Identifying Wear

Lucas PI throttle linkage wear

Considering the throttle rods and swivel posts are made of mild steel and operate without bushes, the system is generally long lived.

The CR single rod linkage wears the most as the single rod takes the load of all 3 throttle spindles and return springs.

Wear in the linkages results in excess play that can affect synchronisation of the butterflies. The metering unit provides a uniform amount of fuel to each cylinder based on manifold pressure. Out of balance throttle butterflies result in uneven mixtures in the cylinders which has a dramatic effect on performance. When wear does occur, it is generally the top and bottom swivels on the throttle rods as shown in the pictures. Worn Butterfly Lever Arm Journal

Sometimes the holes in the throttle spindle arms also wear. Usually by the time this has occurred the brass spindles will be excessively worn and will be letting air by, affecting tick-over. In this instance, the spindles and levers will require replacement.

The throttle linkage system fitted to CP cars has individual linkage rods between the countershaft and each throttle body. This arrangement enables wear in the linkages and butterfly spindles to be adjusted maintaining synchronisation without affecting tickover.

The CR system has a single linkage rod to the front throttle body. The butterfly spindle from the front throttle body is connected to the middle throttle body which is in turn is connected to the rear throttle body. In this set up wear cannot be adjusted out. Play in butterfly spindles is taken up before the rotational force is transferred to the next throttle body. If you try adjusting the play out of the butterfly spindles to maintain synchronisation and driveability you end up with excessively high tickover. If you set it to have good tickover you loose synchronisation.

We can recondition CP and CR throttle bodies with new spindles, linkage rods, lever arms etc. To ensure this is a one off fix and to prevent any future wear, we fit butterfly spindle bearings. Whilst this is a sensible upgrade for CP cars, it is a must for CR cars and really is how they should have been built to start with.

If you prefer to utilise the CP linkage system and are not worried about originality of your CR car, we can also provide CP conversion spindles, new original spec linkage rods, countershafts etc. For more information on the available options, complete the enquiry form here.