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Discussion Starter #1
Anyone know were I can get an adjustable vacuum advance canister for an MSD 8361? The one on it is way too much, I don't want more then 10 deg and I'm getting close to 25.. Right now I have it blocked off and want to use it.
 

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I had that problem too. your engine probably pulls a lot of vacuum.

I believe on the adj vac adv cans you can use a limiter plate to stop the total amount of advance.
 

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Discussion Starter #3
I have 15 in of vacuum which I don't think is allot but, I think this vacuum canister is just to sensitive.. I have found that the Accel 31034 would work but, I'm not sure.
 

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Looks like this is the Vac advance unit in it which you're right, might be just a tad too sensitive and pulling in too soon. Although that unit only provides a total of 8° additional advance.

VC1808 B26

Starts at Hg. = 5-7

Max Dist, Degrees 8° @ 11-13 Hg.

So it is only providing 8° of additional advance but probably too soon. Full advance at 11 - 13 HG. probably an advance unit for a much more radical cam. Yeah get an adjustable and limit it to 10° that's a good starting point. I run about 10° on my ZZ383, any more and PING. 42° total when initial, centrifugal and vacuum is all added up. Without the vacuum advance though the fuel mileage goes right out the window along with idle quality.

A B13 might be better suited...

Starts at Hg. 9-11
Max Dist. Degrees 8° @ 16 - 18 Hg.

Maybe a B21...

Starts at Hg. 7-9
Max Dist Degrees 10° @ 16 - 18 Giving you 10° of additional Vacuum advance, that's what my motor seems run best at.
 

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Discussion Starter #5 (Edited)
Looks like this is the Vac advance unit in it which you're right, might be just a tad too sensitive and pulling in too soon. Although that unit only provides a total of 8° additional advance.

VC1808 B26

Starts at Hg. = 5-7

Max Dist, Degrees 8° @ 11-13 Hg.

So it is only providing 8° of additional advance but probably too soon. Full advance at 11 - 13 HG. probably an advance unit for a much more radical cam. Yeah get an adjustable and limit it to 10° that's a good starting point. I run about 10° on my ZZ383, any more and PING. 42° total when initial, centrifugal and vacuum is all added up. Without the vacuum advance though the fuel mileage goes right out the window along with idle quality.

A B13 might be better suited...

Starts at Hg. 9-11
Max Dist. Degrees 8° @ 16 - 18 Hg.

Maybe a B21...

Starts at Hg. 7-9
Max Dist Degrees 10° @ 16 - 18 Giving you 10° of additional Vacuum advance, that's what my motor seems run best at.
Were do I get this VC1808 B21 or B13?? and will it fit a MSD 8361?
 

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I don't want more then 10 deg and I'm getting close to 25.. Right now I have it blocked off and want to use it.
Why do you not more than 10degree?

It's not a lot of timing at 50°-60° total at cruise.

Al
 

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Discussion Starter #7 (Edited)
I'm not talking total, I'm talking at idle.. I have 14 deg initial and with the vac advance connected, it jumps to 40. Thats way too much based on what I have found, should not be more then 25 at idle. I get total with the vac off of 38 total. With the vac connected it would be 63..
 

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I'm not talking total, I'm talking at idle.. I have 14 deg initial and with the vac advance connected, it jumps to 40. Thats way too much based on what I have found, should not be more then 25 at idle. I get total with the vac off of 38 total. With the vac connected it would be 63..
This is normal!

And are you checking it in gear?

What have you found? (not being a SMART "A")
What someone said!

For a street driven car this is normal.

Understand the vacuum under acceleration drastically fluctuates!

Unless your having detonation I would not change it.

AL
 

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Discussion Starter #10
Can't check it in gear, its a 5 speed.. From everything I have seen, it all states that at an idle, the vac advance should add about 10 - 12 deg of advance.. 25 sounds like a bit much.. I'll dig up what I found and post it.
 

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Discussion Starter #11
If you read both of these unless I'm reading it wrong, my dizzy vac advance is adding way too much at an idle. My total if you add it up is 61 deg.. 14 deg initial, 25 deg added with the vac advance and another 22 deg for mechanical. Here are two of the things I have based my need to change the vac canister (along with a few people here). Based on both of these, I should not go beyond 54 deg max. VacuumAdvance
Timing101
 

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Discussion Starter #12
This is normal!

And are you checking it in gear?

What have you found? (not being a SMART "A")
What someone said!

For a street driven car this is normal.

Understand the vacuum under acceleration drastically fluctuates!

Unless your having detonation I would not change it.

AL
BTW, when I hook up the vacuum advance, it increases the RPM soo much I can't get the idle down were it should be..
 

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At idle it sounds like the vacume advance pulls in enough advance that the weights on the mechanical advance probably start moving if you have light springs on it-this compounds the problem. I usually make an adjustable limiter out of a piece of tin so I can add vacume advance a little at a time untill I hear ping at a light load under cruize conditions then pull some back out. The trouble I have found with the adjustable units is they don't limit travel from what I've seen- they only change the amount of vacume needed to make them work.
Also, you can hook the vacume advance line to a ported vacume source instead of manifold vacume if you don't want it to affect your idle but I've found on most performance engines manifold vacume does work the best.
Bob
 

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Discussion Starter #14 (Edited)
At idle it sounds like the vacume advance pulls in enough advance that the weights on the mechanical advance probably start moving if you have light springs on it-this compounds the problem. I usually make an adjustable limiter out of a piece of tin so I can add vacume advance a little at a time untill I hear ping at a light load under cruize conditions then pull some back out. The trouble I have found with the adjustable units is they don't limit travel from what I've seen- they only change the amount of vacume needed to make them work.
Also, you can hook the vacume advance line to a ported vacume source instead of manifold vacume if you don't want it to affect your idle but I've found on most performance engines manifold vacume does work the best.
Bob
Yup, tried the ported vacuum, does not really work the way it should.. I setup my mechanical advance to be all in by 2800rpm (don't recall which springs I used). But now that you say that, I'm going to re-check that tonight.
 

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Discussion Starter #16 (Edited)
Well, this was a learning experience!! Got it fixed... I had springs in the dizzy that were way to light. The other thing I found was with the base plate. I have a procomp (I think that's the name) base plate and if you remember I stated that when I hooked everything up I could not get the idle down any further then about 1400 rpm at best. Unless I unhooked the vacuum from the dizzy.

Well, it turned out the the secondaries were not closing all the way no matter what I did with the adjustment on the pass side of the base plate. Turned out that the slot that a rod slides in that engages the secondaries (on the driver side) at WOT was not allowing them the totally seat at an idle.. The slot in the plate mounted on the rod that the secondaries mount too was too short by about .030.. So I fixed that and everything started to fall into place.. :D

I re-installed the MSD vacuum canister and it works fine. So, I have an adjustable vacuum canister that I'm not using. No biggie, I learned allot!!
 
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