1. What is ment by "amount of vacuum at canister"?

2. how is it determined?

ok your ? and topic are two different things but any way the canister is the charcole canister in the front of the car on the drivers side. if you wanted to check vacume i would suggest checking it there but w/e no difference imo. you will need a guage for vacume to hook up to one of the lines while its running

why are you asking this???? whats the prob with your car

i guess i should have explaned better so hear it goes...

i just purchaced and installed an MSD Streetfire distributer. its an HEI with the coil in cap and a vacuum advance. it comes with a a sheet of instructions and on the back side of that is a graph.

the longitude(up and down) variable is degrees of advance, the latitude(side to side) variable is the number of time you turn out the adjusting screw in the vacuum advance.

based on the amount of degrees you advance your timing (im assuming by using a light and physically turning the distributer) and the amount of turns out you make on the vacuum advance, you end up with a number that is labeled "amount of vacuum at canister"

so i ask again. What is ment by "amount of vacuum at canister".

ill post a pic of this chart in an album in my profile.

it means the amount of vacuum the canister receives isntead of manifold vacuum. What you do is, you tune it so that the canister adds a certain amount of degrees to the full mech. @ cruise and light throttle. Total mech + vac should be @ around 52. Total mech around 36 all in by 2500RP (check w/ light).

If 36 @ 2500RPM you need an additional 16 for light cruise to get to 52. That's where this adjustment comes in. Diff. manifold vac. for different engines. I myself however prefer a fixed non adjustable cap.

I can send you a list of reference numbers. i always set it and then measure manif. vac @ certain RPMs and decide what can I need, they differ in amound of degrees max pulled in and where they start (operating range of vacuum)

Vacuum at your vacuum advance canister should be the same as manifold vacuum.

Both centrifugal advance and vacuum advance are forms of mechanical advance, but should be referred to, and adjusted, separately.

I will refer you to this thread for correct information:
https://www.thirdgen.org/forums/tech...questions.html

You are forgetting about initial advance

Better read this:

http://www.73-87.com/7387garage/drivetrain/hei.htm

http://www.corvette-restoration.com/...ine_Timing.pdf

I know both centrifugal and vac advance are introduced mechanically, that's not the point. The point is to adjust the can separately after setting the centrifugal.
Vac at his can is manifold vacuum (or times, depending on what he chooses) but his can is adjustable, not a fixed unit.

^ This is good information.

I still think that the vacuum advance numbers are too high, unless of course you have a lazy centrifugal curve, and/or and engine that makes very little vacuum ( low DCR ).

That is EXACTLY what I said in my post. So, now please explain to me how I was wrong again?

There's no lazy advance curve, it's a quick one. All centrifugal in by 2500 and then tune the light load/steady cruise to 52 w/ the can, either a selected oen or (not my choice) an adjustable one.

I have all my nonFI cars tuned like that and you say it can't be done. I must have 5 of them that are doing miracle things.