Advanced Distributing for Studebakers.
earlier post, I obtained and rebuilt one of these Delcos, using a core graciously given to me by Warren Webb, one of the regulars on the Studebaker Drivers Club Forum.
At the time I built it, however, I installed a vacuum advance specified for a 1961 Impala, figuring (wrongly) that a vacuum can is just a vacuum can. I should have known better! What I've found out since is that not all cans are equal. On this Forum thread, Joe Hall notes that the can commonly sold for Studebaker applications (NAPA VC680) is actually 2 degrees shy of the Studebaker OEM advance setting for V8 cars.
It turns out that nearly all of these vacuum advance units are all manufactured by Dana Engine Controls, now owned by Standard Motor Products, so no matter what brand you buy, it's the same part in the box. The trick is determining the right part. And there are about 25 different cans, each with a different setting for the point at which full advance kicks in. So how do you identify them?
Dana stamps a number on the mounting bracket of each advance unit. Each number corresponds to an advance profile that denotes how much vacuum must be applied to achieve full advance. It turns out, according to Joe Hall's research, that the Studebaker part number is "B20." The VC680 that NAPA's system specfies is "B1". Obviously the wrong part.
Thanks to the guys on the Corvette forums, who know their stuff when it comes to Delco parts, I found out the difference in the two parts' advance delivery settings:
- VC680 (stamped "B1") delivers 0 degrees of advance until 8" of vacuum, and 16 degrees of advance at 16" of vacuum.
- VC1765 (stamped "B20") deliver 0 degrees of advance until 6" of vacuum, and 16 of advance at 12" of vacuum.
Replacement is easy, and doesn't require removing the distributor from the car. Just unplug the coil wire and undo the two spring-loaded screw clamps that hold the distributor cap on, and move it out of the way. The screws that hold the vacuum advance to the distributor base are accessible from the passenger side of the car once the cap is removed.
Installation, as they say, is the reverse of removal. Once it's all back together, don't forget to check the timing and reset the idle if need be.
For some interesting reading about vacuum advance, check out this post from the Vetteclub Forum, and the aforementioned paper from Lars Grimsrud. You'll find out everything you need to know and more!