Different Timing Question, patience pls.

[73c34me]

Read all the threads & have learned alot/ genuine thanks. I understand the importance of vacuum advance on a street strip motor...
BUT, what about a higher compression motor?
Case-in-point. 11.9:1 383sbc edelbrock heads. Victor jr. manifold, big cam.
This car isn't going to loaf along at 2200 rpm. When there is increased cylinder pressure doesn't the need for advance ignition decrease? I have a MSD billet mech. advance only -tach. drive distributor & the old l48 as well. I could rebuild the original to run the vacuum cannistor, but do i need it? the idea of running approx. 50 degrees advance concerns me.. BTW, edelbrock claims these heads like approx. 36 degree total timing. I have been playing around making a system where a vacuum cannister would rotate the entire distributor, rather than use the old cast iron one if need be.

 

[69427]

Read all the threads & have learned alot/ genuine thanks. I understand the importance of vacuum advance on a street strip motor...
BUT, what about a higher compression motor?
Case-in-point. 11.9:1 383sbc edelbrock heads. Victor jr. manifold, big cam.
This car isn't going to loaf along at 2200 rpm. When there is increased cylinder pressure doesn't the need for advance ignition decrease? I have a MSD billet mech. advance only -tach. drive distributor & the old l48 as well. I could rebuild the original to run the vacuum cannistor, but do i need it? the idea of running approx. 50 degrees advance concerns me.. BTW, edelbrock claims these heads like approx. 36 degree total timing. I have been playing around making a system where a vacuum cannister would rotate the entire distributor, rather than use the old cast iron one if need be.

Well, unless all your trips are uphill, you're going to spend a significant amount of time at moderate and high manifold vacuum levels. This means low cylinder pressures, and additional advance is needed at low cylinder pressures to get the peak cylinder combustion pressure to occur at the correct point (15* ATDC).
Every value of cylinder pressure needs a specific timing advance. Compression ratio only tends to skew the timing curve up or down. It doesn't cause it to be unneeded or unnecessary.