Manifold Vacuum Advance what am I not getting?

Bewy said
Well that is your 'typical' engine that we see folks asking about the use of MVA:
- 12:1 CR.
- 255 @ 050 cam
- tunnel ram with 800 cfm carbs.
- revs to 7000ish

Yeah everybody has one, there are three in my street alone.....

That engine would STILL idle better with more than 20* initial......whether you are honest enough to admit it or not. One way to add idle timing is MVA. It is not the only way. But MVA is simple, inexpensive & reliable. And sure, you could run with 5* initial timing. But it would not be the most efficient, & the engine would run hotter. Why wouldn't you [ or anybody else ] want the engine to run as efficiently as it can???? One reason you are running 12:1 & 0.040" quench & not 10:1 & 0.125" quench is because you want maximum efficiency.

How do you know it will want more timing at idle? Are you that ******* arrogant that you think I won’t test it?

The last 4 or 5 Chryslers on my dyno, all 408’s and none over 11:1 didn’t want MVA at idle. I think the most one of those wanted was 24 and the cam was too big for the compression.

And guess what Geoff, I tested ALL of them with locked out timing and NONE of them idled better with 34-35 at idle. And ALL of them made more power with a curve.

So there you have it. And none of those engines are exceptional or odd. And most of them had more cam than the compression wanted but to get the rpm out of them that’s what you have to do.

And still NONE of them wanted all that idle timing.

Try again.