Packard Forum Index » Project Blogs

Actually, I just found some pictures online, and I now understand the orientation.

The linkage travels behind the head/block.

Yeah, that won't be an option for me. So it looks like a cable option is really my only way forward.

On my '54, the pedal has a rod that travels up the firewall first to a bracket that then travels over the engine. So I was expecting something similar.

McMaster has a decent selection of push-pull cables and end fittings for them. V8s do not use that flexible rubber isolated firewall vertical arm to rod piece the earlier models used so you might be able to use something from a 55-6 for the pedal to cable linkage and transition.

Just for reference, this is what the current "linkage" look like on the SU Carbs.

Where most of the Packard carbs had a front-back throttle action on the carbs, the SU carbs have a side-side action. So the movement is 90 degrees on a different plane vs the Packard default.

Right now, the peddle is attached to a rod that is linked to a piece of pencil rod that is bent in a large u-shape that is horizontal to the ground.

So when the pedal is pushed, both legs of the "U" bend towards the ground. The carb side of the U is attached with baling wire to the lever on the carb(s) shaft and rotates downward when the pedal is pressed. (see picture)

But besides being a bit Rube-Goldberg, the geometry isn't correct. So very little peddle action is needed to go from idle to wide-open throttle, and this occurs way before the peddle bottoms out.

Also, with the "U" pivot being attached where the transmission mates to the engine, it's MM away from contact with the floorboard.

All and all, it just needs to be re-engineered, and the only way I can think of is to go with some type of universal throttle cable setup.

Attach file:

---

  ThrottleLinkage.jpg (212.63 KB)

I imagine I would need some kind of teeter-totter or angle bracket arrangement to allow me to change directions 180 degrees and also, based on the point of rotation on that "teeter", that could be used to translate the range of motion from the pedal throw to the carb throw.

Here is a bracket some other guy worked up for SU carbs, but he has the "teeter" in place for reference. While not the same, the idea is roughly the same.

https://www.youtube.com/watch?v=6AZ7sxRR6oU&list=WL&index=1

If you went with cable, you could use something like the V8 accelerator piece to pull the cable. Make a cable support to hold the cable so as to come in from the bottom if you used the accelerator side and cut off the vertical end or mount it out in front and use the vertical linkage side cut to length. Attach the cable anywhere along the red line so as to get the proper pull for the carbs. Depending on how the cable would need to mount at the carbs would determine the other mounting bracket and cable position. You could mount the firewall piece higher and make a rod to length from the bottom accelerator pivot if you wanted a cable to come in from the bottom accelerator side as compactly as possible and go across the top of engine sort of following the new wire loom.

If you wanted to go with a solid rod what about using engine mounted brackets such as the V8s used at the back of the heads to hold the Ultra throttle linkage crossover rod. You could custom make brackets to locate the crossover rod in line with the needed carb location as the guy was doing in the video. Custom make a rod to length so as to connect the upper firewall accelerator piece to that cross rod.

Attach file:

---

  linkage.jpg (80.61 KB)

Howards, thats helpful, where is that diagram from?

Not seeing it in the 55/56 part plates.

55-6 parts, plate 19A and 19B. Ultra cross pieces are on 19B.

"Bob, thanks, that's helpful. Do you have a picture of it on the car with the motor in place?"

My camera does not have a time leap feature that allows me to shoot pictures from next spring!

No worries Bob. I figured that part out!


Howard,

I need to look at the firewall and ensure there is room where the pedal rod comes through.

If so, I have to see if I can track down a used 55/56 pedal/throttle assembly from a scrap/parts car.

Kev, was going to send you a picture of the linkage, but you’re correct, it’s very low down.

My car has an R-1 radiator cap, not an R-2. Not sure what the difference is.