I assembled the engine myself with a new Summit SFI damper barely 3 years ago and the timing marks were spot-on. I am using a multi-spark box but it's made by Mallory not MSD, I am aware of issues with those and the dial-back timing lights and mine is a regular one; I don't need a dial-back light as the damper has timing marks all the way up to 60* BTDC. I also know the parts you mentioned are all good I am using a mini-starter which cranks super fast; I do need a new battery but this was happening even when I had a full charge. It would kick back before the engine even had a chance to turn over once, literally almost instantly after I would turn the key to crank the engine.
I even Sea-Foam'd the engine (twice) to remove carbon which I thought was causing hot spots and preignition but that made no difference. Something I do notice now when I crank the engine hot with no spark it "sputters" a bit like the fuel-air mixture is igniting itself solely from compression and heat... My combo is a little "unusual" I have a 360 bored .060" over with KB flat-tops and factory iron Magnum heads (with factory 1.6:1 rockers), true static compression was verified during assembly at 10.42:1 and like I said the cam is very small for the cubes/compression this engine makes MONSTER torque on the bottom end and runs perfect aside from the starter kick-back I had before I did this ignition mod.
