’74 Spider, modified Dual Carb throttle linkage
Here, you can see the engine in my ’74 Spider. It’s a 2000cc with 40/80 cams, a lightened flywheel, electronic ignition, and Dual IDF 40’s.
Here I will detail my customized throttle linkage.
This was one of the more serious, non-previously-documented modifications that was the one huge gap in my overall plan.
All of this would have been impossible without fellow Chi-FLU’ster Max Bassler. Max's help and experience was invaluable, and a long day at his house made short work of the biggest obstacle on this portion of my project.
“The Beast” in Max’s shop
"Part one" is the modified gas pedal. The spring-side gets about 3 inches added, with a socket-ball added on the inboard side. Maintain the spring-hole, that doesn't change.
The original arm & ball “could” be eliminated, but we left it. Also, be careful of the tall upward arm for the manual throttle – it might hit either the firewall, or the back of the carb. We got mine hooked up, and I look forward to once again having “cruise control” in a Fiat!
Below you can see the main piviot. It’s a stock piviot with an additional new rear mount instead of the previous firewall mount (no more linkage binding on acceleration!). I used a surplus front mount, with the same grommet & bushings.
The Piviot arm itself does not need much modification (after cutting it, we realized the original length was ok). The ball on that shorter rear arm had to be reversed onto the other side, but that’s the only mod to the stock piviot.
The little triangle 90-degree mounts had to be cut a bit to fit onto the manifold bolts on the underside of the PBS intake manifold.
Below is the front piviot-arm's linkage to the carb.
This arm was not modified, just a generic adjustable set to the shortest possible length.
This is the rear piviot arm’s linkage. Very short.
A detail of the piviot, looking towards the rear. The ball on that shorter arm had to be reversed onto the other side.
I was tempted to angle one or both of the linkage arms, maybe even adjust the angle between the piviot's arms...and I was worried about "slack" in every joint between the pedal and the carb. But honestly, it works well, and feels just fine.
Notes for future improvements -I may either increase the spring tension a bit, or even lengthen the piviot a tad - as it moves back & forth (front to rear) about an inch, with every stomp of the pedal, when it should only be rotating side-to-side.
Perhaps after getting the rest of the car sorted-out, and driving it a good many miles I may want to tweak it a bit, but seriously, it "feels" 100% the way it should, which I'd been VERY concerned about.