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I bought these about 1980 and they've worked pretty good for me over the years

yes a fantastic bike all original very low miles

I have to go with the manometer, NOT the gauges. I have found with gauges, they might also read the same at, say 17 in/by. But, everywhere else, all over the map, even with the damping valves in place. That is just the nature of them.

Now, if there is ONE pool of a liquid media to pull from, with tube and hose lengths the same, the read is as it is, totally accurate, not varied by gauges that will never read the same.

That said, I built my own mercury manometer long ago, 8 tubes, to use on a Hilborn stack injected drag car I ran, not hard to build.

I used clear plastic tubing and a plastic reservoir, glued together, mounted on a long section of wood trim, spray painted white, with black level lines. Cost was less than 10 bucks American. Largest cost item was the mercury itself.

I also read all 6 vacuum levels, as differences can tell me if there is an intake valve clearance that needs attention.

Thanks for the reply

stocktoy, one thing that would make those two manometers work better for the 6, is to link the two mercury pools at the bottom of the stix together. If the two manometers have the slightest difference in mercury volume, one manometer will read a different vacuum level. A common pool will pull exactly what differences there are, more accurate, but, you are on the right path so far.

When I do mine, I always read all 6 carb bores, not only 3, as some do.

usakz1300 wrote: stocktoy, one thing that would make those two manometers work better for the 6, is to link the two mercury pools at the bottom of the stix together. If the two manometers have the slightest difference in mercury volume, one manometer will read a different vacuum level. A common pool will pull exactly what differences there are, more accurate, but, you are on the right path so far.

When I do mine, I always read all 6 carb bores, not only 3, as some do.

That's true and I never thought of it way back when I have to admit.