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This is electrical, but very related to engine design, so.....
Spark advance on engines in the Indian manual(s) is usually spec'd as: 1/2" before top-dead-center" on 74" chief (with 4 7/16" stroke), and 5/8" btdc on 80" with 4 13/16" stroke.
On the drafting board the protractor reads this as approximately 32 or 33 degrees btdc. I have never been educated on spark advance beyond what I've merely picked up on the farm, or in a shop, by observation only. No one has ever elaborated on what determines ideal position for either full power at whatever high rpm, or for idle position.
It seems that 33 degrees btdc is pretty much a maximum advance for 3500 rpm on a standard chief (pinging results from advance beyond that), but it also seems the chevy v-8's that I "farmed" with as a kid did not advance beyond that either, even when, uh, MY BROTHER rev'd it up beyond 5000.
I'd like some discussion on this because if this is common knowledge, it isn't common to me, and I'm not sure that my contemporaries could dazzle me with brilliance either.
Spark advance on engines in the Indian manual(s) is usually spec'd as: 1/2" before top-dead-center" on 74" chief (with 4 7/16" stroke), and 5/8" btdc on 80" with 4 13/16" stroke.
On the drafting board the protractor reads this as approximately 32 or 33 degrees btdc. I have never been educated on spark advance beyond what I've merely picked up on the farm, or in a shop, by observation only. No one has ever elaborated on what determines ideal position for either full power at whatever high rpm, or for idle position.
It seems that 33 degrees btdc is pretty much a maximum advance for 3500 rpm on a standard chief (pinging results from advance beyond that), but it also seems the chevy v-8's that I "farmed" with as a kid did not advance beyond that either, even when, uh, MY BROTHER rev'd it up beyond 5000.
I'd like some discussion on this because if this is common knowledge, it isn't common to me, and I'm not sure that my contemporaries could dazzle me with brilliance either.
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