1931 Engine Tune Up - Page 1

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

Today we got four dwell meters together with the help of my buddy Dick Olson.  We have been working on the timing of his 1931 Sport Coupe and my 1931 Five Passenger Coupe.

We had found that the point gap setting didn't seem to line up with the dwell readings that we expected.  So we became suspicious of the calibration of our dwell meter.  We thought that we might compare this to as many meters as possible on the same engine.

The first thing that we noticed was that THREE of the four meters that we had were made by the same company (Dixson)  in Grand Junction , Colorado.  This was an interesting coincidence since the reason that I was timing my car was to get it ready to travel from Seattle, Washington to Grand Junction, Colorado for the National VCCA Meet later this month!!!

The following section lists our findings along with some additional information that you might find useful when timing your car's engine.

<Click on any photo to enlarge it>

Tune up specifications for an early 30's Chevrolet
The recommended settings that is listed in most 1931 Shop Manuals is
    Spark Plug gap .024
    Ignition Points gap .018
    Timing 12 degrees BTDC
    Dwell - not listed in 1931

The experience of most VCCA members is that these engines run much better at the following settings:
    Spark Plug gap .040
    Ignition Points gap .018
    Timing 18 degrees BTDC
    Dwell 36 degrees
See here for an earlier posting about this timing combination. 

Also, in later years, most Motor's Manuals list the following as the tune-up specifications for early 30's engines:
    Spark Plug gap .040
    Ignition Points gap .022
    Dwell 31-37 degrees BTDC, with the most common being 36 degrees.

The order of your tune-up should be:
    1) Spark plug gap
    2) Ignition gap with confirmation of dwell angle
    3) Timing

Recommended:  AC C86 are not available.  Most people try to use AC C87 which are available.  Another thing of interest is that when the plug gap is increased to .045" a longer duration of spark occurs and the car runs even a little better than when the spark is at .040".   Either gap is good but .045" appears to be even a little better.  If you're nervous to make it this large, then just go to .040".

CONCLUSION:  The VCCA-member tune-up settings have been found to be the best combination.  This gives us power at cruising speed, easier starting, smoother idle, better throttle response, and probably more miles per gallon of gas. 

Note:  The VCCA does not officially sanction any of these recommendations, and they are considered to be "member suggestions" only.

Dwell Meter Comparisons at Point Gap of .018
    Dixson 1501             --> 37 degrees
   Dixson 1376             --> 28 degrees
   Dixson Pro Tester 10 --> 32 degrees
   Sears 244.21032        --> 34 degrees
CONCLUSION:  Dwell meters have a lot of inaccuracy in them.  The Sears meter was the most trustworthy since it allowed the user to "zero" the needle twice, once at rest, and again with a charge on it.  We were shooting for 36 degrees and decided to leave the ignition gap alone since it was reading 34 degrees with the Sears meter.  This was considered well within an acceptable margin of error.
Photos by Bill Barker

 Index Dwell Meters Points Gap - Dwell Timing Distributor BTDC