57 Thunderbird here in the shop that's had a full restoration. A Holley carb has been installed and it appears to be the same design as OEM - just a new one. The problem we are having is that pushing the pedal in the car doesn't move the throttle plates. It activates the kickdown, but not the throttle. If you press the pedal lightly, you can get the throttle plates to open, but not all the way.

Any guidance you can offer would be most appreciated. (Yes, I searched!)

[ward 57]

Can we get a picture of the actuator? It sounds like something has slipped or broken or mal adjusted. That's where to look if the kickdown linkage is working.

[ICON 1956]

Check the choke plate linkage inspect the fast idle cam on the side of the carburetor. Are these lubed ? Do you have the Shop manual for the 57 ?The automatic choke is provided with an adjustment to control the reaction to the engine temperature.
By loosening the three screws on the choke housing that retaintain the cover it can be turned in a clockwise direction which will require a higher engine temperature to fully open the choke plates. Turning the the cover in the opposite direction will cause the choke plates to fully open at a lower engine temperature. This is a lean direction.....

[ward 57]

Good point. I was assuming he was talking about the throttle plates and not the choke plates.

[Rusty57]

Try this procedure.

http://www.squarebirds.org/Manuals/1960 ... talogs.htm

On our '57 the "grasshopper leg" downshift mechanism had been locked. There was a bolt and nut in the slot so the throttle could not move through its full travel. Pushing the throttle to the floor did not open the throttles completely. It twisted the bell crank attached to the firewall. I had to remove that bell crank and "untwist" it.

I set the linkage to the dimensions described in that document. I did have to back off the kickdown linkage a few turns to reduce the harshness of the full throttle upshifts.

Make sure you follow the correct sequence. Disconnect the throttle and kickdown linkages first. Set and hold the accelerator pedal in the correct position. Then connect the throttle linkage and make adjustments to get the correct throttle action. Then work with the kickdown.

[Jimntempe]

You may have the same issue my car had, not sure but take a look at the photo. I think Rusty had the same issue and I've talked to one other person who had this issue too.
The issue is that bell crank shaft separates from the "plates" that comprise the downshift mechanism and throttle crank. Mine was repaired by welding and was welded a bit off center and that made the downshift slot bind which I fixed by widening the slot. The intent of the design is that the gas pedal will be able to open the throttle ALL the way BEFORE the transmission rod (TV rod) reaches the point of "kickdown". That slot is the "maneuvering room" for getting the TV rod in just the right spot after the throttle is fully open. Based on what I've seen on mine, when it's dialed in and you have the pedal to the floor you will wind up with the slot-pin somewhere around the middle of the slot.
Anyway, maybe it's the same issue, maybe not.

[atldan]

Wow! What a great forum - thank you for all of the responses.

Further digging in, the replacement carb is a Holley 4160 with electric choke. Try as I might, I cannot get the OEM rod to actuate correctly. Here are some images and a video highlighting the problems:



link to video

[Joe Johnston]

This is what mine looked like with an aftermarket carb. Very similar to yours. Worked well.

[Rusty57]

Great additional posts. Pictures do help.

Jim and I shared information to help us get the things adjusted correctly. We both did have issues with the “lost motion” function of the kick-down linkage.

There is one item that caught my eye in both antidan’s and Joe’s pictures. In atidan’s picture the throttle link itself is adjusted to full length. In Joe’s picture it appears that he has fabricated his own throttle linkage. Yes, I did. The AFB style carb is wider. Also had to make the brass collar to allow the aircleaner to clear.

The key is that the stock throttle link might not work with a 4160 due to the location and travel range of the point where the throttle link connects to the throttle mechanism on the carburetor.

This is one of those “get back to the basics” projects. As I suggested earlier, disconnect all 3 adjustable links in the mechanism. (Yes, there is a 3rd short vertical link between the bell crank that is mounted on the firewall and the kick-down mechanism bolted to the manifold.)

The very first thing that would do is make sure that you can manually operate the throttle on the carburetor. Make sure it goes through the full range of travel without binding and that the secondaries will operate like they should. You might need to manually activate the secondary vacuum diaphragm. Next I would determine if the engine runs as expected with the throttle link disconnected. Manually operate the throttle on the carb to see if it will come off the fast idle cam as expected.

Then follow the procedure in that pdf file. The clue that I had a problem with the bell crank was that I could not get the proper pedal height. After I “adjusted” the bell crank to get the correct pedal height the rest of the process worked as expected.

[atldan]

Thanks all - the engine runs excellent with the new carb and is very responsive when manually activating the throttle via the arm on the carb. I'll dig in to the geometry involved and see if I can suss anything out to get it to function correctly. Thanks for the suggestions (and keep em coming!) This particular 'bird is a European model that was shipped back with the owner when his tour ended overseas. He bought it new and it's been here in the shop for a full frame-off resto. I just finished adding EPAS power steering to it and have shifted my focus to getting it running perfectly. Then install the windshield, and finally try to fix the !*(&%* leaking trans pan. 3 gasket changes later, and it still leaks. Even after filing the pan flat and ensuring proper torque.

[ICON 1956]

These birds are known to leak from the rear seal of the trans, Here's a video on how to fix.
https://www.youtube.com/watch?v=8tkbKjRsQPw

[Jimntempe]

I made screen caps off your video and put it next to my photo. As you can see, the geometry of your problem linkage is different than mine. I think Rusty has identified the issue, you need to pull the linkages and links and stuff apart and get things reoriented back to "factory". If you look at the arm which has the link to the carburetor connected to it, you can see that yours is starting out at idle rotated too far clockwise. Because of that, when it starts to move, instead of pulling the link backwards it just moves it's end downward. Net result is instead of the overall motion being a backward pulling motion on the link to the carb, it's just a circular motion of the link end from up to down without moving the link very much back.

[1957Birdman]

I ran a 4160 on my car for many years with no problem. There should be no reason to fabricate a different connect throttle connecting rod to make it work. The bell crank bracket does not connect to the manifold as it does on my car. The primary throttle shaft assembly does not look like the original and appears to stick out farther from the carburetor than mine does. Did you get this carburetor from one of the T-Bird parts people and someone that insured that it would fit your car. There are lots of different versions of the 4160 and not all are meant for the Thunderbird. I would check that first and then review things on the bell crank side to be sure things there are as they were when the car left the factory.
Lew Bachman
1957 Colonial White

[Rusty57]

It sure looks like someone modified the original throttle link to fit your application. As 1957Birdman noted there are lots of variations of then throttle arm on a Holley 4160.

I think they first straightened the link and then bent the offset into it. It also appears to be installed backwards which might not be an issue. All the bends in the linkage in this picture are in line between the carb and the throttle arm.