For instance:
Gm says to set idle timing at 8 degrees but Jimw found that 12 degrees worked best for him.
That is not what GM says 8 degrees for what works best for power or mileage.
GM sets it at a certain timing for less emissions.
My moms 73 Nova 250 L6,,, GM set timing low for emissions.
I used to advance the timing to get better performance & better mileage.
The best mileage my Moms car ever got on road trips was 16 MPG,after I adjusted/advanced the timing it got 2-3 more MPG.
When I left the timing advanced & forgeting it was advanced,, I smog tested it,,,well, it failed emissions/smog test.
Put the timing where GM stated it to set it at,,it passed.
Glad we don't need to smog all the old cars still.
MBHD
