Timing retarding 2* after installing crank trigger

[colormebad]

Originally Posted by pmrphil

The timing chain has nothing to do with timing when using a crank trigger, only affects the position of the rotor. I just adjusted for it so it was correct at RPM. Sure does make you wonder, huh?

That's what 2 MSD techs told me... Its hard for me to 100% believe but I will find out one way or another... Its down to this bracket needing to be bolted to the motor instead of the motor plate, and with a new bracket, or the balancer...

[colormebad]

Originally Posted by 1968 SS

Normal operation of MSD 7AL-3 ignition box to retard timming up to 4*
Set timming at 3,000 RPM as per MSD instructions.

Brian
.

Tech just told me a few days ago, set it where I want it and it should not retard .... Did the same thing with a brand new digital 7

[FED 387]

SORRY -- missed that part about the trigger was just looking at the pointer and timing mark---FED 387 You are correct

[Ron Finney]

The statement that the distributor has nothing to do with the timing when using a crank trigger is ridiculous. How do you think the spark gets to the plug wires??? oh yeah, that is also where the timing light gets it trigger..... It is correct that the point of the crank trigger is to get an accurate timing signal by taking the timing chain variation out of the equation. However, that is only the pickup side of the equation. Unless you are using DIS, the distributor is still in the equation and it is driven by the timing chain which does have slack and does stretch. Every chain driven engine will have 1-2 degrees of slack which will retard the timing...if it gets much more than 3-4 then time for a new chain. That is why MSD is telling you to time the motor at 3000 or more, you have the slack out of the chain at that point. Your vibrating bracket doesn't sound good either, but I think you are trying to fix normal operation if you are looking at timing in an unloaded (idle) to loaded (high RPM) comparison.

[pmrphil]

Originally Posted by Ron Finney

The statement that the distributor has nothing to do with the timing when using a crank trigger is ridiculous. How do you think the spark gets to the plug wires??? oh yeah, that is also where the timing light gets it trigger..... It is correct that the point of the crank trigger is to get an accurate timing signal by taking the timing chain variation out of the equation. However, that is only the pickup side of the equation. Unless you are using DIS, the distributor is still in the equation and it is driven by the timing chain which does have slack and does stretch. Every chain driven engine will have 1-2 degrees of slack which will retard the timing...if it gets much more than 3-4 then time for a new chain. That is why MSD is telling you to time the motor at 3000 or more, you have the slack out of the chain at that point. Your vibrating bracket doesn't sound good either, but I think you are trying to fix normal operation if you are looking at timing in an unloaded (idle) to loaded (high RPM) comparison.

Try checking your timing and then rotate the distributor a bit (either direction) and you will see that timing doesn't change (if you're using a crank trigger) the only thing that changes is the position of the rotor in relation to the plug wire tower in the cap. It has no effect on timing events until you turn the dist so far that the spark is transferred to an adjacent tower. The spark is signalled by the trigger, not the dist.

[Ron Finney]

Originally Posted by pmrphil

Try checking your timing and then rotate the distributor a bit (either direction) and you will see that timing doesn't change (if you're using a crank trigger) the only thing that changes is the position of the rotor in relation to the plug wire tower in the cap. It has no effect on timing events until you turn the dist so far that the spark is transferred to an adjacent tower. The spark is signalled by the trigger, not the dist.

Your observations are correct, but your conclusions are incorrect. The spark (ie. coil) is being signaled by the crank trigger but the spark generated by the coil is being delivered by the distributor, and the timing light is being triggered by the spark in the wire, not the crank trigger. While the change is small, there is a change. The reason you don't see change with the light is that the spark is jumping the gap to the terminal and with the speed of electricity, and the width of the tab on the rotor you are not going to detect that with the flash of the timing light. But, since the spark is being delivered to the terminal in the cap via the tab on the rotor...if it gets there sooner or later...the timing IS changing.....what you are doing is moving it from the center of terminal slightly, yes it is still firing the light the same, because the spark is still jumping the gap. If you were to move the rotor phasing to the edge of the conductive plane, then try moving the distributor you would find that you start killing the cylinder....the spark would now be getting there to late and the gap is too large for it to jump. Granted, this is extreme, but it will show you that moving the distributor will affect timing. If you were to use a scope rather than a timing light to look at the signals in real time, you would see the timing change as well.