I thought there was something different somewhere Terry, although I may be thinking of 6cyl. Didn't one of them have more timing marks or something? I don't have any newer stuff here to measure. I only kept a few good HT-G, one HQ-early HJ and the one later HJ-HZ one. I scrapped anything with any hint of corrosion or those from about 1980 onwards.
Yeah the Holden 6-cyl timing covers changed 3 times. For EH to HG the long mark was the 5 degree initial timing mark. This was very confusing, many thought that it was the zero timing mark. Each mark was at 2 degree intervals. i.e. 1, 3, 5 & 7 BTDC.
For HQ to mid-1981 this was remedied with a new tag showing zero & then 2, 4, 6, 8 etc. The mark on the balancer was unchanged.
Then, about a year after Blue motors were introduced a new 12 degree tag came in. This time though the mark on the balancer was moved.
It makes it very interesting trying to tune motors made out of bits & pieces, not to mention balancers where the outer ring has moved, making the timing marks completely useless.
Dr Terry