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vacuum gauges to sync carbs?

  • Thread starter Thread starter retired optec
  • Start date Start date
R

retired optec

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Has anyone ever used vacuum gauges to sync their carbs. Will these work as good as mercury gauges?
 
I've have a set that i use...seems to work fine for me
 
retired optec said:
Has anyone ever used vacuum gauges to sync their carbs. Will these work as good as mercury gauges?
Click to expand...
Yes, they can work, but "as good as mercury gauges"? Not sure about that. 8-[

Mercury sticks require NO calibration. Because of that, they are THE standard for measuring vacuum. It makes no difference whether your column of mercury is 1/16" or 1/4" in diameter, a given level of vacuum will suck the mercury to the same height.

Aneroid gauges (or analog gauges) tend to need a bit of calibration. The best thing to do is to make a manifold that you can attach all four gauges to at the same time. Connect them to a vacuum source. It can be one cylinder of a running motorcycle, a vacuum pump or whatever, but they all need to read the same vacuum level at the same time. Compare the readings, there is usually an adjustment to make them all the same.

NOW you are ready to connect them to the individual intake runners to do the sync.

With many gauges, the needles are very light weight, therefore very sensitive to pulses. You will need restrictors in the vacuum tubes to minimize these pulses to a tolerable level. Yes, mercury sticks pulse, too, but I kinda like that, it shows me just what is happening.

So, if you don't mind doing the adjustment check every so often and you don't mind not having any mercury to spill, aneroid gauges are a decent alternative.


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Don't know about bests etc... must be personal choice.....

Mercury ones need to be keep upright and if you get it wrong you couls suck mercury into the engine?????

Vacuum need recalibrating each time.

Suzuki mad
 
Suzuki mad said:
Mercury ones need to be keep upright and if you get it wrong you couls suck mercury into the engine?????
Click to expand...
True, the 'sticks' need to remain at an angle above horizontal to prevent the escape of mercury, but I have never seen a vacuum high enough to suck the mercury into the engine. Maybe eventually, as I have only had them for 28 years, so far. 8-[


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What's wrong with a single gauge hooked up to a four valve manifold such as an aquarium air distributor? No calibration needed.
 
Jaguarjoe said:
What's wrong with a single gauge hooked up to a four valve manifold such as an aquarium air distributor? No calibration needed.
Click to expand...

In theory and with patience it would probably work. But it seems that the 4 guages would be much easier. At least on VM carbs, adjusting one carb affects the others. It could be a real pain going back and forth all the time.
 
Jaguarjoe said:
What's wrong with a single gauge hooked up to a four valve manifold such as an aquarium air distributor? No calibration needed.
Click to expand...
True, no calibration needed, but it would be a real pain in the ...
The calibration is not hard, it's just something that needs to be done to aneroid gauges that does not have to happen with mercury columns.

If you were to see how the readings of the other cylinders are affected when you change just one adjustment, you would clearly understand why it's important to see them all at once.

I have not yet used a digital set, but I understand they work well and are easy to use. Personally, I find it easier to look across a row of four bouncing columns of mercury and compare heights than it is to compare the angles of four bouncing needles.


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I read that vacuum gages work, but that high-quality versions are required to have the needed sensitivity and reliability. No personal experience, but it sounds reasonable.
 
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