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Ignition timing for olde time automobilists?

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  • Ignition timing for olde time automobilists?

    OK, the vehicle is a 1928/9 6 cylinder Dodge sedan which has overheating problems under some conditions.

    The engine does not overheat pulling up hills, it does overheat when running freely on the flat.

    Engine head gasket checked, water pump checked, new radiator ($$$!), fan/pump belt checked.

    The owner says the engine never pinks(pings) but according to my recollection of such vehicles it should pink when under unnatural load such as opening the throttle wide in top gear when it should really be in a lower gear. He always drives with the ignition advance control fully advanced.

    I suspect the ignition is too retarded and that causes the overheating....comments?

    Anyone old enough to remember such things?

    Thanks

    John

  • #2
    Different car, but I had a '19 Ford T Touring that exhibited a similar symptom. It wouldn't heat quite enough to boil. Turns out that cracking the throttle a bit with the butterfly screw let enough extra air through to stop the issue. Then adjusted the timing and mixture to bring the idle back down. Problem solved!

    Weird....

    Pinging should be prevented whenever possible as it can damage piston/valves. Like your Dodge, the advance needs to be adjusted to the immediate conditions for best operation.

    Pete
    1973 SB 10K .
    BenchMaster mill.

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    • #3
      I certainly remember. My Land Cruiser had what to me was an unusual vacuum retard system. Probably more related to the crude emissions controls that were just being mandated. Otherwise, engines had vacuum advance.

      In your friends case, perhaps some experimenting would be in order, rather than just 'full advance' all the time. Perhaps also there's a misadjustment in the positioning of the distributor that actually requires that the advance control be set to full advance. Seems to me there should be a 'sweet spot' for that setting which would put it more towards the middle of its range. Then you'd have a bit more advance available- if as you say it seems too retarded now, that could help. Just guessing, I'm not a certified mechanic.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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      • #4
        I am presuming that it has no auto adjust, and the control is "it".

        And I seem to recall that the engine can overheat from advance as well as retard, but that it takes a good bit of advance to do it. Does the control have the right RANGE? If it is shifted wrongly, it might never be able to be correctly adjusted.

        Also, mixture might affect timing. Lean seems to slow the flame, so if it is lean, it might never "pink" (actually a great word for it, really), and lean can cause overheating.

        With it lean, an all-the-time advance might bring it back to working kinda-sorta reasonably, but it would be compensating errors.

        If the carb is over-rich when floored, then it might not "pink" on hills, due to rich mix.

        Seems like a case where starting at the basics and going right through the tuneup might be justified.
        1601

        Keep eye on ball.
        Hashim Khan

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        • #5
          Originally posted by The Artful Bodger View Post
          ..................
          ...................
          I suspect the ignition is too retarded and that causes the overheating....comments?

          .....................

          John
          I suspect you may be correct. Retarded ignition timing can be a contributing factor to overheating. This in conjunction to a lean part throttle fuel/air mixture will will result in a delayed burn that is still well into the burn process going out thru the exhaust port and thus leading to increased heat input to the coolant. Full throttle application like under a heavy load would place the carburetor's main fuel circuit into play thus increasing the fuel to air ratio and fattening up the mixture to help mask the somewhat retarded timing's affect on overheating.

          It would be ideal if the timing could be increased to the point of detonation (audible pinging) and than retarded to the point that it was no longer present. Try it there to see if the condition persists. Check also for carb jetting and intake/vacuum leaks as these are also contributors to the overheating situation.

          I'm sure this this is strictly a manual timing control without the benefit of centrifugal or vacuum advance so it should be easy to change settings in order to find the sweet spot.
          Home, down in the valley behind the Red Angus
          Bad Decisions Make Good Stories​

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          • #6
            I should have added that this is one of the vacuum advance units main benefits. It not only retards timing under load due to little to no vacuum signal, but it also advances the preset or centrifugal timing significantly under light load or part throttle conditions thus increasing fuel mileage considerably while reducing engine temperature input due to compromised (retarded) mechanical timing.
            Home, down in the valley behind the Red Angus
            Bad Decisions Make Good Stories​

            Comment


            • #7
              I have not taken a good look at the distributor yet but I expect it has a simple centrifugal advance mechanism and it almost certainly will not have vacuum advance.

              Meanwhile the owner has managed to borrow a few bits to swap in including another radiator, pump and fan. It will be interesting to see what results if any.

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              • #8
                I would have gone with 1, thermostat stuck, 2, v absent 3 belt slipping 4 pump 5 too many radiator leak fix things, blocked cores in the radiator
                The above have been the usual suspects so far with the exception of one head gasket, exhaust gasses getting into water ways caused an air lock type of thing stopping circulation, top hose was hot and stunk when removed
                Very remote that ignition was to blame, it's usually the easy things first, took one pump off recently the impeller was eaten away
                Mark

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                • #9
                  This may or may not be pertinate-----
                  I had an overheat problem with my air cooled 180 HP four cylinder aircraft engine.
                  The cylinder head temperatures would rise to above 425 DF when in normal level cruse power.
                  That's too high!
                  The engine has a dual electronic ignition system that has a complex advance curve.
                  The solution was to RETARD the spark system trigger by 3 degrees.
                  The cylinder head temperatures dropped to under 400 DF and became very balanced.
                  I am sure that the max takeoff power dropped slightly but it was unnoticeable.
                  Problem solved.
                  Bill
                  Last edited by Seastar; 12-24-2017, 10:25 AM.
                  I cut it off twice and it's still too short!

                  Comment


                  • #10
                    Originally posted by The Artful Bodger View Post
                    OK, the vehicle is a 1928/9 6 cylinder Dodge sedan which has overheating problems under some conditions.

                    The engine does not overheat pulling up hills, it does overheat when running freely on the flat.
                    He always drives with the ignition advance control fully advanced.

                    I suspect the ignition is too retarded and that causes the overheating....comments?
                    First, make sure the radiator is not rusted or calcified up inside (by using well water which has minerals in it that deposit inside) so that you do not have proper coolant flow and heat transfer. Also make sure there are no leaves or other debris plugging up the air passages through the fins. And if this old car uses a thermostat, make sure it is installed and working properly.

                    Otherwise, from everything I ever knew about cars, ignition timing that is too far advanced is what will cause a car to overheat - NOT retarded timing. It also destroys pistons, rings and valves due to the extremely high pressures and temperatures involved with pre-ignition. You appear to confirm this by saying the owner always ran it "fully advanced" - but then you illogically conclude it's retarded. Why?

                    First thing I'd do is remove the distributor cap (unless it has a magneto ignition) and remove the spark plug from the number 1 cylinder. Verify that the ignition rotor (inside the dist cap) is pointing to the number 1 cylinder plug wire when the number 1 piston is at top dead center (make sure the points are opened as well to ensure you are on the firing stroke). Actually this is probably a flathead engine, so you may not be able to see the piston at TDC (or detect it using a narrow screwdriver dropped down inside). But you should be able to use a compression meter to detect compression as the rotor approaches the number 1 plug wire. The point of all this is to ensure the distributor has not been installed one gear tooth off and then rotated heavily into either a very retarded or advanced position to achieve basic firing timing again.

                    If you have a timing light, try checking the timing according to whatever the manual says. Although timing lights may not have existed back in the 1920's (I dunno). So I would put the number 1 cylinder at TDC, use a piece of chalk to put a mark on the flywheel or harmonic balancer or pulley (whatever it has) and also a mark on a stationary piece of something next to it (both chalk marks should be aligned. Rotate the engine back below top dead center (BTDC) about 4 degrees put another mark on the pulley and then again at 8 degrees BTDC. Then fire the engine up and see what the timing light measures. Most engines at idle run at about 2-4 degrees before TDC and advance up to about 8 degree BTDC at high engine speed. You can set it at 4 deg BTDC and take it for a spin. If it doesn't ping, advance a little bit at a time until it does ping...then back off a little. That's the old school way of setting timing. Although this car is so old it may have a manual ignition timing control on the steering column. In that case set the timing at 4 deg BTDC or 0 deg/TDC with the control in the centered position, and then experiment with different settings while driving around.

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                    • #11
                      I didn't read all the suggestions so sorry if this was mentioned. The lower radiator hose should have a spring in it to prevent it from sucking shut (collapsing). If the spring rusted out or moved that can cause it

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                      • #12
                        Thanks for all the comments.

                        It will be a few days before we can get back on to this project.

                        Comment


                        • #13
                          Originally posted by Machine View Post
                          First, make sure the radiator is not rusted or calcified up inside (by using well water which has minerals in it that deposit inside) so that you do not have proper coolant flow and heat transfer. Also make sure there are no leaves or other debris plugging up the air passages through the fins. And if this old car uses a thermostat, make sure it is installed and working properly.
                          New radiator, no thermostat..


                          Otherwise, from everything I ever knew about cars, ignition timing that is too far advanced is what will cause a car to overheat - NOT retarded timing. It also destroys pistons, rings and valves due to the extremely high pressures and temperatures involved with pre-ignition. You appear to confirm this by saying the owner always ran it "fully advanced" - but then you illogically conclude it's retarded. Why?
                          If the ignition is over advanced I would expect it to pink under light loads but it does not. If the ignition timing is correct (and if my memory serves me right) the engine would pink when overloaded as in trying to accelerate in too high a gear, but the engine never pinks even though the owner keep the control fully advanced.


                          If it doesn't ping, advance a little bit at a time until it does ping...then back off a little. That's the old school way of setting timing. Although this car is so old it may have a manual ignition timing control on the steering column. In that case set the timing at 4 deg BTDC or 0 deg/TDC with the control in the centered position, and then experiment with different settings while driving around.
                          Yes, this car has manual ignition control.

                          Comment


                          • #14
                            In your part of the world do you have the dreaded ethanol added to the fuel ? It keeps the tree huggers happy but it buggers up the running of most old engines. On my late 1920s motorcycle engine I have made carburettor slides with differing cutaways to richen things up and retarded the ignition 4 degrees when on full advance. I marked the engine up accurately with a degree disc made marks for full advance at 35 instead of 39 degrees. Not running perfectly yet (will it ever?) but going in the right direction, when checking plug colour it now looks more like it should. It is definitely running cooler than before.

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                            • #15
                              I do not believe we have ethanol in the fuel but I do wonder how petrol has changed over the last 80+ years.

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