Buy one of these, and be done with it...
https://tinyurl.com/yb5fdwo3
No better tool on the market...
Now that's interesting. I don't know why, but I have a hard time mentally getting over that it's electronic -- mechanical gauges/rods/mercury just makes more sense to me... I'm sure it's good, but I mean, for just about the same price you can get a morgan carbtune with 4 inputs, rather than 2.
Allow me to explain, and simplify its manner of function.
first off, you don't need 4 circuits... all carb synches are an adjustment between "pairs" of carbs, or throttle bodies...
C10 for example has 3 adjust screws... you synch #1 & #2, then #3 & #4, then the pairs on both banks, #2 & #3... for final adjust.
the electronic portion of the TwinMax, is a simple yet very adjustable and highly precise electronic "balance" needle, that does the 'A to B' comparison. it is "zeroed" manually prior to beginning, so there is no possibility of inequality between "A and B".

you can adjust the sensitivity if so desired, to a point where you can see the reaction points of the intake valves working on the tract.. that's overkill, but in all earnest, due to the design does show extreme precision when syncing.
My personal experience, and feelings over 45 years of doing vacuum adjustments, have had me experiment with all manners of tools, and when you have 4 circuits, you have 4x the opportunity for differences in precision, of manufacture that come into play.. 4 different tubes, 4 different slugs of metal being sucked upon, 4 different states of wear on each physical part doing the work to "show" what the vacuum is.. same as 4 individual vac gauges... are they all Identical? no.
The Morgan tool works fine, but its kind of a pain to transport. I have also played with it, and found on occasion, when you get all 4 sources "perfect", and then switch the hoses around to check the tool... readings may differ..

Same as I found with Vacuum "dial gauges"..

Mind you, I have owned and used many different products, and in the end, sold them all off, and keep my TwinMax, and my original set of Mercury filled Genuine Kawasaki 4 tube metering stick. Only reason I keep that tool, besides its cool, original, and 40 years old, is the fact it is a precision glass tube device, that allows me to do actual "millimeter of mercury" measurements, when desired.
The actual glass tubes have an inside diameter of 1mm (.039") and are almost 36" long.. tough tool to protect for 40 years...

Lots of folks make their own versions of Manometers, using ATF and plastic tubing... and they kinda work also. but a 1/4" i.d. plastic hose is pretty crude..... in comparison.
