Was thinking of adding a vacuum advance canister

Discussion in 'Small Block Tech' started by Mark Demko, Nov 6, 2018.

  1. Mark Demko

    Mark Demko Well-Known Member

    Im thinking of adding a vacuum advance canister to my MSD 8548 Pro Billet distributor IF its even possible.
    Is it worth it during highway driving or am I just setting myself up for issues?
    I've been running this distributor for years and haven't had any issues NOT using vacuum advance.
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    AFAIK, it isn’t possible. Call MSD to confirm. On a street driven car, it’s a plus for sure.
  3. 72gs4spd

    72gs4spd Well-Known Member

    I agree with Larry. I contacted MSD and they said it wouldn't work. I found a brand new Mallory on ebay and bought it instead.
  4. Stevem

    Stevem Well-Known Member

    If your driving it on the street no less highway miles I would go as far as spending the money to get a Dizzy in the motor that has vacuum advance, maybe you could even borrow one!?

    You don't realize how much unburned fuel is wearing out your cylinder walls and getting into your oil during part throttle and cruse times!

    Even if your only able to add in just 8 degrees of advance it's worth it cost wise!
    If you need real world proof then find a nice long flat stretch of road that you can do 55 mph on and bring your timing light along.
    Drive that stretch of road and the stop and add in 6 to 8 degrees more base timing and make the drive again and see what you think!
    Last edited: Nov 9, 2018
    BadBrad likes this.
  5. Mart

    Mart '71 350 GS, almost stock

    Mark, Question/answer from Summit:

    I have previously purchased a 8548 distributor which works fine; however, I could really do with a vacuum advance. Does MSD make a distributor to fit the Buick 215 that has a vacuum advance?

    Thanks in advance

    Asked by ALLAN on May 12, 2018

    Thank you for your question. MSD does not offer a vacuum advance version of the 8548 Pro-Billet distributor. However, we do offer a similar distributor from Pertronix under part number PNX-D351710.

    [​IMG]Summit Racing Answer - August 02, 2018

    ....And you don't want to buy a Pertronix!:rolleyes:
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    300sbb_overkill likes this.
  7. Mart

    Mart '71 350 GS, almost stock

  8. Mark Demko

    Mark Demko Well-Known Member

    Thanks for the info guys:cool:
    I was thinking about it some more,and I think Im going to leave well enough alone, I've had zero issues with my MSD set up since install way back when.
  9. Mart

    Mart '71 350 GS, almost stock

    That's actually a good idea. The 8548 non-vacuum 350 dist. needs an MSD box. The 8552 doesn't, and it has the vacuum advance PLUS a built in Rev limiter!
  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    If I was a 350 guy, I'd be calling MSD and seeing if I could enlighten them.:) They might not be aware of that fact.
  11. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Or if they say no, ask to buy one if the 455 distributors without a gear and buy the 350 gear from them at same time.

    Probably would get done faster if you asked someone like Summit to ask them for you, have them enlighten them?
  12. Mart

    Mart '71 350 GS, almost stock

    Nope, just the opposite. Summit didn't have a listing for a 350 dist gear when I ordered mine. Had to deal directly with MSD, and they would not pull one off a stock dist to sell either, I tried. Hopefully they now have a part # for replacement 350 gears.

    Vacuum advance may be beneficial with my cam as my high maintaince girlfriend says my car stinks and is gassing her out!:rolleyes::D
    Might help at idle with 35* overlap.
    Mark Demko and Kennybill like this.
  13. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    That would be the spoiler, if they don’t sell the replacement gear. Asking them to sell you a RTR 455 distributor without the gear is probably too much work for them. Just buy the 455 distributor and the 350 gear at the same time would be the way to go IMO.
  14. Schurkey

    Schurkey Silver Level contributor

    Is this like the other MSD distributors which have a .500 shaft, so a "stock" gear has to be honed-out to fit? OEM diameter is .491 or something close.

    Does MSD actually sell a 350 gear suitable for their distributors?
  15. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Well they do make this distributor with a 350 gear on it,


    I was thinking that you could put that gear on this distributor and have vacuum advance.


    Would add to their Buick product line for very little cost. Has anyone suggested this to MSD?

    Schurkey, have you read this entire thread?:)
    Last edited: Dec 15, 2018
  16. Mart

    Mart '71 350 GS, almost stock

    Yep, MSD with vacuum advance for the 350, that would be the ticket. As soon as I get closer into 'distributor mode', I might check to see what's possible.
  17. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Didn't you just buy a new dist. gear? If so you can get the 455 distributor and swap the gear.
  18. Mart

    Mart '71 350 GS, almost stock

    Yup, if I find a 455 vac dist. for a good price, I'll have the setup. Or I can lockout timing and go with start retard. Won't help at cruise around town advance though, but will keep high maintenance happy at idle.
    Will manifold vac function a dist properly with only 5" ?
  19. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    You should have more vacuum at cruising speeds than what you have at idle, especially when you're in O/D I would think, WOT though would go to zero.
  20. Mart

    Mart '71 350 GS, almost stock

    Not as concerned at cruise speeds, more so at idle. Will 5" actuate the vacuum can diaphragm fully at idle??

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