Awful MPG, but drives good?

[essenz]

Rather than at idle, check the timing at 500rpm increments or so if you can from 2000 to 5000. Want 36deg total timing at about 3800+ rpm. Then let the idle timing land where it may. If this puts idle timing at much above 15, without vac advance, then you may need to work on the dizzy or retard timing to prevent low speed ping.

I've been curious about the dizzy's advance, dumb math question.... so in neutral at 800rpm Im at 10 BTDC, I bump up in increments of 500 to map the timing curve, and you at 3800rpm I should be around 36 deg total timing - is that 36BTDC (or 10BTDC - 36 = 26ATDC), sorry for the dumb question. My crank pulley only has 0 to 20 BTDC marks, but I could make a 30 and 40 BTDC notch and do this test.

[Nut124]

Timing at and above 3800rpm should be about 36deg BTDC with any vac advance disconnected.

Typical dizzy has about 26deg mechanical advance plus the 10deg static advance at idle = 36. However, many old Fiat dizzys do not yield the 26 mechanical or yield it too early. So you could end up with 21 mech and set idle at 15 for the same.

They make timing lights with dial up advance. This way, you'd always be watching the TDC zero deg mark and adjusting the light until the zero marks align.