1931 Engine Timing - Page 2

Some information about the dwell and timing on a Chev six cylinder engine.

Ignition Points Gap
For our purposes, I'm using the VCCA-member recommendation of ignition gap of .018 along with dwell of 36 degrees and a spark plug gap of .040.

Before setting the point gap, make sure that both ignition point surfaces are completely flat.  File them if necessary.  The number one spark (plug wire) position in the distributor is at approximately 6 o'clock on the distributor housing. 

There is a screw is in the body at approximately that location. 

Since the shaft rotation direction is clockwise, the next plug wire is in a clockwise direction.




CONCLUSION:  Made sure that the number one plug wire is a the correct location on the distributor and that the remaining wires follow in this order - 1-5-3-6-2-4.

What is dwell?   This is the time when the points are closed and the coil is being recharged.





Since there are six cylinders in our engine, the distributor shaft has six sides.






The distributor goes through six complete firing cycles during each revolution.  The points are either closed or open during these twelve "windows".







The most significant aspect of the dwell window is to recognize when the actual spark occurs.  Since the rotation is clockwise, the front of the close window is when the points first come together. Then they remain closed until the window passes.  The spark occurs just as the points "open". 





Each of the six "closed" windows has the spark location at the end of the window.





The dwell setting that we were trying to achieve was 36 degrees.

We managed to set the points as close as we could to .018 and our dwell reading was 34 degrees.  So the question was, "Is this close enough?"




Looking at this diagram, you can see that our lower dwell reading of 34, only changed the spark timing by 1 degree.  Trying to change the ignition points gap setting to get 2 more degrees was probably not feasible.


Diagrams by Bill Barker

 Index Dwell Meters Points Gap - Dwell Timing Distributor BTDC