Ignition timing question

[Bruce R.]

Working the bugs out of my Merc, with the timing spot on at 6 degrees it dont run worth a damn. Does the Crane cam I used have anything to do with that ? If I advance it it runs better but how far can I go ?

[My427stang]

Most any FE will like 12-14 initial, even with the smallest of cams.  The challenge is with the rest of the curve, you don't want to over advance.

Is it a stock distributor?  A good rule of thumb is to get 22 or so mechanical advance, set initial to 14 and vacuum to ported.  Works with most and you can tweak from there.  Stock settings like 6 BTDC are for stock engines with little cam and really weren't good for the engines back then either

[Bruce R.]

Yeah, stock distributor with a Pertronix unit, cam is 216 dur. 530 lift

[Falcon67]

When I used a curve, my idea was to run as much initial as the motor could stand - as much as 18 in some cases - then limit total to a reasonable figure.  Usually on my SBFs, 351Cs somewhere 34~38.  It takes work but it's worth it.  Or take the 21st century way out - lock the timing at full advance and use a programmable ignition to insert a start retard of 10~20 degrees.