360 Tune Up
Edited my previous post to clarify the timing plots are at the bottom of that post.
Looking at the DC/MP instructions for their distributor, at least in the mid to upper rpms, my interpretation is the magnum engines create faster developing flame fronts. This is suggested because instead of targeting 35* at 2800 rpm, they suggest 32* at 2800 rpm.
How To Limit and Adjust Chrysler Vacuum Advance Cans
aside:
They aren't providing an initial because it they are offering a 'one size fits all' distributor. They can't predict what sort of cam etc has been put in, but they know the users are most concerned about hih and mid rpm performance. Also getting the timing close in the higher rpm ranges is more critical than the low. Worst case with low rpm is poorer milage, less torque, maybe some pinging or "gurgling sound' at par throttle. Worst case at high rpm, high load, is melted piston or similar.
Returning to the example using the MP distributor and setting the timing as they suggest, the timing curve would like this.
Most of the Chrysler engines we are dealing with like a fairly quick rise in timing going from idle to around 1700 rpm.
Then slow the increase in timing is reduced greatly because the combustion itself is getting faster. That's why it doesn't need continued rapid increases in lead time. It only needs more lead time when we reduce the density of fuel and air which is dealt with by the vacuum advance.
Edited my previous post to clarify the timing plots are at the bottom of that post.
Looking at the DC/MP instructions for their distributor, at least in the mid to upper rpms, my interpretation is the magnum engines create faster developing flame fronts. This is suggested because instead of targeting 35* at 2800 rpm, they suggest 32* at 2800 rpm.
How To Limit and Adjust Chrysler Vacuum Advance Cans
aside:
They aren't providing an initial because it they are offering a 'one size fits all' distributor. They can't predict what sort of cam etc has been put in, but they know the users are most concerned about hih and mid rpm performance. Also getting the timing close in the higher rpm ranges is more critical than the low. Worst case with low rpm is poorer milage, less torque, maybe some pinging or "gurgling sound' at par throttle. Worst case at high rpm, high load, is melted piston or similar.
Returning to the example using the MP distributor and setting the timing as they suggest, the timing curve would like this.
Most of the Chrysler engines we are dealing with like a fairly quick rise in timing going from idle to around 1700 rpm.
Then slow the increase in timing is reduced greatly because the combustion itself is getting faster. That's why it doesn't need continued rapid increases in lead time. It only needs more lead time when we reduce the density of fuel and air which is dealt with by the vacuum advance.
