stvaughn

On a past thread it was mentioned that a Mityvac could be use to test the vacuum canister but no mention of the procedure involved. Please explain.

Steve

LB66383

You can use the Mityvac to apply vacuum while you use your fingers to feel when the canister's arm starts to move, and watch the gauge. From that you can get the vacuum readings for when the canister starts to activate and when it is all in. You want the "all in" value to be 2 or 3 inches Hg below your engine's vacuum reading at hot idle.

For a lot more info, get a copy of Lar's papers on vacuum advance theory and practice.

stvaughn

Thanks, I do have Lar's papers. Just have to get a Mityvac.

Steve

dugsgms74

Just a little side note. The gauges on mityvac units are notoriously inaccurate. This is OK if you just use it for seeing if the unit works but if you want to test it for "Hg opening and "Hg per degrees of advance a better way is to hook up a large face dedicated vacuum gauge with a vacuum "t" while testing the unit. That along with a quality "dial back" timing can test the vacuum advance unit very accurately.

stvaughn

Thanks, I do have a vac gauge so I can do as you suggested and verify the accuracy of my Mityvac at the same time.