A lot of older cars used throttle linkages instead of throttle cables. My 1971 Datsun 240Z was one of them. Linkage systems are usually quite robust and hold up to decades of abuse. Unfortunately in the 196os and ’70s, they started using plastic pieces, usually the end caps, that sometimes break down, especially when frequently adjusted. And as you can imagine, these little plastic pieces are no longer available over the parts counter, so the only spares you can find is stuff left over from the junkyard. As you can see from the first picture, some linkage systems look like something out of the game “Mouse trap”. I removed this one from my Z race car this week; it has six main components, with a dozen more smaller pieces.
So why did engineers use linkages instead of cables? I’m not sure if throttle cables broke more often in the early days, or if linkages just looked cooler, but a simple cable sure makes things cleaner and easier under the hood of my race car. I had to fabricate a plate to anchor the cable sleeve to since the hole in the firewall for the linkage was larger than the cable sleeve and retaining nut. I attached the cable to the end of the throttle pedal with a nice clevis pin that was part of the Lokar Universal Throttle Cable kit.
Now you need two more pieces to complete the setup. A cable standoff bracket is required to anchor the other end of the cable sleeve. Fortunately I had a part that was easily modified into this bracket, however just about any piece of steel could be made into one. Then you need an arm to attach the cable end assembly to the throttle shaft. The cast aluminum one shown here is a piece made specifically for this application. A little bit of fitting and adjusting, and I’ve got a much cleaner, trouble free throttle system for under $50.
Another advantage of a throttle cable system over linkages is the increase in throttle control that it can offer. By its nature, a multi-link system will eventually have slop in it as each of its many components wear out. Along with the extra play in the system, a notchy feel can occur with this wear. Another problem with a linkage system is that the engine is rigidly connected to the firewall through the linkage mounts. So as the engine rotates within the chassis due to hard acceleration or hard cornering, the throttle position actually changes without driver input. This effect is small, but measurable, and a throttle cable eliminates it entirely. If your racing class allows it, and you can handle the vibration, another solution to this problem would be the use of solid motor mounts.