Before being replaced by the April 1, 1968, arrival of the 428 CJ, the mighty NASCAR-inspired 427 gave one last gasp in detuned form. Identified by the letter W in the fifth spot of the VIN, this early 1968 edition was the only 427 with hydraulic lifters, an iron intake manifold, a single point distributor, a smog pump (Ford’s Thermactor system), an automatic transmission (the four-speed was not available with the 427), and optional air conditioning. It was probably a case of “building out” soon-to-be obsolete 427 inventory. The W-code 427 and 428 CJ shared just about everything except main bearing caps and bore/stroke dimensions. Common to both were vital details such as camshafts, intake manifolds, valve and port sizes, and compression ratios.
VERY IMPORTANT Note: Elastomer coupling flange is normally cut down and Needs to be mounted on a ridgid Drive/Starter plate on the dyno input shaft. (Do NOT use a flex plate.. Why?). You need to make a spacer (shown in Red) with enough thickness to Crush, or Pre-Load, the rubber on the open back-side to about 1/8". This is needed to keep the rubber in place without shifting (actually best to pilot the splined shaft). Use only a splined driveshaft and Certainly do not put a U-joint or CV joint on the rubber coupling. (Why?). Best to use a light weight shaft splined at both ends, like those used in Sprints and Midgets. Do not use a large, heavy shaft (Why?). You just can't ignore the Physics and why things fail.
SPECIAL NOTE. - GH6 hubs prior to 1952 had the adjusting cone on the dynamo side. This cone is extended to pass through the armature body and is flatted at the outer end to take (K428) notched adjuster washer, by means of which the cone may be turned. Dismantling instructions from 1 to 5 remain exactly the same as for the current model. For paragraph 6 read 'Unscrew the dynamo-side cone and lift the ball cage out of the hub shell. The spindle may now be pulled out from the other side, together with the fixed cone.' All further comments apply equally to all GH6 hubs.