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| Joined: | 05-01-2005 |
| Location: | Minneapolis, Minnesota USA |
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Determined TDC by aligning intake & exhaust cams to their marks, removed dizzy cap rotor points to #1 plug and crank pulley timing mark lines with TDC.Steve,
In total, that's correct. But you backed into it, and the good result is more due to luck than proper procedure. Just to make a point, and to get your head focused, TDC is all about CRANK position. The first step should be to rotate the crank until the mark on the V-belt pulley aligns with the 0° (TDC) timing mark. Only then, look at the cam pulleys.
If the pulley dots are on the imaginary centerline between cams, but on far opposite sides of the pulleys, then the crank is 180° out, and the #4 cylinder is at TDC. Rotate the crank through another full revolution and back to TDC. That should bring the timing dots half way around the cam pulleys, adjacent to one another, and aligned on the imaginary centerline between the cams. Now the #1 cylinder is at TDC, and you're ready to move on to the ignition timing.
The pulleys can only be indexed on the belt in whole tooth increments. One tooth pitch is the distance from a point on one tooth to the exact same point on the next, adjacent tooth. In other words, the total of one tooth width plus one gap width... much more than just the width of one tooth. IF the pulley timing dots are misaligned by just a little bit, far less than a full tooth + gap, then that's just due to tolerances. At TDC, and a 'little bit' off the centerline between the pulleys, they're aligned as close as they're going to get with OEM non-adjustable pulleys, and there's nothing more you can do about it. Relax.
Cam timing is defined as "AT TOP DEAD CENTER", so no, it is not permissible to nudge the crank a little off TDC in order to bring the cam pulley timing marks into perfect alignment. With the #1 cylinder AT TDC, the cam pulley dots are where they are... you don't get to move the crank off TDC to "fix" cam timing !
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Now move your attention to the distributor. With the cap on, observe the positions of the plug wire terminals such that you can imagine the locations after the cap is removed. Now remove the cap and notice the rotor's location. With the crank at TDC (all that discussion above), the terminal the rotor is pointing toward is now #1. Reinstall the cap to identify the relevant terminal, and mark it as #1.
As you look at the terminal end of the cap (viewed from the flywheel end of the engine looking forward at the distributor cap), the rest of the terminals should be marked in 1-3-4-2 order, COUNTER-clockwise around the cap. Now make certain the wires from the spark plugs are installed on the correct terminals. The #1 spark plug is closest to the front of the engine.
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Rotate the crank through just short of two full revolutions, stopping with the timing mark on the V-belt pulley at your desired ignition static advance. If you want the Static Advance to be 10° BTDC, then stop the crank at the 10° BTDC timing mark.
Back at the distributor -- The rotor's arm ends with a flat, wide brass blade. The leading edge of the rotor's blade (it rotates counter-clockwise) should now be aligned with the cap's #1 terminal location. At this point, over-lapping a little is better than an air gap. If that's not the case, then loosen the distributor and rotate it as required to bring the #1 terminal in to alignment with (slightly overlapping) the rotor's leading edge. Re-tighten the distributor clamp.
NOTE: The distributor is spring-loaded outward. If you simply loosen the clamp, the distributor will pop out of the oil pump. First, grasp the distributor with your left hand and apply inward pressure. Hold that inward pressure while you loosen, rotate, and tighten the distributor. Don't release that inward pressure until the clamp is tight again.
The engine part of the equation is now set. However...
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The Pertronix amplifier unit doesn't mount in "ONE" indexed position in the distributor. The screw hole is a slot, and the amplifier can slide back and forth before being tightened down. If the amplifier is at the counter-clockwise (left) extreme, the spark will fire late. If it's at the clockwise (right) extreme, the spark will fire early. 'Perfection' is 1) the crank reaching the Static Advance timing mark (10° BTDC, or whatever your target is) at the same time that 2) the rotor's leading edge aligns with the #1 terminal, and 3) the amplifier fires a spark.
That last one, item 3) above, is a matter of where the amplifier is in it's mounting slot when the screw is tightened down. To far to the right (clockwise), and it might fire the spark before the rotor is aligned with the cap's terminal. Too far to the left (counter-clockwise), and it might fire the spark late, well after the rotor has reached the terminal, and result in retarded ignition timing despite the crank being correctly set to 10° BTDC.
With the crank set at your target timing advance, and the distributor rotated to bring the terminal into alignment with the rotor's leading edge (or slightly over-lapping), loosen and re-position the Pertronix amplifier's pick-up to be aligned with the moving reluctor as best you can. Pertronix refers to that adjustment as "Phasing". All the engine adjustments are "ignition timing", and the amplifier adjustment is "Phasing". And they need to agree.
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The spark isn't instantaneous, is has a duration. By aligning the plug wire terminal with the leading edge of the wide rotor blade, you're giving the spark the maximum amount of time from when the rotor's leading edge first aligns with the terminal, to when it's trailing edge departs. At 7000 rpm, the time required for the full width of the blade to sweep by the terminal is still very brief.
Phase the Pertronix too far to the right (clockwise), and it it might fire the spark before the rotor aligns with the #1 terminal. That's a lost spark, and nothing happens.
Phase it too far to the left (counter-clockwise), and it may fire the spark late, after part of the rotor's width has partially passed the terminal. The spark will still reach the terminal, and the plug will fire, but you have given up some of that all ready very brief duration time for the spark. At high rpm, the trailing edge of the rotor may leave the terminal before the spark is done. The spark will reach the sparkplug, and the engine will run, so this is the lesser of two evils. But the goal is to Phase the amplifier as best you can to take full advantage of the spark's full duration.
flatlanderep wrote:
Is it possible the distributor is not seated all the way in the housing?Possible, and you should make certain it is seated. But the drive dog is engaged or it's not. There's no 'out a little' that will affect timing. Grab the rotor and try to spin it.
If the rotor turns freely, then the distributor is partially disengaged to the point that the drive dog is not in the mating slot in the end of the Auxilliary Shaft. If the rotor is 'solid', and doesn't turn at all, then the drive dog is seated in the Aux Shaft's slot. It's either/ or, and not something that 'slightly' affects ignition timing.
Regards,
Tim Engel
Last edited on 11-06-2019 03:53 pm by Esprit2