That's true of ANY mechanical gauges. The mercury/other gauges are different.They will work, however, you should connect all 4 at once to a vacuum source, and verify they all read the same. Make any notes of differences, pick one as reference and mark the others with the discrepancy. In other words, you are verifying the calibration and will take any discrepancies into account when doing your sync.
I have used the mechanical gauges several time, and managed to get very stable readings by adjusting the restrictors. Super easy to do.I was going to go this route with these gauge types. I read somewhere that the needle bounces because the vacuum is pulsing, and hard to get a measurement. Has anyone tried to use these type of gauges and has feedback. The fluid or mercury in the columns seems to buffer that effect, however I don`t always believe whats on the internet
after an engine has been broken in / run in ( there are many POVs to how that process works effectively )
As I said above I have a set of 6 of these I use to sync the carbs on my cbx’s, they‘ve worked well for over 20yrs. to set them up you have to connect them all to a common vacuum source as Ray said above. If they read differently unscrew the lense off of them and use the silver screw on the face to adjust their reading until they’re all the same.
I've always disagreed with this statement. For no other reason I guess that there is (and always has been) a specific number given in the FSM to set the vacuum to.I sync the gauges before each use, I hook them all up to my MityVac hand vacuum pump through a multi tee I made up so they all see the same vacuum. The actual number is irrelevant just so they all read the same, once they are the same then I sync my carbs/throttle bodies. Setting them up usually is pretty easy & quick, depending on the day.