Installing the throttle.

Today I installed the throttle pedal and the cable to actuate the throttle body.

The throttle pedal is a simple spoon throttle like this. I bolted it to the firewall shelf directly above the footwell. This required drilling two holes to bolt the bracket to and cutting a slot for the throttle lever. I cut the slot by drilling holes at each end and then used a hand nibbler to finish the slot.

Throttle pedal attachment from belowThrottle pedal attachment from above

For the throttle cable I bought a universal throttle cable from the local Checker (Spectre Universal Cable 2431). The end of the cable had a swaged fitting that was not compatible with the throttle linkage on the L67. Nothing that a drill couldn’t handle though! I drilled a hole through the back of the throttle bell-crank and fed the cable up through it and bolted the cable housing to the existing cable bracket on the throttle body.

Drill the throttle brack for a different cable end

The cable moves 4.5cm from wide open throttle to idle. I placed my pedal so that at idle it was just slightly above the brake pedal. Whether this will be acceptable or not will be seen later. I swung the pedal from idle to where I wanted full throttle and used an angle protractor to determine that the throttle was swinging through about 37 degrees. Using a little high school trigonometry indicated that I needed a hole in the throttle lever 7cm from the center of rotation for the lever (for the interested, the formula is r=\frac{d}{2\sin \theta/2} where d is the distance the throttle cable needs to move, \theta is the angle the pedal moves through and r is the distance from the axis of the throttle to the center of the hole for the throttle cable). This gives a nice long travel for the gas pedal, which I feel is very important in a car with this power to weight ratio. I drilled another hole in the throttle lever at the calculated distance and fitted the throttle to the shelf again.

I then fabricated a sheet metal bracket to position the end of the cable housing at the proper distance to the throttle lever. This distance depends on the fittings you are using at the throttle end of the cable.

dscf1711-small.jpgdscf1713-small.jpgdscf1714-small.jpg

Everything fits well and works as calculated. But I am not happy with the “smoothness” of the throttle operation. I can definitely feel that there is a cable being used and there is a lot of resistance due to the “S” turn the cable housing has to make to get from the throttle body to the throttle lever. I have lubed up the housing, but it may need an additional spring to help the return action.

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3 Responses to Installing the throttle.

  1. Jerry Vela says:

    What Up ?I roll in a clean 72 El Camino/350/all stock.My throttle cable snapped!Lucky I was parked.What do u suggest?Junk yard?/or new?.I have a universal Spectre throttle cable/p#2431,in my garage,shood i uz it?…Please Help Me!..El Caminos Rule!

  2. Jerry Vela says:

    Whats ur thouht on Pozi?

  3. enderw88 says:

    As far as your throttle cable goes, unless you really know what you are doing use a NEW OEM part for anything safety/reliability critical. Throttle cables for GM cars shouldn’t be hard or expensive to come by new.

    As far as limited slip rear ends there are several type, one of which goes by the brand name “Positraction”. It is a clutch plate type that limits the slip on one side by engaging clutch packs. These tend to wear out if used in racing conditions. If you are road racing stay away from these. If you are drag racing they can be fine, but be ready to rebuild them each season if you want them to keep up to snuff. Another type of limited slip is a complicated geared mechanism that transfers torque without any friction material being rubbed away. The most famous brand of this type is called “Torsen” but probably isn’t available for your car. I used a Detroit Tru Trac which is available for most American rear ends, check of Speedway Motors or Jeg’s. It is the best solution for road racing. Yet another design used a racheting lock pawl to lock up the differential solid when it senses slip. These are great for truck or drag racing, but you don’t want to be in a corner when the differential locks up.

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