The Ford Barn - View Single Post

drolston · 11-26-2019, 11:20 AM

Crab with Pertronix on 87 Octane. Factory ported 284 inches with 425 Offy heads equals compression ratio about 8.5:1 Adjustment on distributor set to full advance; vacuum brake set for a light touch. Was getting a little spark knock, most noticeable under moderate acceleration in second gear. Backed off 2 degrees on the advance and could still hear a little. Went in one turn on the brake on the distributor and that cleared it up.

11-26-2019, 11:20 AM	#9
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,627	Re: Flathead "spark knock" ??????? Crab with Pertronix on 87 Octane. Factory ported 284 inches with 425 Offy heads equals compression ratio about 8.5:1 Adjustment on distributor set to full advance; vacuum brake set for a light touch. Was getting a little spark knock, most noticeable under moderate acceleration in second gear. Backed off 2 degrees on the advance and could still hear a little. Went in one turn on the brake on the distributor and that cleared it up.