Power Timing your Buick V8

Discussion in 'Buick FAQ' started by LARRY70GS, Jan 2, 2005.

  1. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Retarded timing heats an engine up, not advanced timing. Light load cruise timing should be in the low to mid 40's for timing. All in by 3500 is fine. Supplement the rest with vacuum advance. Limit the vacuum advance to 12* and you will be at 45* while cruising. If the engine still heats up on the highway, you probably have a radiator problem.
    2nd Gen Buick Fan likes this.
  2. 2nd Gen Buick Fan

    2nd Gen Buick Fan Platinum Level Contributor

    Thanks for the input, Larry. I think I'm good with the mechanical and initial timing now, but the vacuum advance canister is kicking my butt. I bought an Accel 31034 adjustable canister in 2019 and limited the pull on the unit with a small plate (like the pictures at the beginning of this FAQ thread). It's good at limiting the vacuum advance to 12*, but my engine "rattles" whenever the vacuum advance canister is connected to either manifold or ported vacuum on the Q-Jet and I attempt to accelerate with anything more than a gentle pedal. I'm pretty sure this is knocking. The engine runs like a beast without the vacuum advance and sounds great, but at 9-10 MPG. On this Accel 31034, there is no "fully counterclockwise" position that I can determine (per their instructions). The hex wrench spins infinitely in either direction. When the vacuum advance is connected, the car gets 12-13 MPG and runs 5 degrees cooler (but sounds like crap). Time for another vacuum advance canister and I'll run it without for now.

    Attached Files:

  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    It rattles because the vacuum advance doesn't go away fast enough. I thought the amount of advance was adjusted through the vacuum nipple on the Accel unit. What you need to adjust is the spring tension so that the vacuum advance drops off instantly with moderate throttle. More spring tension raises the vacuum level necessary to overcome the spring tension, so advance is only there at high vacuum levels ( low load), but goes away quicker under high load. It can be a balancing act between amount of advance and spring tension. I like to use a plate on a stock canister because spring tension on them is pretty high.
    2nd Gen Buick Fan likes this.
  4. 2nd Gen Buick Fan

    2nd Gen Buick Fan Platinum Level Contributor

    I purchased another Accel 31034 adjustable vacuum advance canister and determined that you have to push the hex key in very hard to engage the spring so it will turn (like fingers bleeding). The sweet spot for my car seems to be 7* initial, 20* mechanical and 10-12* on ported vacuum. I could get away with more initial timing until the engine was fully warmed up, but then the engine knock started. Car runs great now! I really appreciate this forum. If anyone wants a list of which McMaster Carr or Grainger springs work well for Delco distributors. I have some part numbers matched to the RPMs where the mechanical timing was all in.
    FirstBuickNut and 69GS430/TKX like this.
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    That's great, but realize at wide open throttle, you will only have 27* of timing. That is likely leaving power on the table.

    The engine knock starts with only 7* of initial timing? That is strange.
    TimR and 69GS430/TKX like this.
  6. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    Is everyone still using the Crane and Mr. Gasket kits for their recurve or are there other kits out there now?

    I need to find a decent adjustable vacuum canister for my points distributor. Seems the Crane kit is no longer in stock at most retailers.
  7. 2nd Gen Buick Fan

    2nd Gen Buick Fan Platinum Level Contributor

    I struggled last year to find something that was in a kit that wasn't way loose (mechanical advance at idle) or way tight (all in above 4,000 RPM). I ended up buying springs through McMaster Carr and Grainger that were similar to what used to be included in the kits. I can post the part numbers from those vendors if you think it would help you. This is on a stock Delco distributor.
  8. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    I do have a few different spring kits from over the years and the combo in my distributor now seems to be a good fit.

    I have to leave my vacuum advance unplugged though because there is just too much part throttle timing at cruise and the vacuum advance doesn't go away quick enough at WOT.

    I know I had a crane canister with the modified limit plate location in an SBB distirbutor but I think that is long gone now.

    It looks like the Accel 31034 might be an option but I don't think it includes a limit plate so I'd have to make one.
  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Why not just limit the stock one?
    DauntlessSB92 likes this.
  10. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    I jumped the gun here. I guess I wasn't paying attention and just made an assumption that I had a stock cannister when I was checking my timing.

    I just bought this car back last week so it has taken me a bit to remember some of the things I've done to it.

    I already have a Crane adjustable vacuum canister and I even have a set of vacuum advance limit bushings that Ken (Techg8) of Everyday Performance made a few years ago.

    So I'll just go back to the beginning with my adjustments and see where my issue lies. It may be that I just have too much mechanical advance rather than a vacuum advance issue.

    I have about 8* initial right now and 34* total at around 2200rpm. That is with vacuum advance disconnected of course.

    I am going to try another timing light too. This Innova digital one I have seems to give odd readings occasionally. I have a Summit light with a plain old dial that has never led me astray, I'll break that out to double check.

    FLGS400 likes this.
  11. RoseBud68

    RoseBud68 Well-Known Member

    What's the deal with that fan shroud?
  12. FLGS400

    FLGS400 Gold Level Contributor

    RoseBud68 likes this.
  13. DauntlessSB92

    DauntlessSB92 Addicted to Buick

    The fan shroud is a reproduction part from CARS. It doesn't fit perfect but since originals are unobtainium this will have to do. ( https://www.oldbuickparts.com/product_info.php?cPath=22_445_478&products_id=8864 )

    67 GS400s with either A/C or heavy duty cooling came with a shroud instead of the finger guard. Since I had some trouble keeping the car cool while cruising I added a fan shroud, an 18" 7 blade clutch fan and had my original radiator recored with a 4 row unit. It has made a huge difference but I may still need to add a TA Performance water pump since temps start to creep up in traffic.

    Looking through my old posts on this car, it seems I was complaining about part throttle pinging before I sold the car in 2019.

    I tried turning the Crane canister 4 turns counter-clockwise and I also thew in the largest limit bushing from Ken's kit. It helped a little, but the pinging is still there, even with a tank full of 93. Initial timing is about 6*, total timing is 32* at 2200rpm. With vacuum advance hooked up, timing peaks 42* @ 2200rpm.

    I think my next step needs to be making sure the balancer hasn't slipped. This should be a low compression 455, so in my mind 32* total timing and 10* of vacuum advance should be well within the safe zone. There is no pinging if I leave the vacuum advance disconnected. With +$5/gallon gas I think I'll spend some more time getting the vacuum advance right.

    I can also try Larry's suggestion of using a stock canister. I'll add a limit bushing to that and can probably reduce my vacuum advance a few more degrees over the Crane unit.
    FLGS400 likes this.
  14. rkammer

    rkammer Gold Level Contributor

    You could also try the Accel adjustable vacuum advance. It’s adjustable thru the open vacuum port from zero to 20 degrees and drops very quickly as vacuum reduces down to 10 hg.
  15. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I get guys telling me all the time how their timing is x amount of degrees at 2200 or another RPM. How do you know it isn't advancing beyond that? That's the whole point of using the lightest springs you can ONLY to set the total advance. It's absolutely imperative that when you set your maximum advance (initial + mechanical), that you know for sure there is NO MORE advance left in the distributor.

    You shouldn't even add the vacuum advance until you have set up the maximum advance and driven the car with no ping. Then tune the vacuum advance and check for part throttle ping.

    What part number distributor are you using?
    69GS430/TKX, FLGS400 and rkammer like this.
  16. 2nd Gen Buick Fan

    2nd Gen Buick Fan Platinum Level Contributor

    Here are some spring part numbers that might be useful if you can't find what you want in a kit.
    69GS430/TKX likes this.
  17. JoGi65

    JoGi65 Member

    Hi guys, and thanks a lot for this tread. I read it from the beginning, but to be save I want to verify my future adjustment.

    I have a complete rebuild 455 from 71, standard cam, and a bit higher compression with 11,5 to 12 bar, in an electra 225 costum with 1:2,73 Differential. So I need the most power at low rpm. Also a Pertronix ignition breaker is installed.
    The car is only for normal driving and not for race.

    At the Moment the adjustment is 8-9° at 600rpm, around 20° at 1500 and before 4000 (not exctly mesurement at the moment) it is at around 32°. All with vacuum of. It looks like it’s not the original Distributor, because it has around 24° and original electra has 20°.
    The last Numbers i can read are ...69047 and above NT.
    My vacuum canister (MS 163 16) ads around 16°. (ported vacuum)

    And I don’t hear the engine “knocking ore rattling” with vacuum added. It stays below 50°, and I drive with Shell V-Power 100 with 100 Octane (Europe).

    My mechanic said I should drive without vacuum. In normal driving I can’t really fell a difference with, ore without vacuum. Where should I feel the difference? (i am no native speaker and to much infos in this tread)

    So what’s your opinion for the right adjustment for this car with this fuel?

    Also 10/34/+10 vacuum?

    34 at which rpm? 2500?

    With, ore without vacuum? Portet ore not?

    Ads – Picture from the centrifugal force adjustment.

    Attached Files:

  18. rkammer

    rkammer Gold Level Contributor

    If your Shell V Power 100 is equivalent to our US 100 octane, I agree with your current settings of 10 deg. initial, 24 deg. centrifugal, and 16 degrees of vacuum as long as the engine doesn't ping on acceleration. although I would probably reduce the vacuum canister to 10 to 12 degrees instead of 16. You can also get an adjustable canister if you want to fine tune the vacuum for maximum economy on the highway. As for the RPM of maximum advance, 4000 is fine if you don't care about maximum performance although you can reduce the advance springs to obtain maximum advance sooner say, 3000 rpm.
    JoGi65 likes this.
  19. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    69GS430/TKX and JoGi65 like this.
  20. JoGi65

    JoGi65 Member

    Thanks both for your information and the link. I will do the stop like in the first post.

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