īut it will at times detonate WOT on 93 fuel on hot days so if i know i will playing arround a bit i add real lead booster to increase 93 pump fuel to aapprox 98 octane leaded fuel.Īnd keep in mind when the 60's chevy muscle cars were sold new like for examply an l34 396/350hp 10.12 comp bbc chevelle came with sticker stating it required a min of 98 octane/Premium leaded fuel and people expect these old school motors to run just fine on a total different formula pump fuel thats lower octane,non leaded with ethenol added. My bbc with mild perf cam little more agressive FT perf cam then yours & approx 9.8 comp with 20 deg base/38 deg total & 10-12 dev vac adv (proper street perf timing curve) doesnt run on at all on 93 oct pump fuel when shut down idling at 900-950rpm in 90 deg outside temp. Run on/dieseling using todays non leaded lower octane ethenol'd pump fuel in old school sbc/bbc motors is generally caused by motor needing a bit more octane,running a bit too warm overheating carb & fuel with ethenol thats more sensitive to hot temps then higher octane leaded fuel of 40 yrs ago,retarded base timing making you have to set idle screw in so far to get decent idle speed prim throttle plates are out of idle trans circut with motor idling on mains,idle speed set too high,too hot of spark plug heat range to the mix can also help promote run on/dieseling too. So if you set total timing to for example 36 deg and the dist had 25 deg mech adv 36 total minus 25 deg mech adv = 11 deg base timing.Īnd even your mild cam needs a min of 16deg if not 18 deg for best perf so in that case base timing would be 5-7 deg retarded which is a lot and kills perf in all rpm esp comming off idle in rpm below where mech adv is fully in. Why,that because doing that often leaves base timing very retarded ,just how much depends on what mech adv setup is in dist at the time.įor example,if your running a stock gm point type dist even one with a point conversion/elimination kit in it often came with 25+ deg mech adv in them. 36-38 deg total is very common for pump gas motors running on 93 oct pump fuel with moderate compression.īut setting timoing for total only on street is wrong thing to do!
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