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ignition timing...all read

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  • #16
    I run an MSD boost timing master....driver adjustable timing from inside the passenger compartment.
    Bez Auto Alchemy

    "Don't believe every internet quote" Abe Lincoln


    • #17
      ya, MSD makes some really high qual products...racers scoop their stuff up...

      "then advance the timing until the engine just "pings" at decent acceleration around 30 mph. Now retard the timing just until the pinging disappears."
      ya, how do you think racers did it before MSD showed up?

      I have a '54 packard that runs like crap @ factory marks (which are never accurate anyway), and I added a full 10* by ear as above and it loves it.
      Remember, a retarded engine runs hot, wastes gas, and lacks full power.

      If any of you ever drove an earlier vintage car such as a Model A where you controlled timing from a lever on the steering column, you'd be right on top of this
      1947 M5 under restoration
      a bunch of non-Stude stuff


      • #18
        I don't see how Setting the timing at idle to best vacuum or by any other method will expose a centrifugal advance that is bound up and preventing Stude's conservative amount of advance from being cranked in at higher rpms.

        Which of these curves could be detected with an idle timing test?

        Heck, there could be NO centrifugal advance at higher rpm, so the engine would be operating with timing fixed at, 10, 12 degrees or whatever and if the engine runs smooth, I might not know it. But the engine sure would.
        Until I make some basic checks to see if all the ignition systems are "by the book" the dynamic timing could be anywhere.

        15 minutes with a dial back timing light, a tach and a pencil and paper and I have a foundation to build on.
        If I want to experiment with different advance curves I need to redo the timing/rpm map to see what really happened with the spring/weight change.

        I think it is safe to say Bill Jenkins and any other tuner knew what his advance curve was, and that his TDC mark was indeed TDC, total timing, and which settings got the best MPH or ET, AND monitored spark plug condition since hearing detonation in a race car can be tough.
        Page 18 of "Grumpy's toys" describes the very early 60s era when Bill Jenkinks was achieving success TUNING factory superstock engines.
        Jenkins considered the factory assembled engine mechanicals close enough, but not the distributor!
        "Jenkins did not go through the engine, as he would with the late 409s, feeling there was not much to be done. The carburetor and distsributor were reworked..."


        • #19
          I never run a distributor that I've been asked to work on unless I pull it and check the ENDPLAY, and the centrifugal weights. Also many have the drive gear and shaft pins bent or broken. Most have more than .060 end play! I get 'em to .010. As the end play varies so does the gear lash and the timing. Since the gears are helical, endplay translates into rotational movement, thus timing fluctuations.
          Last edited by bezhawk; 07-28-2013, 04:21 PM.
          Bez Auto Alchemy

          "Don't believe every internet quote" Abe Lincoln


          • #20
            So, assuming the pinging test was done in high gear, 30 mph is about 1500 rpm.
            Barely detectable detonation may indicate optimum timing has now been determined at 1500 rpm.
            What is the timing at 2500 rpm, and is it optimized? how about 3500 rpm? 4500? Is it even within +/- 2 degrees curve of the admittedly conservative timing the factory chose?


            • #21
              wow so i am to believe there are drivers out there who would not know if they had , erroroneosuly, a fixed advance of 10* ( faulty vac. and faulty centrif. advance mechanisms). Hmm, lets see, the car would not run worth a crap, it would stumble horribly, have no power off the line at all, and barely make it over 15 mph. You would swear the car was running lean as could be. Most engines, properly set, are gonna require a max. plus or minus 30 * of advance at 1500-1800 rpm. You won't get much more than that at higher rpms

              Certainly, ppl are free to not follow Mike Van V's suggestions.
              1947 M5 under restoration
              a bunch of non-Stude stuff


              • #22
                ""Initial timing only applies at idle rpm. As soon at the revs climb at all the spark is sparkin' at initial, plus some centrifugal...""

                This comment is "almost" off the mark "IF" the mechanical is adjusted correctly per my first post..!
                ANY of the adjusted timing areas (initial, vacuum AND mechanical) is working any time the engine is running...and at ALL rpm's.

                That is to say, if you set the timing at idle speed (600 to 1000rpm), initial timing to a total of say......38 degrees, as noted in my original post, the mechanical should be in full, just shortly past this point, and the vacuum will change as the vacuum changes (if connected OR working !) in the intake manifold, so we'll discount it for a second, you will still be running that same 38 degrees at 5000 rpm as you were just above idle...!
                ALL of the mechanical should be in full by about 1,000 to 1,100 rpm. That's just off idle...remember the Model T referance..

                Now throw in the vacuum advance. This can be a can of worms to get the ultimate values. A chassis dyno is the best place to "learn" this..!
                The advance stop within the distributor stops this vacuum advance at a point the designers decided on, many times this is too high and should be limited (easier to do on the delco design..!).
                Then you have the "ported" the "unported" and "no vacuum" to find the best way to go.
                And all three have viable reasons for their use.

                Me..I use the "no vacuum" advance thought. Why, it's simple...period. I don't have easy access to a chassis dyno, and it's much too fussy to truly get the proverbial "handle" on. Way too many variables, and...I don't have to be concerned when the diaphram fails or the can gets a leak in it and you don't find this out for another two years...!!
                And to admit the Jeff sorta notes, I really don't care much for the actual number on my street car. I haven't had a "tight" distributer for MANY, MANY years. Just too much in the way of possibility of getting a bad tank of gas, I can just give the distributor a little twist and go about my way without concern for detionation hurting something. They put it back after some better gas is in the tank.
                And takes two hands to actually turn the dist., it is moderatly tight...!

                And as some have noted...all of the above is dependent on a good working, properly adjusted system....points or electronic.

                Thanks to those with the vote of confidence, and the best to your experimenting/learning.

                My next comment (someday) will be on testing carburetor spacers and what they can do for you.


                P.s. - Gee ttbird, sorry to offend you...but all comments still stand as accurate.
                Last edited by Mike Van Veghten; 07-29-2013, 11:17 AM.


                • #23
                  gee, Mike, why would I be offended? I am on your side.
                  After the beating you just took you are gonna dare talk about carb spacers and ram? You know about them and so do I and so don't the racers....but why open another can of worms and get beat up again?
                  1947 M5 under restoration
                  a bunch of non-Stude stuff


                  • #24
                    Something I didn't see mentioned; Say for example you have a distributor that has a centrifugal range of 20 degrees. It may be that at 600 RPM idle the weights/springs have advanced 1 degree. At 800 RPM idle they might be 3 degrees advanced. If both were set to the same degree setting "at idle" the 600 RPM setting would have a true 19 degrees of centrifugal and the 800 RPM setting would have 17 degrees of true advance. Throw softer springs in the distributor for a "faster" curve and it changes a number of things. The softer springs likely mean the distributor mechanical advance is deeper into a fixed advance limit. Thus, it will have an even more limited total advance is set to "factory" numbers. So, simply RPM at idle changes and spring/weight changes can alter total advance.

                    Thus, it becomes like a dog chasing its tail. The remedy for the softer springs is to live with whatever effect more degrees of initial advance brings (if any), or modify (usually requires filing) the advance so it can travel the additional degrees that were lost. It is a lot of trial end error. And, basically seat of the pants (and ear) evaluation. How fast you let out the clutch (or the stall of your convertor), the RPM of the engine on your "ping test hill," the temperature and humidity etc., etc. are all factors. Initial advance at idle is not really that important regardless of what a factory manual might say. In fact, it can be misleading on the other end where it counts.

                    But to the topic of the post, yes at a minimum I'd do the hill test listening for ping at an RPM the advance should be all the way in. Then advance until ping and back off as stated. This may require an idle adjustment at the carburetor to reset the idle to an effective, livable setting. Full advance, under load is far more critical than initial timing and where you will find your "power."

                    What is SO nice about modern engines is the knock sensor, computer and electronic spark distribution. It automatically allows the engine to run "on the edge" at any given RPM and load. Typically when turbo cars have modifications to increase power it is almost always a more aggressive spark advance - and at times a slight fuel increase. Basically the chip or computer modification remove the safety factor the factory considered and push the limit to detonation. A lot of the 4 cylinder turbo cars often see a 25% + power increase just in the timing changes. The mid 80's Audi 5000 Turbo had 165 HP. The timing modification alone raise it 55HP! Of course they wanted $800 to modify your computer to do it. So as the saying goes, "speed cost money, how fast do you want to go?"

                    Last edited by wittsend; 07-29-2013, 01:15 PM.
                    '64 Lark Type, powered by '85 Corvette L-98 (carburetor), 700R4, - CASO to the Max.


                    • #25
                      "ALL of the mechanical should be in full by about 1,000 to 1,100 rpm."

                      Hi Mike,

                      Is that how your distributor is configured?
                      Is that engine or distributor rpm?


                      Dan T