Anybody test a vacuum cut-out? ’57 Lark

[billy-j]

I have taken them apart and changed the diaphragm and cleaned the contacts.You can just put on a piece of vacuum hose and suck on it and check it with a ohm meter for operation. One other pointer they are specific to the motor year so before you mix and match do your homework. The spring inside of them is matched for the specific motor and sometimes varies from year to year so check the springs part number. The part number for the complete cutout should be stamped on the aluminum housing and from this you can check if it has the correct spring you need.

[mas]

Well, I just bench tested my unit with my Mityvac and got about 4 inches of mercury. On my gauge, pressure is shown in PSI and vacuum shown in inches of mercury. I went to an internet site to convert to psi and got two possible answers:

So which psi is it…2.0 ish or 12.7 ish?

Mas

[mas]

I guess almost 13 psi is an awful lot…so it probably is the 2.0 value??

Mas

[fisherman6]

Simply stated 4 inches of HS is equal to 1.96 psi.

That is PSIG or Pounds per Square Inch Gauge. The -12.73 psi is PSIA or Pounds per Square Inch Absolute. The ‘Absolute’ value is realtive atmospheric pressure which is roughly 14.7 psi at sea level. The 1.96 – 14.7 gives -12.73 psi relative to atmospheric pressure. Hope that helps.

-Ben

OldJohnnyRude on YouTube

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