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Thread: Correct Vacuum Advance For Window Type Delco Distributor

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    Silver Hawk Member JoeHall's Avatar
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    Correct Vacuum Advance For Window Type Delco Distributor

    The vacuum advance for "window type" Studebaker Delcos will physically interchange with most 1950s-1970s GM vehicles. For that vast range of application, there were originally at least 25 different part numbers, with important differences in the operational specs; primarily, vacuum required for full advance, and total degrees of advance. However, vacuum advance technology ceased in the 1970s and has became almost forgotten technology. So now days, VAs have became a one size fits all, as long as it physically fits. The one size fits all for GM vehicles is Echlin #VC680, which is readily available at FLAPS for $10-15, and is also referenced on this NG as a replacement for Studes. It is also the same one I removed from a Stude distributor a couple days ago.

    The problem is, the Stude VA is supposed to advance 16 degrees at 12 inches' vacuum, but the VC680 only advances 12 degrees, and requires 16-18 inches' vacuum to do so. So that vac advance will almost certainly result in lost pep and MPG in a Stude. In researching VA specs on-line, the closest to Stude I found was VC1812, which advances 12 degrees at 12-14 inches' vacuum. With that VA on a Stude, the 2 degrees' less advance could be offset by advancing the timing a couple of degrees.

    I found a better answer at Summit, with an adjustable VA, made by Accel. A couple of other companies also make the adjustables. Will report more when I receive it.

    Bottom line, for anyone running a window type Delco in a Stude, if you are not satisfied with MPG or pep, the VA is a good place to look when it comes to troubleshooting.

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    I've been using the adjustable Crane vacuum advance units for the Delco window distributor. I have a distributor machine and with the adjustable advance, I can accurately adjust vacuum advance for Studebaker engines. The one size fits all advance works but isn't the best in terms of performance. Bud

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    Quote Originally Posted by JoeHall View Post
    The vacuum advance for "window type" Studebaker Delcos will physically interchange with most 1950s-1970s GM vehicles. For that vast range of application, there were originally at least 25 different part numbers, with important differences in the operational specs; primarily, vacuum required for full advance, and total degrees of advance. However, vacuum advance technology ceased in the 1970s and has became almost forgotten technology. So now days, VAs have became a one size fits all, as long as it physically fits.

    Bottom line, for anyone running a window type Delco in a Stude, if you are not satisfied with MPG or pep, the VA is a good place to look when it comes to troubleshooting.
    Joe is right as usual, mostly. Having the correct vacuum advance is a major factor in maximizing highway cruise fuel economy. Studebaker and Packard had several different vacuum advance specifications depending on compression ratio, weight, transmission and axle ratio.

    However, it has little to do with pep. When the throttle gets down to "pep", manifold vacuum and the advance from it has dropped and centrifugal advance takes over as the RPMs rise.

    jack vines
    PackardV8

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    Silver Hawk Member JoeHall's Avatar
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    Bud, I wish I had one of those machines. My plan is to adjust the Accel to where it pretty much matches an older type, Delco VA I have. Pretty sure I can come close to vacuum required by using my mouth, and a dial indicator will get the actuating arm travel plenty close enough.

    Jack, I am thinking more pep at light to moderate throttle also; the ignition will advance farther, and remain advanced longer (till vacuum drops below 12 inches). Should also result in less pedal travel to maintain steady road speed, including slight hills, up to around 60-70 MPH when vacuum drops too low. Of course, when vacuum drops below the point where it begins to advance the VA, say 5 inches, the VA then becomes a non issue, as you said.

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    A pretty decent job mapping the vac advance can be done on the car with a "dial back" timing light and mighty vac. A standard timing light would be suitable if the damper was prepared adding some degree marks using A little geometry, since unfortunately "timing tape" which converts dampers into degreed dampers is not applicable to narrow plate Studebaker dampers. Some would say adjustable timing lights are innaccurate, which could also be checked with a degreed damper. Gotta keep the rpm constant, or make a centrifugal advance map with vac line disconnected, which is a good idea anyway.

    Apparently a "tune up" included all this and more back in 1952.
    http://chevy.oldcarmanualproject.com.../5204mts00.htm

    The same chevy.oldcarmanuaproject.com site has a lot of fun and valuable info. Some is of questionable authority, so must be viewed or especially used with caution.
    http://chevy.oldcarmanualproject.com...p23/index.html

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    Silver Hawk Member JoeHall's Avatar
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    I received the adjustable VA from Summit. It allows plenty of adjustment of both degrees & advance, and looks like the ultimate one-size-fits-all for pre-1975 vehicles with Delco window type distributor.

    Earlier, I tried hard to find a VA with the correct specs at FLAPS. Reading on the internet, I discovered there have been many suppliers over the decades, and, consequently, many part numbers. However, all suppliers used the same "ID" numbering system; it is stamped on the actuating arm, usually with a 'B' prefix. With that ID, you can determine the application, no matter what part number is on the box, or who made it.

    I researched and found three part numbers from yesteryear, with correct spec for Studebaker, still in NAPA and AutoZone systems. So I ordered AutoZone part #DV1465, which crossed toNAPA's Echlin VC1765; both those VAs should have ID #B20 stamped on them, which is the "boss" number. The one from AutoZone had a B1 stamped on it, which is the one-size-fits-all available everywhere. Looks like now days, no matter what number you order, the same B1 is inside the box. That B1 is correct for 1965-66 Stude V8, and a kajillion GM cars, but is NOT correct for Stude V8. I did not bother to try NAPA, and now that I have the Accel, it is a non issue.

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    Chief Cat Herder showbizkid's Avatar
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    After reading this thread, I realized that my fuel mileage problems are likely due to the wrong vacuum advance unit, so I did some research and found that Joe's VC1765 part is indeed the correct application for Stude V8. In addition to "B20", "B26" is the same advance profile.

    I went to NAPA and ordered one, but it took two tries - the first one that arrived from warehouse had the wrong part in the box with a hand-written label on it identifying it as a part number different than that stated on the box. The second time, the correct part was in the box, with the "B20" stamped on it.

    So if you're not inclined to use the adjustable advance, the correct part IS available, although it may take more than one try to get it
    Clark in San Diego
    '63 Standard (F2) "Barney"
    http://studeblogger.blogspot.com

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    Silver Hawk Member JoeHall's Avatar
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    Clark,
    Sounds like you climbed a learning curve on modern vac advances, as I did. The ones from modern FLAPS are considered "close enough" for classic cars, which most owners do not drive very much anyway. The correct VA should result in a little more pep and MPG. Similar to the adjustable VA, you can use the timing mark to advance timing to where the motor is running optimal; usually 2-6 degrees advanced over OEM specs.

    I am probably gonna offer that setup to someone soon (adjustable VA, rebuilt window distributor, Pertronix Ignitor II, Accel coil, etc.), as I plan to go to EFI on that car.

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    Chief Cat Herder showbizkid's Avatar
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    For anybody who wants to really learn about this stuff, here's a very in-depth treatise on the subject from a fellow named Lars Grimsrud from Lafayette, Colorado, who seems to really know his stuff!

    http://www.lbfun.com/warehouse/tech_...ance_Specs.pdf
    Clark in San Diego
    '63 Standard (F2) "Barney"
    http://studeblogger.blogspot.com

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    I don't know where you guys are getting your specs from for the VC1765 B26 but I have seen max 8 @ 11-13" listed so if you can point me to where the specs that you got that match with that vacuum unit are listed I would be happy. I have one of those units on order but the specs don't match with Studebaker specs so I will cancel the order at the end of the day and order a Crane adjustable unit unless someone can come up with the listing with the correct Studebaker specs for the VC1765 B26. Len.

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    Silver Hawk Member JoeHall's Avatar
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    Clark that is one of the on-line sources I ran into when researching it before. I agree, that guy really knows his stuff.

    Skybolt you are correct in the specs for VC1765 B20/B26, but it is next best (that is commonly available). The VC1812 B30 is closest to OEM Stude spec, with 12 degrees @12-14"). As mentioned, a person could make the best of the situation with the VC1765, by advancing the a few distributor timing a few degrees.

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    Silver Hawk Member JoeHall's Avatar
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    Skybolt,
    Probably most important to note, is the B# stamped on the lever is the ONLY way to know for sure which VA you are getting. If there is a discrepancy between the box number, invoice number, or anything else, the B# is senior. What I found was B1 was being used as a one size fits all; used to fill the bill for whatever part number the book called for in any particular vehicle. Put another way, if it says B1, it doesn't matter what the box calls it, its a B1. So if you decide on buying one at FLAPS, don't pay till you open the box and make sure the B# you want is what is inside.

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    Chief Cat Herder showbizkid's Avatar
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    Just as Joe says! Len, check out the link I posted in #9 above - the fellow gives all the specs for all known types.
    Clark in San Diego
    '63 Standard (F2) "Barney"
    http://studeblogger.blogspot.com

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    Thanks showbizkid, that explained what the numbers equate to. So, a vacuum advance control unit with 8 degrees of maximum advance produces 16 degrees of ignition advance in relationship to the crankshaft therefore a vacuum advance control unit producing 16 degrees of crankshaft advance would be an 8-degree vacuum advance control unit like the VC1765 B26 with 8 @ 11-13" listed. Brilliant.

    Joe, The one I ordered had the B26 on the unit. But to be sure I will check before walking out of the store.

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    Silver Hawk Member JoeHall's Avatar
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    Quote Originally Posted by Skybolt View Post
    Thanks showbizkid, that explained what the numbers equate to. So, a vacuum advance control unit with 8 degrees of maximum advance produces 16 degrees of ignition advance in relationship to the crankshaft therefore a vacuum advance control unit producing 16 degrees of crankshaft advance would be an 8-degree vacuum advance control unit like the VC1765 B26 with 8 @ 11-13" listed. Brilliant.

    Joe, The one I ordered had the B26 on the unit. But to be sure I will check before walking out of the store.
    That's the part I forgot ! The degrees' advance are doubled, when comparing to OEM Stude specs, due to the 2:1 ratio as you say above.

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    Just picked up the unit from NAPA. VC1765 with B26 on the flat side of the arm. About $14.00. Bargain.

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    Silver Hawk Member JoeHall's Avatar
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    Quote Originally Posted by Skybolt View Post
    Just picked up the unit from NAPA. VC1765 with B26 on the flat side of the arm. About $14.00. Bargain.
    Great ! Love it when a plan comes together huh?

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