Distributor Body Clamp – Easy To Make – Easy To Adjust The Ignition Timing.

The small things on an engine that require adjustment can sometimes be the most irritating chores to do. Most twin cam owners would readily agree that, that certainly applies to the original Lucas distributor body clamp on the Ford Lotus twin cam engine, tucked away under the twin Weber DCOE Carbs.

The holding and adjustment clamp supplied with the stock distributor can be become a total pain in the ass when it becomes worn, and often times even when loosened, the clamp still wont allow free & easy clockwise – anticlockwise adjustment of the distributor body. you don’t need that when making adjustments.

Many, many yeas ago during an engine rebuild, this modification was earmarked for early attention, but a little bit of thought was required to come up with an easy to make, and easy to adjust solution.

The solution was to machine the lower part of the dist body where the original clamp was situated, then a special mild steel clamp ring was machined so that it was a neat fit under the new machined shoulder…. you will need to refer to the photos below to understand what is being done here.

This special clamp modification requires that the distributor is removed from the engine and totally dismantled for machining of the body where the ring is going to locate as shown in the photograph below.

The machined metal ring is securely clamped to the distributor body with a custom made threaded sleeve incorporating a 3/16″ cap screw, the threaded ferrule is brazed to the ring as shown, a small section is then cut out and removed from the ring to convert it into a clamp ring. The ring is required to be securely clamped onto the distributor body because you don’t want it to move and give incorrect ignition timing.

Side of dist body where main clamp does it’s work.

Next is the main clamp plate which holds the dist body in the set position for correct ignition timing, the clamp stud is undone until the dist body can be rotated either way, there should be no drag or hesitation when the dist is moved.

What you are looking at now is the side where the main holding plate is clamped down onto the ring attached to the distributor body, the next shot will show the holding plate in place. The clamp plate is machined from a small piece of 1/4″ thick flat mild steel plate, the quadrant shape is cut from the plate after machining to size, the bolt hole is best if it is made oval to allow free movement of the bolt and the plate.

The reverse side of the clamp plate

As mentioned above, the holding plate is machined and cut from a piece of 1/4″ mild steel plate and held with the standard 1/4″ UNC stud as used with original clamp.

To make the holding plate requires machining in the lathe, begin with a square piece of mild steel, cross mark and centre pop, then mount the plate in the four jaw chuck, and dial up true, begin boring and machining until you arrive at the smallest ID, then machine the groove to fit the clamp ring shoulder dia which is a little larger in diameter, we are unable to provide measurements as this mod was done several decades ago, but if you have your old dizzy and other bits, you will be able to work it all out.

This special mod is well worth doing as it makes the fine adjustment for accurate ignition timing so easy to achieve, no more struggling with an old stuffed dist clamp that does not want to let go, or also does not want to tighten up.
Good luck.