Power Timing Help

Discussion in 'Buick FAQ' started by jhems17, Dec 26, 2018.

  1. jhems17

    jhems17 Well-Known Member

    Hey Buick Family, hope everyone had a Merry Christmas. Just a little back story, I set my carb to fast idle when cold its been decent, did a Seafoam treatment loved the results but since then the carb has been off, I figured all the varnish was cleaned off and now my tight gummed up passages were now free and sloppy, so time to readjust. So I figured set the carb by setting the Timing as one from the Power Timing Sticky that Larry published.
    I have my Dial Back Timing light, the Innova 3568. After the Seafoam it ran like a champ, but Monday morning it was 45 degrees and the car did not want to start, it usually cranks for a few seconds but this time did not start for like a few minutes. Once started I warmed it up for 10 minutes then drove it. About a mile down the road when coming off a red light I had to turn at 1 MPH for if I gave it more gas it would have died. I took it home.
    Today before I started it I checked the idle mixture screws and they were 3 turns in, I reset them to 1-1/2 and then started it. I warmed it up for 5 minutes, choked behaved properly then I quick stepped the throttle to bring it to idle and it stumbled then died. Now it cranked and cranked and would not start, when I look down the Barrels when I move the throttle 2 gobs of fuel shoot down the barrels. So I finally get it started, I turned all screws all the way in and it is idling at 1150 - 1190 sometimes to 1220 RPM.
    Sorry for all that but I know you guys need all the info. So at that idle air filter off, vacuum advance hose still on ( oh shoot should that be off?) I put the timing light on and I don't see my time. I had to push the + button all the way to 26* to get 0*, but it kept jumping every 6 seconds or less. So I set it to 8* which was 17* on the timing light. Now it read 8* and every 6 seconds max it jumps from 8* to 0* then flickers at 0* then goes back to 8* for the 5-6 seconds then flickers again.
    My question is what could cause this flickering (bad distributor or component)? And what do I need to adjust my screws at? (side note what are their names, the fast/hot idle on passenger side and cold idle on driver?)
    I gladly buy you beers on Tuesday for some answers today. Thanks for the knowledge.
     
  2. jhems17

    jhems17 Well-Known Member

    So I tried to start car and same hard starting issue, once I finally got it running I went to 2000 RPM and had 8* advanced timing, idle was 930 -980 RPM and had 4* advanced timing, At 2500 RPM advance was 14*. Tuned the carb a lil and at 850 -890 RPM idle had 26* advanced timing I was on the 4* mark, at 850 -920 RPM I had 30* at the 0* mark. More adjustments and at 790 - 830 RPM I was at 31* advance at 0* timing mark. Attached air cleaner and TVS hoses had 30* at 0* mark. I cruised it and had quick throttle response, quick acceleration and no bog down from stop, With everything connected idle at around 900 RPM and 29* advance at 0*. How can I get my idle to 600 without it dying, how can I get the timing steady, any other help/ stuff I'm getting from the Power Timing Sticky. Thanks for the help I know is coming.
     
  3. johnriv67

    johnriv67 Well-Known Member

    What is your total mechanical advance? Also do you know what that means?

    This will help pinpoint the exact issue
     
  4. jhems17

    jhems17 Well-Known Member

    I do not. I read the Power Timing Sticky but am still not 100% sure on some things. I thought as I turn the distributor the idle gets better, once it starts to drop down and get crappy that is the end of its advance. If that's the case its 30*. If not, please enlighten me.
     
  5. LARRY70GS

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

    I am not sure what you are trying to accomplish because you are not following correct procedure. My power timing thread is all about setting the total wide open throttle timing. The total WOT timing consists of initial + mechanical. To do that requires disconnecting the vacuum advance and plugging it, and you must use lighter springs in the distributor so that the weights move out to their maximum travel at a manageable RPM. Once you set the total, the initial timing takes care of itself. You can then play with different springs to bring the mechanical advance in at the RPM you desire. After you do that, then reconnect the vacuum advance, and tune that if necessary. Read my Power Timing thread again, it is all in there. Look at the attachments (Word Document) in the first post. The stock distributor for a 1971 455 is 1112077. See if it is still there or has been replaced with another part number.

    Two things, if your timing chain is sloppy, the timing mark will jump around. How long has it been since your carburetor has been rebuilt, and what is the part number on it (should be 7041540). The ethanol fuel can degrade the accelerator pump if it is not been updated to the new materials that are ethanol resistant.
     
  6. jhems17

    jhems17 Well-Known Member

    A typical mechanical-advance curve might start advancing at 1,500 rpm and achieve full advance by 2,600 rpm. If that full advance moves the rotor by 25 crankshaft degrees and our initial timing is set at 10 degrees BTDC, then our total mechanical-advance reading at the harmonic balancer at 2,600 rpm or higher would be 35 degrees (10 initial + 25 mechanical = 35 degrees total). We can adjust this total by either adding or subtracting initial or mechanical advance. Changing the quantity of mechanical advance requires modifications to the slot or by changing the bushing diameter that fits over the pin in the slot. Both of these methods change the physical amount of space the rotor can move.
     
  7. CJay

    CJay Supercar owner Staff Member

    Why is the engine idle so high? Do we have a vacuum leak somewhere? Have you ever put a vacuum gauge on it?
     
  8. LARRY70GS

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

    No such thing as typical, it differs with distributor part numbers. First you have to determine what you have.
     
  9. jhems17

    jhems17 Well-Known Member

    Larry, I'm trying to accomplish what your sticky said. You're right I just need to reread it and take my time. I did eventually plug the vacuum advance and it stopped bouncing around, but I did not change my springs. I gather from the thread plus your response the lighter springs are a must. I will order a kit based on your recommendations from the thread. The distributor is from a later model HEI not original points, and the carb is original I think. I will post numbers soon. The car has over 103,000 miles, I got it one year ago, I just gave it a simple tune up, carb has never been right but I've got it dialed in better than it was. I grew up working on old cars but its been a while.
     
  10. jhems17

    jhems17 Well-Known Member

    Larry, I'm trying to accomplish what your sticky said. You're right I just need to reread it and take my time. I did eventually plug the vacuum advance and it stopped bouncing around, but I did not change my springs. I gather from the thread plus your response the lighter springs are a must. I will order a kit based on your recommendations from the thread. The distributor is from a later model HEI not original points, and the carb is original I think. I will post numbers soon. The car has over 103,000 miles, I got it one year ago, I just gave it a simple tune up, carb has never been right but I've got it dialed in better than it was. I grew up working on old cars but its been a while.
     
  11. LARRY70GS

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

    HEI distributors can have a lot of mechanical advance built in. That limits initial advance. With the lighter springs, you'll be able to measure the total mechanical advance.

    If it isn't the original Q-jet, then it is likely wrong for the engine. Find out the part number.
     
  12. jhems17

    jhems17 Well-Known Member

    That post I sent that said "Typical" was just a web page about mechanical advance. I was referencing it to you guys to see if it held water. This is a pic of my carb I.D. It is not what you said it should be Larry. So is it wrong for this year?, better/ worse?
     

    Attached Files:

  13. jhems17

    jhems17 Well-Known Member

    I see 7043244 LD.
     
  14. jhems17

    jhems17 Well-Known Member

    My idle is high because it dies lower. Either vacuum leak or carb out of adjustment or both.
     
  15. jhems17

    jhems17 Well-Known Member

    From what I read its from a 72, I think I just need to go to basics, re read Larry's sticky and just handle one thing at a time. One last question, set idle/carb first then time, or set time then idle/carb?
     
  16. jhems17

    jhems17 Well-Known Member

    I truly appreciate all of you. Thank you.
     
  17. LARRY70GS

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

    7043244 is a 1973 350 carburetor. The idle system on that carburetor is wrong for a 455. That may in fact be part of the problem.
     
  18. johnriv67

    johnriv67 Well-Known Member

    Time first, carb second, then desired idle speed. The first two should get you pretty close anyhow.
     
  19. Briz

    Briz Founders Club Member

    Something that sudden sounds like sloppy chain and or a vac leak.
     
  20. jhems17

    jhems17 Well-Known Member

    Dang man I think I bought a lemon. Not necessarily since I love Boat-tails but thought had an OG engine. So he changed the distributor, changed the carb (why would you down grade if you tow?) was he a dumbass? Well now I have to decide what to do. Alright gentleman, thank you very much, I will do what you advised and anything else, then report back.
     

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