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AS-20 vacuum can

Old 11-09-2018, 05:30 PM
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stumpshot
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Default AS-20 vacuum can

Got one on my bench. Checked it with a mity vac. About 8lb starting and all done by 14.
Can't find info on line for this number and no wrenches seem to turn an adjuster so I don't think it's an adjustable.
Wondering if it's made this way or shot.
All my distributors are HEI and it came out of one of those 3.
Thanks
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Old 11-09-2018, 07:54 PM
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I remember when I purchased a adjustable Vac Can, the instructions stated not to turn the allen screw all the way out or damage will occur. If you can't feel a allen screw through the port with a wrench, its a std, non-adj unit or broke, which I doubt. As far as I know, adjustable units were after-market add-ons.

At one time, Lars had a complete list of GM Vac Cans on this forum with part numbers. Maybe that AS-20 was on there.

Last edited by HeadsU.P.; 11-09-2018 at 07:55 PM.
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Old 11-09-2018, 08:12 PM
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Yeah. I checked Lars' vac can stuff for HEI and non HEI distributors. Didn't see this number. Kind of a strange unit I guess. Only one I have with any stamp marks on it.
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Old 11-09-2018, 08:46 PM
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I think the AS-20 was an Accel product. There is one listed on ebay and it says it's for a 68-70 Olds Tornado 442.
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Old 11-09-2018, 08:53 PM
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Good info. Thanks Canada. Must have been the one in the 350 before I swapped the distributor. Quite possibly it's for a non HEI then.
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Old 11-09-2018, 11:44 PM
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Originally Posted by stumpshot View Post
Got one on my bench. Checked it with a mity vac. About 8lb starting and all done by 14.
Can't find info on line for this number and no wrenches seem to turn an adjuster so I don't think it's an adjustable.
Wondering if it's made this way or shot.
All my distributors are HEI and it came out of one of those 3.
Thanks
The AS-20 is an Accel adjustable vacuum advance. Get rid of it and buy a vacuum advance with known specs: The "adjustable" units are only adjustable for diaphragm spring pre-load, and cannot be adjusted for length, which is the critical factor. That AS20 will give you a vacuum advance curve that's about 20 degrees long, which is not suitable for a street driven vehicle.

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Old 11-10-2018, 11:47 AM
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Perhaps that's why somebody came up with that bracket that limits the Vac adv. It installs under one of the canister screws, has four options for max adv by simply flipping the unit around. I believe I got mine from Mr. Gasket. Years ago, if memory serves me, I believe the bracket came with a MSD StreetFire. I still use it today on another dizzy with the notch set at 10-13 degrees limit position. Somebody sells those limiter brackets. Don't know who / where.

Currently not running a Adj-Vac-Can but was considering switching to one, sitting on the work bench.

Last edited by HeadsU.P.; 11-10-2018 at 11:51 AM.
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Old 11-10-2018, 11:59 AM
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Thanks to all for figuring this out. I'm putting on a AR12 but decided to bench test all the junk I've got rolling around in my parts pile. Strange thing about this unit is that I can't find an adjuster and at full pump the rod moves just over 1/8". It's going in the trash anyhow. Got to thin a few hundred pounds of crap out of the garage.
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