I has it a guess its more to do with tune,in there some where like loose springs on your dist advance, wrong fuel level in carb, needle & seat,butterfly etc loose, have you checked the valve clearance/ tappets etc with unleaded you may have valve recession[sinking into head] due to wear. Check compression..But I would think this to be more of a consistant miss rather then high/ low idle..
Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic!
Tuned & maintained by "Peppertree Perfmormance". Dart block, Scat 4340 steel crank, Custom C.P pistons.Oliver rods.. Mal Wood twin plate clutch.. Twin SC61/2's,482 rwkw/ 645 rwhp..
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