20 MPG from triples? My set-up works fine 42DCOE, mechanical advance distributor, MSD 6AL, Petronix, but 20 MPG ... not even close. I think I'm getting like 8 MPG at the track.
Picture shows OEM distributor and vacuum advance. That set-up, did not work well. Classic bog at 1500 to 1800 RPM. In hindsight, I think timing advance had a great deal to do with it and not just the mechanical advance. We also took advice from Jeff Winters on the air corrector, idle jets, and other parameters. Even changing the plugs helped. So I can't say all my results were from the mechanical advance alone.