Question on ignition timing

[Mint86720]

So i have a question...the ignition timing is supposed to be set at 5 degrees below tdc in theory if i were to put the timing mark on the harmonic balancer to 5 degrees below tdc and took dist cap off and rotated the dist and lined the rotor up with #1 on the dist cap wouldnt it be dead on?

[Doctor510]

That should read, BTDC: BEFORE Top Dead Center

[datsunaholic]

... in theory if i were to put the timing mark on the harmonic balancer to 5 degrees below tdc and took dist cap off and rotated the dist and lined the rotor up with #1 on the dist cap wouldnt it be dead on?

 

Short answer, no.

 

Just lining the rotor up with #1 doesn't mean the ignition reluctor is in the proper position to fire.  5, even 10 degrees isn't easy to see.  Plus the centrifugal advance at idle is taken into account in the tuning specification, of which none is applied if the engine isn't running.   That's why you use a timing light and set the timing dynamically with the engine running. 

 

Now, for setting ROUGH timing just to get it started so that you can set it dynamically, your method is about right, assuming 1) you mean BTDC (before, not below) and 2) you are on #1 compression stroke and not #4, since the timing mark on the crank is in the same place for both.

[Mint86720]

Yes i mean before top dead center and it doesnt have a centrifugal its an 86 its all electronic im a master mechanic but my timing light bulb burned out and need to get it as close as possible to drive till i can replace the bulb

[datzenmike]

Crank angle sensor.