Progressive throttle linkage?

[Pentroof]

No, I'm not talking about secondaries. I'm looking for a setup that allows a progressive pull on a Holley setup, in this case, a Sniper setup on a 390 in a 1970 F100.

The trapeze linkage was shot, so I'm currently using a direct rod from the pedal lever. It was too touchy for my daughter, so I added a demon extension lever.

Even with the throttle adjusted to the point that the pedal won't attain full throttle at the throttle body when the pedal hits the floor, the pedal is still too far off the floor at idle. In a car, this wouldn't be a problem because you push "in" on the pedal. In a truck, the angle with your leg is such that you're almost pushing down. It's uncomfortable to set your heel on the floor as it is. My daughter has to almost hang her foot in the air. I think it's dangerous.

I would like to change the linkage such that the overall travel of the pedal was reduced and the first 50% of pedal travel only yields about 25% throttle travel. I looked for about an hour last night and couldn't find a true progressive setup for a Holley. There are many available for standard FI throttle bodies, but I don't see anything for a 4150 style.

I'm not opposed to changing the pedal assembly, if there were something available at that end. It would be nice to get the pedal closer to the floor.

Any suggestions appreciated.

[BattlestarGalactic]

Either need to lengthen the pedal rod(engine compartment side) to pull farther with less travel at the foot or shorten the hole height on the TB arm so it pulls farther with less travel.

All the bump sides I've had, I've always just used a straight rod. That monkey motion, Rube Goldberg set up was always plum wore out and was discarded.

[cammerfe]

Some years ago I was working on a dual throttle-body Holley EFI set-up on Brother Lon's 427 Mustang. At that time I got a rather trick cam-style lever to go on each throttle-body. They were made to be progressive with little actual travel in the first part of the movement so as to remove touchiness. They worked very well; designed to bolt on the lever of the TB.

So such a thing does exist, or at least it did.

KS

[andyf]

The Sniper can be run in progressive mode. You need to change the linkage arm on the throttle body and then check the box in the software to make it progressive and then tell it when the secondaries will open. The secondaries will usually open around 35% or 40% on the TPS.

Having the Sniper run in progressive mode will make it less touchy at low throttle opening. But you'll need to modify the AE tables since the Sniper thinks it needs a lot of AE (pump shot) since it thinks all four barrels are opening at the same time. Progressive linkage on the Sniper is not recommended and is not supported by Holley, but it is possible. I did it on my car and got it working okay but I eventually switched it back to 1:1.

[My427stang]

The old F100 pedals can be a pain, you can usually move the linkage lower on the throttle arm, sometimes takes some thinking, if not, lot's of bell cranks you can adapt out there if you don't want to use the goofy factory design.

I like the idea of a progressive linkage, but as Andy said, EFI is looking at a TPS on one shaft, it'll need tweaking to understand what is happening for the second. If Holley thought of that, very cool.  I am not sure how much that will shorten your overall throw, but if it works let me know, because I am about to buy a kit for mine and that would lean me toward the Sniper

[Pentroof]

Andyf: As my first comment in this thread stated: I'm not talking about the secondary progression. Yes, I have installed a progressive tie bar between the two shafts (like a normal 4150), and I have modified the AE to accommodate the 42% delay as witnessed by the TPS positioning when the secondary starts to open. I think it's lame that Holley makes the progressive secondary an option (selectable within the software) but then say they don't support it.

Back to the regularly scheduled program: I think I may look into adapting a progressive cam for a cable. This is the easiest and cleanest way to get to true progressive (not delayed) action for the primary. They are common on a number of EFI throttle bodies and also on motorcycles and snowmobiles. On a sled, it gives you more control and light thumb pressure for low speed trail riding while still allowing full throttle. Same with a bike: you don't want to have to twist your arm 3/4 of the way around the bar to get full throttle, but you don't want the tip-in to be real twitchy either.

[Pentroof]

As an example of a dramatic version, this came from Only944.com. It's the type of cam I'm looking to adapt to the throttle shaft on my Sniper (primary). You can see how the pedal to throttle ratio changes dramatically as the radius from the pivot to the cable groove around the perimeter changes.
This one is a bit dramatic and more of a bimodal progression with a step change, but many have more of a cam profile.

This one looks too large to fit under an air cleaner base. There should be one out there I can adapt. If not, I can design one and print it. I have access to a metal 3D printer.


Source: https://www.only944.com/instructions/trcinstructions/



On edit:
Getting closer:
https://www.weberperformance.com.au/product_info.php?products_id=836

[Pentroof]

Mother load!

https://www.efihardware.com/products/2246/Bell-Crank-with-Adjustable-Cable-Pulley-and-Return-Spring-Tensioner

[BattlestarGalactic]

Interesting.  Never realized that motorcycles had that kind of progressive linkage, but totally understand now.  The spiral radius changes and thus the ratio.

[cammerfe]

The references just above, although NOT the item I was speaking of, are just the sort of thing I made use of. At that time the source was local to the Detroit area. The guy was a retired GM engineer, although I didn't hold it against him.

KS