Question on testing vacuum advances

[Larry M.]

I have four vacuum advance units (loose, not mounted in a distributor) that I've been testing with my Mityvac to determine the vacuum at which the arm starts to pull in towards the canister, and the vacuum at which the arm has reached its limit of movement.

I'm basing my results strictly on my visual observation of the vacuum figure when the arm starts to move, and the vacuum figure at which the arm reaches its movement limit.

This seems to me like a rather subjective method of testing. Is that all there is to determining those vacuum points, or is there some more objective measurable method?

Thanks for any info.

Larry

[Leif A.]

Re: Question on testing vacuum advances

That's pretty much it Larry. That's how I check mine before purchasing them over the counter at my local parts store to be sure they're within spec.

[Larry M.]

Re: Question on testing vacuum advances

Leif,

Thanks very much. The method made sense, but almost seemed too simple to be the one to use.

Appreciate your reply.

Larry

[Duke W.]

Re: Question on testing vacuum advances

It's a simple device, so testing function is simple. The start and stop points should be within about 1" Hg of spec. Actual maximum advance has to be tested on the engine or a distributor test machine and should be within about a degree of spec.

Duke