Ignition Timing

[Classics Fan]

This is my first foray into distributor recurving. I have a GM HEI on original 350 with Edelbrock Performer intake and RV cam, rebuilt .030 with 9.0:1 pistons and original heads. Ported vacuum advance that comes in with bare tip-in of the throttle. The engine ran well but was sluggish. I replaced the OEM center plate, weights and springs with Mr. Gasket parts. The smallest (black) springs are way too light, coming in at 900 RPM. The next size up (silver) work much better, coming in at 1650 RPM BUT I can only get 10 degrees mechanical advance at 2250 RPM. Initial advance is16 degrees so total all-in is only 26 degrees. The curve diagram from the Mr. Gasket kit seems to show the weight/spring combo only allowing 12 degrees or so. If I advance initial much more than 16, it is hard to turn over. Any thoughts or ideas how to get total timing up to between 34 and 36 degrees? By the way, it runs better than ever as it sits now.
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