Can a distributor REALLY be one tooth off? lets discuss this...

If we didn't have an upper intake, you would just stab the dizzy wherever the hell you wanted and spin it til it starts and set it to 10 degrees and call it a day.


The only reason we pay any attention to where we stab it is to make sure we have enough adjustment range to go from, say, 8-16 degrees without hitting the intake manifold.
 
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The “one tooth off fable”

Before installing the distributor, you need to insure that #1 cylinder is on compression stroke when you put the distributor back in place.


When the spark is right, the injector timing is right.
On a 5.0 EFI Mustang you can't get the distributor installed far enough to cause problems if the rotor is pointed at the stock #1 position on the distributor cap. The TFI module will either run into the radiator hose outlet on the intake manifold or the A/C compressor when you set the timing with a timing light.

The exception to this statement is that if you install the distributor so far off that you can no longer get the rotor to point at the #1 position on the distributor cap. If you move the spark plug wires so that the rotor points to the revised #1 spark plug position, this will throw the injector timing off.

The ignition timing signal and the injector timing are triggered by the same mechanism: the distributor PIP pulse. There is a fixed relationship between the two; you can't change one without changing the other. The PIP shutter wheel does have the #1 slot wider than the other slots and this tells the computer where the firing order starts. The shutter wheel #1 slot does not move or change position, no matter how you rotate the distributor: it is fixed in relation to the distributor rotor. That allows the computer to know when to start the sequence to pulse the injectors so that they spray only when their intake valve is open.

A 4 cycle, 5 event engine takes two turns of the crank to complete a power cycle that has a duration of 720* (*=degrees). In our theoretical engine, each of the 4 cycles is separated by 180*.

At 0* TDC (Top Dead Center), both intake and exhaust valves are closed. The spark plug fires or has fired, and the expanding gases force the piston downward.

At 180* later, BDC (Bottom Dead Center), the exhaust valve starts to open and the piston starts upward towards TDC, forcing the spent gases out the exhaust valve.

At 360*, TDC, the exhaust valve closes and the intake valve opens and the piston starts downward and the resulting vacuum pulls the air into the cylinder. Since this is Sequential EFI, the injector starts to spray fuel into the port. The start and stop of the injector spray (injector duty cycle) is calculated by the computer to deliver the right amount of fuel according the sensor inputs.

At 540* BDC, the intake valve closes, if the fuel injector was spraying, it stops spraying. The piston starts upward on the compression stroke, compressing the air/fuel charge.

At 720* TDC, the cycle starts all over again with the firing of the spark plug.

Note that in real life, the events of ignition, exhaust, intake, fuel injection, and compression will not start on 180* boundaries, but will vary slightly to change the performance characteristics of the engine.
 
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What some people fail to realize is that the rotor and reluctor wheel share the same shaft, so you can't have proper ignition timing without also having proper injector timing. It could be off IF the rotor could be installed in a different position but you can't do that so there's no way to be a tooth off.
 
I am having a problem with my timing. I installed a trick flow top end kit on my 92. Why am I having to run it at 38° to make run most of the way normal? Mind you it still needs a good dyno tune.
 
Since this thread is now dredged up and brought to the surface from the depths of anonymity, near dead, where only the most persistent of searches could resurrect it stinking and rotting but now with faint new life breathed into it, allow me to respond to the original debate.

Yes the distributor can be off a tooth. Or several. Yes you may make it work in the incorrect orientation, but it is wrong. The anal retentive perfectionist me could never accept a distributor that was cocked off the correct orientation to make it run, plug wires stretched like bow strings to reach their misaligned terminals. As an apprentice technician, I would have received a failing mark if I had tried to pass off a distributor installed at any orientation other than stock. As a professional, I could not foist such shoddy work onto the next poor fellow to have to work with or spend time correcting. It is just wrong and you should aim for a higher standard in your work. :nono:

There, debate over. :D
 
Since this thread is now dredged up and brought to the surface from the depths of anonymity, near dead, where only the most persistent of searches could resurrect it stinking and rotting but now with faint new life breathed into it, allow me to respond to the original debate.

Yes the distributor can be off a tooth. Or several. Yes you may make it work in the incorrect orientation, but it is wrong. The anal retentive perfectionist me could never accept a distributor that was cocked off the correct orientation to make it run, plug wires stretched like bow strings to reach their misaligned terminals. As an apprentice technician, I would have received a failing mark if I had tried to pass off a distributor installed at any orientation other than stock. As a professional, I could not foist such shoddy work onto the next poor fellow to have to work with or spend time correcting. It is just wrong and you should aim for a higher standard in your work. :nono:

There, debate over. :D

It can be a tooth off from a cosmetic point of view but the car wouldn't know or give a crap since the body of the distributor is properly oriented with the rotor/reluctor wheel.
 
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My distributor can never be off a tooth.

Wait.......:thinking:

Oh yeah, I don't have a distributor.

You other guys,...:nonono:,......Didnt Henry use one of those things on the model T?

You all probably still listen to Ratt or Quiet Riot on your Pioneer Super Tuner 3 cassette players.........

It's 2016,...the least you could do is swap over to EDIS,

Wait,..... Even that is already a decade old technology. Skip that.

Get antique plates instead.

Crotchety is as crotchety does...
 
no.... pretty sure i quoted, and replied to his post from today.
But his post lived in the middle of a mummified thread.:zombie:
zombie-mummy.gif

Aww never mind,....I got two guys that I'm yankin chains now, this is taxing my creativity
 
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