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

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.

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.

I would suggest starting a new thread so we can better help you.

Yes, I agree. One that isn't six years old already.please be sure to put it in the tech section, thank you.

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.

There, debate over.

aotrucker said:

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.

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your balancer is probably FUBAR

My distributor can never be off a tooth.

Wait.......

Oh yeah, I don't have a distributor.

You other guys,...,......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...

It's a new balancer

addermk2 said:

your balancer is probably FUBAR

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Stop that,..we are trying to get him to start his own thread,...not give life to Imhotep.

I have my own thread about it

aotrucker said:

I have my own thread about it

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Outstanding.

Now we can return Ramsses back to his tomb.

madmike1157 said:

Stop that,..we are trying to get him to start his own thread,...not give life to Imhotep.

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madmike1157 said:

Outstanding.

Now we can return Ramsses back to his tomb.

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pot.... kettlle...

addermk2 said:

pot.... kettlle...

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Quiet. I was answering his comment from today, as it applies to today. You were making a comment as it applied to a long dead topic recently revived today.

See the difference?

madmike1157 said:

Quiet. I was answering his comment from today, as it applies to today. You were making a comment as it applied to a long dead topic recently revived today.

See the difference?

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no.... pretty sure i quoted, and replied to his post from today.

addermk2 said:

no.... pretty sure i quoted, and replied to his post from today.

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But his post lived in the middle of a mummified thread.:zombie:

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

99FiveOh said:

the car wouldn't know or give a crap

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If I did it, I will know and I will be driven madly insane by it unless I correct it.

I think they are referring to the vehicles that have a fixed mounting point on the distributor that makes it not adjustable. Some examples of vehicles with non-adjustable distributors include classic cars like the Ford Model T, Chevrolet Bel Air, Volkswagen Beetle, and older trucks like the Ford F-Series from the mid-20th century. These vehicles typically relied on mechanical distributors for ignition timing and didn't have the electronic controls found in modern vehicles.The saying that the distributor must be "off a tooth" originated from the era of mechanical distributors, where precise timing adjustment was crucial for engine performance. In vehicles with non-adjustable distributors, fine-tuning ignition timing required physically altering the position of the distributor itself. If the timing was slightly off, mechanics might move the distributor by a small amount, often colloquially referred to as being "off a tooth," to achieve the correct timing alignment. This practice became common among mechanics working on older vehicles with non-adjustable distributors. That saying about the distributor being "off a tooth"? Well, it's one of those quirky phrases that an old-timer probably tossed out one day while tinkering under the hood, and somehow it stuck around. Picture this: a seasoned mechanic, grease on his hands and a twinkle in his eye, imparting wisdom to the younger folks with a dash of humor. It became a sort of inside joke among mechanics, a nod to the days of tinkering with non-adjustable distributors and the occasional need for a bit of finesse to get things just right. Sometimes, the best advice comes with a side of humor and a touch of nostalgia.

madspeed said:

Thx @dnbonds

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