Ignition timing vs. AFR?

[DrCharles]

Both are closed chamber and have .039 quench. The aluminum heads will raise the compression a little (from 10.3 to 10.6) and of course will flow plenty more, including low and mid lift.

[rgalajda]

So what is a good mechanical advance curve ?
Example 1:
9.1 compression RV cam
advance comes in slowly
5 degrees initial
32 degrees total
Example 2:
9.5 to 10.5 compression - 230 degree cam at .050" approximately
Mechanical advance comes on faster at first
10-14 degrees initial/slope to 30 degrees at 3000 rpm
34-36 degrees total 4500 to 5000 rpm


Vacuum advance:
Starts 3-5 inches 10-14 inches all in
Cruise 50 degrees approximately

[DrCharles]

I'm not sure what point you're making here. Different engine combos need different advance curves?

Ultimately it comes down to cut-and-try. A cam like mine (272@.050) with mid-10's CR is rarely run on the street, and the drag-only cars don't care about anything but starting, idle (maybe) and WOT. No vacuum advance data there...

But I've found by experiment that mine likes a lot of idle advance, will start hot up to 24, and best WOT power for most Mopar big-blocks is between 34 and 38 degrees! The remaining variables are cruise advance (as you posted, something around 50 deg, and mine is 52), and how fast the mechanical advance should come in.

I need some more street driving to see if I picked the right setting for that last one. There's a cruise-in tonight at the Steak & Shake 8 miles away

[DrCharles]

So far so good... no pinging, improved throttle response AND cooler running by several degrees