Ha not a question about ported vs manifold vacuum LOL. not going there
SBC 350 assume stock HEI with vacuum and mechanical advance
Simple ? really: Is vacuum advance added to or incorporated within the mechanical ?
In looking at how the advance works I'm not 100%.
E.G. say I'm at 12 deg no vacuum, base timing ( I am)
and I hook the vacuum advance hose to manifold vacuum, at idle 750, I may have another 15 deg so 12 + 15 = 27
So as rpms increase, high load , WOT, low vacuum the mechanical advance will begin at what RPM? and advance to what degrees?
I'm thinking its not as simple as 12 + 15 + say 15 more from mechanical.
At steady cruizin say 2300 RPM light load, I would think there would be upwards of 25 deg, and no or little mechanical advance.
I cant imagine any scenario where I would have full vacuum and full mechanical.
I'm thinking the vacuum advance exists "inside" the range of the mechanical... if the vacuum is pulling ten degrees the mechanical would have to get up to that ten degrees and past it to effect timing. But as RPMs increase vacuum drops, so the "Passover point" would change?
Is there a scenario where the would fight each other?
Thanks
SBC 350 assume stock HEI with vacuum and mechanical advance
Simple ? really: Is vacuum advance added to or incorporated within the mechanical ?
In looking at how the advance works I'm not 100%.
E.G. say I'm at 12 deg no vacuum, base timing ( I am)
and I hook the vacuum advance hose to manifold vacuum, at idle 750, I may have another 15 deg so 12 + 15 = 27
So as rpms increase, high load , WOT, low vacuum the mechanical advance will begin at what RPM? and advance to what degrees?
I'm thinking its not as simple as 12 + 15 + say 15 more from mechanical.
At steady cruizin say 2300 RPM light load, I would think there would be upwards of 25 deg, and no or little mechanical advance.
I cant imagine any scenario where I would have full vacuum and full mechanical.
I'm thinking the vacuum advance exists "inside" the range of the mechanical... if the vacuum is pulling ten degrees the mechanical would have to get up to that ten degrees and past it to effect timing. But as RPMs increase vacuum drops, so the "Passover point" would change?
Is there a scenario where the would fight each other?
Thanks