Picking up the conversation from the parallel Saloon thread. What a/c kit did you install? How many times have you suffered a 1500-mile belt failure? Do you suspect any cause other than the one-belt arrangement?
I’m using a Classic Auto/RetroAir kit, but modified as discussed above.
For my system, the shop fabricated a two-groove crankshaft pulley. One belt runs around the outer groove of the crankshaft pulley and the a/c compressor. The other belt runs around the inner groove of the crankshaft pulley, the alternator, and the water pump. There is no idler.
If you look up the thread, you’ll see a few photos of my system in its initial stage of installation. There are several geometrical constraints that need to be satisfied: the alternator needs to clear the steering shaft; the compressor can’t be so high that the bonnet won’t close (or, worse, dent); and, the plane of belt number 1 has to be different from and parallel to the plane of belt number 2.
Although we share an engine, some of the other differences between an E-type and a Mark IX may factor in: bonnet shape and height, steering shaft location and angle, power steering (y/n), frame rails, etc. I think that it is worth attempting on your car, but your fettling may vary (YFMV).
Bob
@REBUILD61OTS I wonder if a dual pulley on the water pump would work better or worse than a dual pulley on the crank. I hadn’t thought of that before. I don’t think that the location of the dual-groove pulley would affect any of the geometrical constraints. The belt distance from water pump to a/c compressor is shorter than from the crankshaft pulley to the compressor, if that matters. On the other hand, the water pump pulley is “secondary” in that it is driven by the crank pulley (the “primary”) via a belt. Is there any issue with the compressor pulley being in a “tertiary” position?