At 10:59 am 8/11/97 -0400, you wrote:
>I've got the same problem and I've got a couple of basic questions.
>Does the old tach not self adjust for dwell?
>Due all new Tachs adjust for dwell?
>What is dwell angle? I know how to measure it, but I'm not sure what it
>is.
>Is calibrating the old tach against a "modern" new one a good idea?
>Will having both tachs hooked up effect the test negatively.
Parlee,
Dwell relates to the number of degrees that the ignition points
are closed ( and therefore charging up the coil for the next spark.)
On a 4 cycle motor the the piston has a power stroke every other revolution.
Therefore with an 8 cylinder motor there are 4 power strokes per revolution
or one every 90 degrees (i.e. 360/4). The dwell on an 8 cylinder 4 cycle motor
is therefore the number of degrees that the points are closed out of 90
degrees. Typical dwell is 29 to 32 degrees on an 8 cylinder motor.
Less dwell advances the timing and if you turn a high enough RPM
there is inadequate time to charge the coil. Your spark gets weak at
high RPM if the dwell is too small. Dwell that is too large will retard
your iginition and possability lower your power.
Recommend that you set your dwell to specifications and then reset
your timing to specifications ( or your desired advance).
Jim Barrett Tiger II 351C and others
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