Ignition timing with/without vac advance....sticking?

Trace 300 Hurst

Professional Tinkerer
FCBO Gold Member
May 27, 2018
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Ponte Vedra Beach, FL
forgive my nomenclature i can find no reference online to using " - " and " + " symbols to reference timing. only BTDC and ATDC. again my apologies.

logic would assume that if
TDC = 0
a number smaller than that, or previous to that, would be " -" number
and, conversly, a number greater than 0, or beyond zero, would be marked as " +" number.

so, in the summit racing instructions that come with the 850005 distributor kit orange box for 440, it says set timing to 5 degrees BTDC, is what i meant when i said -5*.

im not sure how yall interpreted it to be a positive (i.e. ATDC), thus the clarification.

your pal -

- saylor
Thanks for the clarification, and yes I'd say we all agree that BTDC and ATDC are accepted terms of timing, far more so than Neg or Pos. As you pointed out, you can interpret - or + to mean either side of TDC depending on your point of view. Let's stick to B and A!