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Distributor vacuum can specs (list)
https://slantsix.org/forum/viewtopic.php?t=13198		 Page 1 of 2
Author:  SlantSixDan [ Mon May 30, 2005 4:15 pm ]
Post subject:  Distributor vacuum can specs (list)
There have been some requests lately for specs on various vacuum advance cans. Here's info on the presently-available early and late style vacuum cans for the slant-6 distributor. These are Standard-Bluestreak numbers; they can be crossed to NAPA-Echlin numbers via napaonline.com if you wish. '72-up distributors can take either the early or the late style can. '71-down distributors can only take the early style can unless another hole is drilled in the upper breaker plate. "Start" is the amount of vacuum, in inches of Mercury, at which the can begins to supply advance. "Max" is the maximum amount of advance provided by the can in degrees, at the specified amount of vacuum in inches of mercury. First two listings are early types; remainder of listings are late types.

Number: Start / Max

VC-93: 4.9" - 7" / 5.25° - 7.5° @ 13"

VC-173: 7" / 5.3° - 7.8° @ 10"

VC-184: 7" / 7° - 10.5° @ 11.5"

VC-185: 9" / 7° - 10° @ 15.5"

VC-208: 6" / 10° - 12° @ 9" - 11"

VC-239: 7" / 7° - 10° @ 11.5"

VC-244: 9" / 7.5° - 9.5° @ 6" - 8"

I haven't ever tried installing a small-block V8 vacuum advance on a \6 distributor. It looks like it ought to work, and if it would (anyone?), there are additional options.
Author:  Dartvader [ Mon May 30, 2005 4:29 pm ]
Post subject: 
Thanks Dan. That is very interesting. Where did you find that info? Did you compile it from shop manuals? In theory, the last number,which is the inches of mercury required to hold that advance, can be adjusted by turning the adjustment inside. You can also increase the degrees of advance on any given canister by lengthening the slot in the arm that limits the plunger's travel in and out of then distributor. I made my 360 advance a full 25 degrees. By doing so I get 22 MPG on the highway with it.
Author:  SlantSixDan [ Mon May 30, 2005 5:20 pm ]
Post subject: 
Quote:
Thanks Dan. That is very interesting. Where did you find that info? Did you compile it from shop manuals?
From the Standard-BlueStreak catalogue. These are current-production units.
Quote:
In theory, the last number,which is the inches of mercury required to hold that advance, can be adjusted by turning the adjustment inside.
Yeah, I'm not sure which of these are adjustable, if any.
Author:  emsvitil [ Thu Jun 02, 2005 2:43 pm ]
Post subject:  A little more data....
Went to the neighborhood autozone to find a vacuum can for my 64 valiant today and got lucky.............

They had 1 mopar can in stock

Wells CV3015
listed applications
Dodge Truck 70-73
Dodge 71-72
Plymouth 70-72

Has a 9.5 on the arm (19 crank) and is adjustable

Found the following by watching for arm movement

At minimum setting:

Starts 5.5" Ends 10.5"

kept tightening the screw, and the 5" range stayed constant. Quit testing when I got it to start at 14" and end at 19" (still had some adjustment left)

Now for the best part. Other than the screw holes being slightly elongated as compared to the original, it's a perfect fit for my 64 without modifications. (and it cost $9.99)
Author:  Eric W [ Thu Jun 02, 2005 10:14 pm ]
Post subject: 
I thought the number stamped on the vacuum advance arm was the total number of degrees it advances (like 8.5 degrees only), not times two (17 degrees). Isn't the number on the governer multiplied times 2 for mechanical advance (like a governer stamped 11=22 degrees total mechanical advance if timing set at TDC)?
Author:  emsvitil [ Thu Jun 02, 2005 11:17 pm ]
Post subject: 
The number for the centrifugal governor and the arm on the vacuum advance can are both distributor degrees.

So it is 2x

BTW, I had measured the 6.5x can and got 14 at the crank, so with observational error, 2x is confirmed
Author:  sixsignet [ Sat Jun 04, 2005 2:20 pm ]
Post subject: 
Thanks, emsvitil and Dan.

I think this info will help slanted recurvers. Definitely helps me.

Apparently, two cans with 8.5R stamped on their arms can have very different characteristics.
Author:  Joshie225 [ Sat May 24, 2008 5:36 pm ]
Post subject: 
Time to bring this thread back from the dead.

Dan,

Do you have the advance numbers for the small block V8 vacuum advance cans? Looking at the small block and slant cans side-by-side I can't tell them apart. I need to order an advance can for my extra slant distributor and one for a small block distributor I'm setting up for a friend.
Author:  DusterIdiot [ Sat May 24, 2008 5:39 pm ]
Post subject:  That's the funny part...
Quote:
Do you have the advance numbers for the small block V8 vacuum advance cans? Looking at the small block and slant cans side-by-side I can't tell them apart. I need to order an advance can for my extra slant distributor and one for a small block distributor I'm setting up for a friend.
Funny part is when I looked these cans up by application at my parts place the catalog just lists the can by the 'year' like VC-185 was for something like all 1974 cars and trucks with 225/318/etc....

-D.Idiot
Author:  Aggressive Ted [ Sat May 24, 2008 7:24 pm ]
Post subject: 
Dan,

Thanks for the info on the cans but can you re- list them and add the number that is stamped on the arm???????

Thank you!
Author:  DusterIdiot [ Sat May 24, 2008 8:24 pm ]
Post subject:  Nope...
Quote:
and add the number that is stamped on the arm???????
That's not even listed in the parts catalog either... you should be able to 'guess' from his specs... I found it interesting that I got one of the VC-239 cans and the arm was stamped 8.5R... but it's a replacement for the super six distributor and should be stamped 11X...

:roll:


-D.Idiot

At least the VC-208 was 'spot on' for the Feather Duster curve...
Author:  Aggressive Ted [ Sat May 24, 2008 9:07 pm ]
Post subject: 
I like the VC-208 can too. I am running one of the Dart and one on the 69 Chrysler 440. I can get 19 mpg out of the 69 300 with a 10 to 1 motor driving back and forth to work and 23 mpg on the Dart driving back and forth to work.

I still would like to see how the other cans that Dan listed are stamped on the arms.
Author:  DusterIdiot [ Sat May 24, 2008 9:13 pm ]
Post subject:  Get the credit card out...
Quote:
I still would like to see how the other cans that Dan listed are stamped on the arms.
You'll have to buy one of each to find out... I know the VC-185 is stamped 8.5...

-D.Idiot
Author:  Aggressive Ted [ Sat May 24, 2008 9:57 pm ]
Post subject: 
Well that makes two we know what the arms are stamped.
VC-208 = 11R
VC-185 = 8.5R

Does anybody know what the rest are? :?: :?: :?: :?:
Author:  mpgFanatic [ Sun May 25, 2008 7:09 pm ]
Post subject:  should be 11x? Not necessarily.
Quote:
I found it interesting that I got one of the VC-239 cans and the arm was stamped 8.5R... but it's a replacement for the super six distributor and should be stamped 11X...
"Should be" stamped 11x? :) Yea, I went through the same mental gymnastics a few years ago, and I see I'm not alone. Most of these rubber diaphrams are apparently giving up the ghost at about the same age, so we're going to see a lot of people scratching their heads and asking these questions. The topic came up during the Valdosta race this weekend, actually.
Quote:
At least the VC-208 was 'spot on' for the Feather Duster curve...
YES. Exactly. That's what I found for mine, too, so I had to do some research to figure out why. And just now, I needed to go look through my notebooks to refresh my memory:

I've tested my particular car at a steady legal highway speed which corresponds to about 3000 rpm, with the O2 sensor showing as close to stoichiometric as I can get it or maybe just a whisker on the lean side, and I have mapped a lot of curves on graph paper. I found that this engine's minimum fuel burn occurs at a TOTAL advance (centrifugal + vacuum) of 44 or 45 degrees (when running pump premium fuel). I'm becoming ever more convinced that the factory knew this information, too, because that's about exactly where this car was set up in stock configuration.

So, what happens when you ditch the old, heavy centrifugal springs, as so many of us have done? (And what are the odds of any other type of person caring enough to replace a worn diaphram?)

All of a sudden, the centrifugal advance at 3000 rpm jumped quite a bit, because the weights are now allowed to swing all the way out to their full 25 (crank) degree of travel. To match that, the newer manufacturing of vacuum cans needs to be correspondingly reduced, and the old 11x (distributor) degree is simply too much (unless you set the base timing near zero.) By coincidence, the new advance springs and the new canisters end up delivering a total advance in just about the same ballpark. Or maybe not such a coincidence.

Although for years I've been very hesitant to publish numbers regarding what works on one particular vehicle, for fear that someone would take it as gospel, maybe it's not quite as specific as I thought. I was truly surprised to see that none of the "rule-of-thumb" guidelines I'd developed changed at all, after rebuilding the engine from an advertised 8.5 CR to a measured 9.5 CR. At each point in the mapped curve, the new engine is happier with about 1 or 2 degrees less advance during acceleration, but the highway fuel mileage still depends on a 44 degree total.

- Erik
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