I've been bored lately so I have been doing some fine tuning on my 250. I've got the Ignitor 1 Pertronix kit installed right now. I run the motor on 87 octane and it's a daily driver. I had the plugs set at .035" (points spec) so I opened them up a little last night to .042". The engine seems to run a little smoother, the plugs are nice and tan(all 6). I was wondering what some of you other guys are gapping your plugs at with HEI or Pertronix kits. I looked in my Haynes manual for '67-87 Chevy trucks and found something interesting.
If I remember right 1975 was the first year for HEI, right? For 1974 Haynes' lists 250,292,350,454 at .035" gap. 250 uses plug AC-R46T, the rest use AC-R44T. In '75 they list 250,292,350,400,454 at .060". 250 uses AC-R46TX, the rest use AC-R44TX. In '76 they list the 250 and 292 at .035" and the 350,400,454 at .045". The 250 uses AC-R46TS, 292 uses AC-R44T, 350-454 uses AC-R45TS.
I know this is alot of info, but what gives? If HEI started in '75 and they increased the gap why in '76 would they go back to .035"? I just find this odd. Doesn't a hotter spark allow you to increase plug gap, which will provide better combustion of the air/fuel mixture and decreased emissions? I'm just trying to get an idea of what will be about right for my truck. Thanks guys. John.
