84 Nissan 720 timing question/issue

[Kaisin2k]

Hello,

I am new to the forum here but have found a lot of useful help and information regarding the restoration and fixing of my 84 Nissan 720.

The current issue or question that I am having is due to the ignition timing. Are all 4 cylinders supposed to fire at the same degree before TDC or is it intentionally staggered?

I have cylinders 1 and 4 clocked with a timing light at 5-6 degrees before TDC without any vacuum advance but for some reason I can't even get the timing notch to light up on the 45 degree arc before TDC with cylinders 2 and 3. I further suspect that they are firing late because when the engine is under load I get some sounds of detonation as the truck accelerates.

All spark plug wires have been checked and are within tolerable resistance and the air gap for the reluctor is within spec as well. The cap and rotor have been replaced also so I'm at a loss as to what could cause this late firing in only 2 of the cylinders.

Any help or input would be greatly appreciated.

The engine is a z24 carburated.

Thanks for your time,

Mike