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Spark Timing, Set It and Forget It

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  • Spark Timing, Set It and Forget It

    There are at least a couple ways to set the timing. You first must set the point gap, and I always set mine to .020" with the points setting on the highest part of the cam lobe. This remains the same whether you use the "A" cam or "B" cam. After the points gap is set, you can then push the spark lever all the way up, which is where it should always be when starting the engine. Now you can hand crank the engine until you just feel the timing pin drop into the cam gear detent. The engine is now on top dead center and ready to fire #1 spark plug. If the points aren't just starting to open, you must loosen the cam screw and rotate the cam until the rotor points to #1 contact and the points are just ready to open. I like to use the correct cam tool to hold the cam in position as I tighten the screw.

    If you like to use a test light to see when the points open, rather than just your eyes, then connect the clip to the red wire terminal on the coil, and ground the test light point to a head nut or other good ground. Now, when the points open, the test light will light up. If you go past the dimple in the cam gear, then just hand crank the engine almost two more revolutions to bring the cam dimple back around. If you put the tranny in high gear and push the car backwards to bring the dimple back into position, be sure to go back past the dimple, then hand crank slowly until the timing pin drops in, and stop. When you go backwards, you need to go past the mark and then turn it forward again to make sure all the freeplay is on the leading side of the cam.

    Double check the freeplay by lightly trying to turn the distributor rotor clockwise, and it should not move. The rotor turns CCW, so you want any freeplay taken up as you check the timing.
    Try turning the rotor counter clockwise and it should move to take up the freeplay. This will also let you know how worn the shaft tangs are.

    Also be sure the timing lever on the steering wheel will move the distributor upper plate arm from one side of the opening to the other side as you move the lever up and down. If it doesn't, then something will need to be adjusted. On the 2 tooth steering, the column can be rotated to help bring this into correct adjustment.

    Another way to set the timing is even easier, and I learned this method from Marco, the man with the Model A knowledge. When you hand crank the engine until the timing pin drops into place, the rotor should be pointing towards the right headlamp and in exactly the position as shown in my picture. With this method, you don't have to worry about where the spark lever happens to be. This will get you as close as you need to be for timing the points to open at TDC. Of course, once again, be sure the points are set to .020" and again this is the same whether you use an "A" cam or a "B" distributor cam.

    Be sure to use distributor cam lube on the rubbing block, and a drop of oil on the pivot pin. Also be sure to fill the distributor lube cup with oil about every 500 miles. You can't over lube the distributor and extra oil won't mess up anything.

    The spark lever should move the timing from TDC all the way up to 40 degrees BTDC, which I feel is too much advance. I never run more than about 30* on a stock engine, and an engine with higher compression will use even less advance because the flame spreads quicker with higher compression, so the peak pressure occurs sooner in the piston movement. You want peak pressure shortly after TDC, and not before. Too much advance can damage babbit, rods, and pistons.

    If the timing is too late, you can overheat the engine have loss of power.

    I'll also show a picture of the correct camshaft gear timing, as some books in the past have shown it in the wrong position. This must be right before you even worry about getting the spark timing right. The cam gear timing mark lines up to the RIGHT side of the keyway, not the left as incorrectly shown in some books.

    Once the timing is set, you just occasionally reset the points to .020", but don't have to mess with the timing again. Set it once and forget it. The only time you have to recheck the timing is if you loosen or remove the distributor cam.

  • #2
    Electricity 101

    When making electrical checks you can be measuring voltage or amperage. Voltage is the pressure behind the electron flow. Think of a high pressure hose squirting water on the lawn. It might have 40 pounds of line pressure, but not a lot of flow. Amperage is the amount of flow. Think of a river which flows hundreds of gallons of water per second. It doesn't have much pressure, as you can hold the open end of a low pressure gauge against the flow, and the needle won't move.
    It takes pressure to move the electrons, such as thousands of volts to make the electrons jump the gap of the spark plug, but it takes current flow (amperage) to do the work. Think of the high amperage needed to spin starter armature to turn the engine over.

    When you do electrical checks for voltage loss, you need to have current flow, or at least try to have current flow. A very poor connection can show the right voltage, but it won't flow the current. If every wire except one is broken in the starter cable, you can still measure the correct 6.3 volts at the starter switch, but it won't flow the current needed to run the starter. If the starter spins fine, then you can assume the battery connections and ground strap are fine, so if you are trouble shooting for poor lighting, horn, or ignition, you can start at the starter switch and move upstream towards the part that isn't working.

    Remember, you need current flow or at least trying to flow current to make these checks, so if the lights don't work, turn them on and measure the voltage at the starter switch. If it's good then move up to the terminal box and check each wing nut. If both are good, then you know the terminals, wires, and ammeter are OK, so you move on to the cutout, where the lights harness picks up it's power. If you have good voltage there, move to the light switch, and from there to the headlamp sockets. If you still have good voltage at the headlamp sockets, then you could have a poor ground. Use a clip lead as a good ground bypass.

    It only takes seconds to check voltage along these points. It's always a good idea to carry a couple of 36" clip leads to fix a poor connection while on a trip. The clip leads are also handy to use as a temporary bypass for a good ground. Be sure the clip leads are good quality with soldered wires at both ends. I wasted a lot of time once making checks and wondering why things weren't making sense. It turned out my cheap clip lead wasn't making a good connection because the wire wasn't soldered. Another time I was left wondering why things weren't making sense, and found my multimeter had a loose connection inside the case, where the leads plug in.

    With electricity, if you have more than one problem at the same time in the same circuit, then it can really get confusing trying to make sense out of it.
    In the end, just carry a good test light, and a good analog multimeter, plus a wiring schematic of your car, and it won't take long to find the problem.

    BTW, when you see someone walking around checking batteries at a junkyard by using just a voltmeter, they can't really don't know much about the battery.
    The correct battery tester puts a load on the battery as the meter checks the voltage. This is the only way to know how good the battery is.

    Comment


    • #3
      Tom
      thanks for writing and sharing these two excellent how to tutorials on setting the timing and basic electricity.
      these articles are both saved separately in the tech forum for future easy to find reference.
      3 ~ Tudor's
      Henry Ford said
      "It's all nuts and bolts"


      Mitch's Auto Service ctr

      Comment


      • #4
        Tom, what's with the screws in the rotor arm?
        Bill
        http://www.brauchauto.com/
        Eastern Connecticut

        Comment


        • #5
          Originally posted by 2manycars View Post
          Tom, what's with the screws in the rotor arm?
          I like to balance my rotors. It not only takes the side load (except points arm spring pressure) off the bushings, but it will eliminate uneven points opening when bushing clearance gets to be more than .001". With the stock rotor, the heavy side is the brass arm, and this will be slung outward, so when the brass is towards the points rubbing block, the points will be opened wider if the bushing has wear, and likewise the points gap will be less when the brass is opposite the rubbing block.

          The crankshaft should have counterweights for the same reason.

          Comment


          • #6
            Great papers Tom, thank you!

            Comment

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