Pictures below show the rear seal arrangement for the MGA Twin Cam engine. (Photos from Mark Wellard in Australia). This resides in the same location as the mechanical scroll seal of the pushrod engines, but the surface of the crankshaft is left smooth and there is a groove in the engine block and bearing cap to accept a rope seal. To the best of my knowledge the rope seal configuration was never used in any other Austin B-series engine, although it was common in other engines of similar vintage.

The "rope" is a braided fabric cord impregnated with graphite powder (or maybe molybdenum disulfide). Cross section of the cord is important to closely match the cross section of the groove so the seal will have a snug fit against the crankshaft. Cord too thin will not make a good seal, while cord too thick will prevent full seating of the bearing cap and cause the crankshaft to bind up.

The main bearings and crankshaft may be test fit first assuring proper free rotation of the crankshaft, then crankshaft removed for fitting of the seal. For installation the seal cord will be pressed into the gland (slot) in the engine block, and the crankshaft can then be seated firmly in the bearing cradles (with bearings in place) to properly compress the seal. The crankshaft is then removed, and the seal cord is trimmed flush with the block using a razor knife. Similarly the cord will be pressed into the gland in the bearing cap, and the bearing cap (with bearing shell in place) will be pressed firmly against the crankshaft to compress the seal. The bearing cap is then lifted free, and the seal cord is trimmed flush with the bearing cap. The crankshaft is then returned to the block and the main bearing cap(s) installed.

Photo on left shows the bearing cap (without bearing) with the sealing rope pressed into place but still protruding a little above the working surface. Photo on right shows the assembly (with bearing) after the parts have been pressed into assembly to fully seat and compress the seal.