Adjust dizzy using light/without light A12/A15

[Datsun fan]

Hey guys , this site is a great source of pre-hands-on info!!!

I'm just confused about how to adjust distributer advance after I installed stock electronic one , should I use timing light or just counting on my limited experience ?? what are the steps ?? the whole engine is stock A12/A15 and set as stock except plugs are set to 2.1 mm for stronger performance and better mpg

[ggzilla]

Use a timing light. 7 degree BTDC at 600 RPM.

 

You can do it without a light.

1. Turn engine by hand, line up timing mark at 7 BTDC

2. Pull cap, and turn distributor until the teeth line up

3. Drive it low rpm 2-3k, medium and full throttle.

* If it pings turn back two degrees (anti-clockwise)

* If it doesnt ping turn forward two degrees (clockwise)

Repeat step 3 until it pings and until you set it back.

 

Base timing

 

Fine tuning

Edited June 13, 2009 by ggzilla

[Datsun fan]

Well , that looks pretty easy but, The cranck pully I've doesn't has that notch so how to set 7 deg BTDC ??

I've heard from somewhere that turning dizzy towards A or R will optimize engine for MPG or performance , is it right ?? I want to know more .and oh!!!

thanks for your fast reply .

[datzenmike]

When the gas and air in the combustion chamber is ignited it takes a set amount of time to burn it no mater how fast the engine is turning. The trick is to start the burn so that it is expanding with maximum force just after the piston passes top dead center (TDC) and is on it's way down the cylinder. The optimum spot is about 17 degrees after TDC. At idle the optimum advance is about 7 degrees before TDC. As the engine speed increases there is less time before the piston gets to this ideal 17 degrees yet the fuel and air still take the same time to burn. The piston will pass this spot and travel further down the cylinder and the expanding gasses have to chase it to push on it. The problem can be solved by starting the burn sooner so that the maximum cylinder pressure still occurs at about 17 degrees after TDC. This can be done by a mechanical device in the distributor consisting of two spinning weights that are flung outward by centrifugal force in relation to engine RPMs. This movement is used to advance or retard the ignition timing to keep within the ideal 17 degrees after TDC. How simple is that???

[Datsun fan]

I bow to your superior knowledge about core petrol engine fundamentals . But my question is still needs answer , how the hell can I catch exact TDC position with no-notch pully ????? I know this is a dumb question but you guys know , It's not a shame to be dumb but it is shame to STAY dumb !!!!!!!!

[ggzilla]

Datsun A-series engine all have a notch on the pully. Earrly evgine have several nothces. Look at the pully carefulyy nothc is on inside not on outisde.

[Datsun fan]

I made double check of the pulley ...... damn !!!!! there was NOT ANY notch I swear in that pully . Anyway used a pencil and my eyes for base timing and guess what !!!! the engine didn't ping or the pinging was rare !!!! setting correct valves clearance 0.014" helped getting good ping then retarded 2 degrees ( 2 grooves on dizzy plate anti-clockwise , is that correct ??) .

the engine now is pretty nice tuned !!!!!!!!!! thanks man I appreciate yuor response .

[ggzilla]

Sounds right. Happy motoring.