Vacuum advance cannister on MSD ???
Thread Starter
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Vacuum advance cannister on MSD ???
I've been going over the timing on the vette today. It appears my vac adv canister is dead. Its a B26 that should add 16 degrees of advance.
I pulled the cap & rotor. The first thing I noticed was it took more force than I thought to push turn the "dial" on this MSD unit. It is spring loaded and turns in the counterclockwise direction, which I guess makes sense to add advance.
I hooked my mighy vac hand pump on the cannister and pumped it up to 17 HGs and it didn't move. Also, I couldn't advance it by hand either at that point.
My car pulls about 16 to 18 HGs at idle. My questions are...
1) I presume this can is shot, right?
2) Should I stick with this B26 can?
3) Should there be that much load against the vacuum advance inside the distributor?
I pulled the cap & rotor. The first thing I noticed was it took more force than I thought to push turn the "dial" on this MSD unit. It is spring loaded and turns in the counterclockwise direction, which I guess makes sense to add advance.
I hooked my mighy vac hand pump on the cannister and pumped it up to 17 HGs and it didn't move. Also, I couldn't advance it by hand either at that point.
My car pulls about 16 to 18 HGs at idle. My questions are...
1) I presume this can is shot, right?
2) Should I stick with this B26 can?
3) Should there be that much load against the vacuum advance inside the distributor?
Le Mans Master
Joined: Apr 2004
Posts: 7,106
Likes: 38
From: Newark DE
the B26 adds 16º of advance starting at 5-7" HG and pegged at 11-13" HG so if your car produces 16-18" HG at idle the B26 should be fine. The B25 will also work at it's also 160 advance, starting at 5-7" HG all pegged out at 13-15" HG.
If your local store doesn't have a B26 in stock swapping to a B25 should work as well so see what they have.
If your local store doesn't have a B26 in stock swapping to a B25 should work as well so see what they have.
Le Mans Master
Joined: Apr 2004
Posts: 7,106
Likes: 38
From: Newark DE
Originally Posted by Jack71
What do you mean by pegged out? Full advance?
if you look at the specs on vacuum cans there are 3 importand specs to consider.
1. the amount of advance it will supply - in this case 8º of distributor advance (which is 16º of crank advance)
2. the level of vacuum it requires to start adding in advance - in the case of the B26 and B25 cans it's 5-7" HG.
3. the level of vacuum required to reach it's maximum amount of advance - on the B26 it's 11-13" HG, on the B25 it's 13-15" HG.
Usually you want a can that maxxes out or pegs out at an amount 2" below what your motor vacuum level is at idle
