Vacuum pressure on the 170

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Bock120

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Going to check vacuum pressure on my '63 valiant. what should the pressure be?
 
Your wording is a little confusing....


Pressure is the opposite of vacuum...

Vacuum is negative pressure.


Are you referring to intake manifold vacuum? I would say you should expect 17" hg at idle on a used engine give or take....
 
Maybe he means compression? I just love these guessing games.
 
don't forget to stop the muffler bearings from spinning while doing this...
 
You got me, i was talking about vacuum on the manifold side. I have 18" hg, that is with the muffler bearings not spinning, I have around 10" hg on the timing side. The hose looks reasonable, haven't checked it really well, but what else should i check for problems.
 
Bock120 said:
You got me, i was talking about vacuum on the manifold side. I have 18" hg, that is with the muffler bearings not spinning, I have around 10" hg on the timing side. The hose looks reasonable, haven't checked it really well, but what else should i check for problems.
Click to expand...

If it's not the blinker fluid then I'm stumped! Others more well-versed than I will surely chime in.
 
Expressing "vacuum" using the term "pressure" is completely legitimate. No different than the many ways of expressing the two in terms of different measurement standards, whether "pounds per square inch," or inches of orange juice.

In fact, in a different life, I used one of these................

pressure-gauge.jpg


Which is a Bacharach brand oil filled manometer. The thing is, while it is marked and calibrated in "inches of water" that is NOT what is IN it. So it actually does not MEASURE "inches of water," because the OIL that is used is not actually responding to the same height. In other words, if you would substitute an "inch ruler" for the calibrated scale, the instrument would read incorrectly

The point?

You COULD build yourself an instrument that reads in "millimeters of sludge." Or in "feet of 3-in-1 oil" It just so happens that water and mercury are two standards that we "use a lot."
 
67Dart273 said:
Expressing "vacuum" using the term "pressure" is completely legitimate. No different than the many ways of expressing the two in terms of different measurement standards, whether "pounds per square inch," or inches of orange juice.

In fact, in a different life, I used one of these................



Which is a Bacharach brand oil filled manometer. The thing is, while it is marked and calibrated in "inches of water" that is NOT what is IN it. So it actually does not MEASURE "inches of water," because the OIL that is used is not actually responding to the same height. In other words, if you would substitute an "inch ruler" for the calibrated scale, the instrument would read incorrectly

The point?

You COULD build yourself an instrument that reads in "millimeters of sludge." Or in "feet of 3-in-1 oil" It just so happens that water and mercury are two standards that we "use a lot."
Click to expand...

Isn't that a ***** pump vacuum guage? :D
 
thanks guys appreciate the useful information. I'll remember to be sure to use the correct language when asking for help.
 
Bock120 said:
thanks guys appreciate the useful information. I'll remember to be sure to use the correct language when asking for help.
Click to expand...

My point is you DID use the correct term. Aircraft engine manifold "vacuum" is expressed in pressure, whether under vacuum, or supercharged under pressure

13186d1309671613-aircraft-instruments-sale-manifold-pressure-gauge.jpg


At least some of these measure "absolute" manifold pressure, meaning, when the engine is stopped, and the manifold is at atmospheric pressure, the guage will read barometric pressure instead of zero like an automotive vacuum gauge does.

Pressure is pressure. It can be "negative" that is lower than absolute atmospheric, or "positive" like in a tire, higher than atmospheric
 
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