Pushrod length

If your motor is apart why not set up cam and rocker and measure the required length? This will either give you a close approximation of one of your two dimensions or prove the fault and subsequently improve the performance, when the correct lengths are installed.

Jon

Your measurements are closest to the earlier 650, 8.21" and 7.36". Yours should be 1/10" shorter, 8.11" and 7.26" for post '66 models, including 650SS, Mercury, Atlas and pre-Combat 750 Commando, because the valves were 1/10" longer than previously.

Ian C.

The change of pushrod and valve lengths officially happened after engine 125871. This was right at the end of 1967 when Commando components started to be used in all the remaining Dominator models. This included the Mercury and later 750 Off-road Hybrids.

This change was apparently done to enable a better rocker angle. There is a good chance that owners of earlier Dominator models also used the later parts, on their engines, during major servicing. The attachment shows the Factory specifications but these rarely match what emerges from engines. I suspect that rods shorten during service but this is not noticed due to valve seat  recession.

I suspect a typo in these specifications in that where it states 650, Atlas & Mercury 1966 on this should reallt read 1967 on. Engine 125871 was manufactured at the end of that year.

Phil. If they were indeed changed from 125871, that chart is a little misleading, as it says 1966 on. 125871 appears to be in the 1968 numbering sequence, although, as you say, produced in late '67 for the '68 model year. Certainly not in '66.

I wouldn't be too hasty about discarding your existing pushrods, William, without first checking your valve lengths. If they are the original barrel-shaped hollow alloy ones with steel ends, they are desirable, being very light. They are no longer made, so any which you buy will be heavier. Even if they need shortening, I believe it is possible to remove the steel ends, shorten the rods, and press the ends back on. Cheaper, too.....!

Ian C.