As far as timing, my 670 semi-open chamber street heads run best at 38°. My first generation Edelbrock round ports that flow 349cfm liked 41° on the dyno and at the track. Most of the Kaufman heads were between 31° and 32° on the dyno, and the later generation Edelbrock heads ended up at no more than 34°.
My MSD Digital 6-Plus had a strange quirk where it would not always do the 20° electronic retard. Did enough checking where the failure to retard had to be inside the box itself. I gave up fighting it and went to a set of springs just strong enough to bring the weights back on shutoff. When the box retarded the timing the locked distributor worked great, but when it didn't work the engine was really unhappy on start up.
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Mick Batson
1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 2+2 survivor AC auto -- 1965 Catalina Safari Wagon in progress.
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