Vacuum advance can "chart"
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Vacuum advance can "chart"
So, I recently bought a new distributor advance can for my truck and this chart came with it. I bought a "Standard Motor Products" can.
My understanding is that these are all "Ford" distributor part numbers and somehow the company compiled all of these specifications to accommodate your installation with the particular vehicle that you are putting it in. Thus, setting the correct amount of vacuum advance that was required (originally) from the factory for the particular vehicle using the corresponding distributor P/N.
The more that you turn the screw inside in the CCW direction, the less vacuum advance you will have. i.e. 3 turns out will allow more advance than 5 turns out.
I had some correspondence on the matter with "72 3/4 ton" and "Jeffafa" and thought I would go ahead and start a thread because 72 34 ton had some good questions on the matter and thought maybe it would help give folks a baseline with which to start tuning their vacuum advance (if needed). Hope this is of some help or good discussion to all.
Dan
My understanding is that these are all "Ford" distributor part numbers and somehow the company compiled all of these specifications to accommodate your installation with the particular vehicle that you are putting it in. Thus, setting the correct amount of vacuum advance that was required (originally) from the factory for the particular vehicle using the corresponding distributor P/N.
The more that you turn the screw inside in the CCW direction, the less vacuum advance you will have. i.e. 3 turns out will allow more advance than 5 turns out.
I had some correspondence on the matter with "72 3/4 ton" and "Jeffafa" and thought I would go ahead and start a thread because 72 34 ton had some good questions on the matter and thought maybe it would help give folks a baseline with which to start tuning their vacuum advance (if needed). Hope this is of some help or good discussion to all.
Dan
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From: NAMPA, ID.
Since the gasoline octane rating is much less today than what it was in the early 70's, this chart is pretty much useless. Ideally you want as much vacuum advance that the engine will accept without spark knock.
Hotshot
Joined: Mar 2013
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From: Phoenix, Az.
I don't think this chart is useless. Just the opposite. I think it is a very good baseline start when someone buys a Dizzy or replacement can. Like Orich said. When someone buys an aftermarket part who knows where they adjusted it at their factory? One turn? 3 turns? Where ever in the heck their worker felt like? With this chart we can set a replacement part where Ford did originally. 
Then experiment from there with more (or less) advance until we find the Sweet Spot. And furthermore, If anybody needs the engineering numbers off their engine's original Dizzy they can PM me anytime.
I'd rather sho*t at a target than sho*t in the dark.
I say Good Job Dan.
Then experiment from there with more (or less) advance until we find the Sweet Spot. And furthermore, If anybody needs the engineering numbers off their engine's original Dizzy they can PM me anytime.I'd rather sho*t at a target than sho*t in the dark.
I say Good Job Dan.
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I don't think this chart is useless. Just the opposite. I think it is a very good baseline start when someone buys a Dizzy or replacement can. Like Orich said. When someone buys an aftermarket part who knows where they adjusted it at their factory? One turn? 3 turns? Where ever in the heck their worker felt like? With this chart we can set a replacement part where Ford did originally. Then experiment from there with more (or less) advance until we find the Sweet Spot. And furthermore, If anybody needs the engineering numbers off their engine's original Dizzy they can PM me anytime.
I'd rather sho*t at a target than sho*t in the dark. I say Good Job Dan.
Then experiment from there with more (or less) advance until we find the Sweet Spot. And furthermore, If anybody needs the engineering numbers off their engine's original Dizzy they can PM me anytime.I'd rather sho*t at a target than sho*t in the dark.
I say Good Job Dan.
Dan
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Joined: Mar 2013
Posts: 14,255
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From: Phoenix, Az.
But since I am here, There are 17 different Dizzy numbers for 1966 Full Size cars and T-Birds.
Out of the 17, 5 of them show up on the chart.C6AF-AH..(Police Car) ...3 turns.
C6AF-E.........................4 1/4 turns.
C6MF-A........................3 3/4 turns.
C6SF-B.........................4 1/4 turns.
C6SF-D.........................4 1/4 turns.
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Post Fiend
Joined: Apr 2002
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From: Waterloo, Iowa
As a practical matter those "3.5 turns" spec or whatever the case, would only be correct if, the initial crank and internal distributor advance were still set at the factory advance curve. Not likely. Lots of folks run a whole lot more initial and then limit the mechanical, and install lighter springs. This will also change the amount of manifold vacuum (somewhat) signal at different RPM. I mean, the figures are a place to start but not really all that useful. Each engine is going to be a bit different anyway.
Many if not most vac can instructions just suggest starting at the max vacuum advance (clockwise for ex.) and then backing off in 1 or 2 turn increments till it stops pinging.
To be clear the vacuum advance is disconnected and plugged unless and until the "total" (initial + mechanical) advance is sussed out. The vacuum advance is reconnected and adjusted only when everything else (timing wise) is complete.
Many if not most vac can instructions just suggest starting at the max vacuum advance (clockwise for ex.) and then backing off in 1 or 2 turn increments till it stops pinging.
To be clear the vacuum advance is disconnected and plugged unless and until the "total" (initial + mechanical) advance is sussed out. The vacuum advance is reconnected and adjusted only when everything else (timing wise) is complete.
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