I have Pertronix kits and coils on my '68 318, and my '70 383, both Sweptlines (lower compression). I run my gaps 0.040 instead of factory 0.035. I've heard that gaps that approach 0.050 cause a rough idle, but run fine as higher rpms. My idle is a little rough, it could be a contributing factor. Dunno. I get 10/16 mpg with the big block/727/3.54 hauling a trailer, and highway unloaded at 55 respectively. That's about 20% better than before the pertronix. The 318/NP435/3.75 gets 16-22, depending on how hard I drive it.
