The Nut Behind the Wheel: Fall 1999

My best buddy Bob, who never listens to my timely, quality Healey advice, is moving ever so slowly on his BJ8 restoration. While he is making some progress, he’s got some problems with sequencing and priorities. Like he hasn’t got any interior in the car yet and he’s concerned about getting full throttle.

This tells you a little about Bob. It’s not like I didn’t tell him to adjust his throttle linkage before he put the engine in the car. Why is this important? Because it is almost, but not quite, impossible to adjust the chassis part of the linkage correctly with the engine and transmission in the way of using a wrench on the most important of the throttle linkage pinch boll connections. And now, it’s all true, in test running his car in the garage, his SU carbs can’t open all the way because the linkage needs adjustment. That’s why there are those days when “throttle” accurately describes what ought to be done with him! So…for him and you, here’s how.

His following instructions are for six cylinder cars only. While original shop manuals do not show a diagram nor explain how to adjust your throttle linkage, the vintage Haynes workshop manual docs. Unfortunately, the written information doesn’t always correspond to the illustrations, and the second half of the information is for the HD6 (100-Six and 3000 Mk I) set-up only. However, this first part pertains to all six cylinder cars, as it describes how to set the linkage that is attached to the chassis. I’ll start with a little theory.

As the carb’s throttle shaft rotates on opening, on HD-style carbs, a pinned tang on the throttle shaft will rotate and, at full throttle, will contact a protruding portion of the carb body. For the tri-carb model, a positive stop is provided against the heatshield. What you need to do is to adjust the linkage to allow the toe board to act as a positive stop for the accelerator pedal when the throttles are fully open. If the toe board doesn’t stop the throttle from opening further, you might risk breaking off the tang on the linkage at the carburetor in your exuberance to go faster! If your foot hits the floor before the throttles are fully open, then you will be missing some of the excitement of driving a big Healey!

To adjust the chassis linkage, first slacken the pinch bolt on the pedal box throttle pedal lever inside the engine bay. This is where those of us with left-hand drive cars will wish we had done this before the engine was installed! There’s plenty of room on the right-hand drive linkage to get to that pinch bolt, since the accelerator pedal is on the other side of the car.

With the pinch bolt just loose enough for the shaft through the pedal box to turn, put a 2 1/2″ thick wooden block between the pedal and the toe board and push the pedal down so it rests on and retains the block on the toe board. Be sure you have all your flooring pieces in place—tar paper, jute underlayment, carpet, and doormat, or whatever you are using this week. Why lose up to an inch of travel once you’ve installed your interior?

Now adjust the pedal box lever relative to the pedal cross-shaft lever to obtain a clearance of 1/16″ between the cross-shaft relay lever and the body flange under the scuttle. Tighten the pedal box throttle pedal lever pinch bolt. Note that early cars have in adjustable cross-shaft relay lever complete with pinch bolt. Don’t confuse the two. Be sure the cross-shaft relay lever’s pinch bolt is tight before making this adjustment. For later cars (BJ7/BJ8), this cross-shaft relay lever is brazed to the cross-shaft and isn’t adjustable, nor does it need to be. Now you all can run out to your cars and visually see if this is true or not. Is that 1/16″ of clearance there, or does the cross-shaft lever contact the body with the throttles at rest? I’m willing to bet that the majority of cars will have their cross-shaft lever contacting the chassis when the linkage is at rest instead of having that little bit of clearance. This takes care of the chassis part of the throttle linkage, the part you want to do before you put the engine into your fresh restoration. In the next issue of Moss Motoring, I’ll take up the adjustment of the engine portion of the throttle linkage.

—Ron Phillips

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