If the guys at Summit were real mechanics, they wouldn't be manning a tech line, they'd be out there bending wrenches. They're mostly there to convert the contents of your back pocket into profit for the company. The duration on that cam sounds OK for street use with a stock converter, but using 1.6:1 rockers turns your lift into .493"/.512", which is a bit extreme. The 1.6's also need about $500.00 worth of head modification by a very good machinist to work right, relocating the rocker studs 1/16" closer to the pushrod side of the head, and adding a set of hardened steel pushrods, guide plates, and screw-in studs. The advantage in lift isn't worth the hassle, plus you're putting the valves dangerously close to the piston tops unless you've milled the pistons for clearance. Take those 1.6:1 rockers off and throw them as far as you can!
The advance curve modification takes a distributor tester, and involves installing a couple of 1/8" roll pins in the slots where the advance weights move to restrict their travel. Whatever gain in initial advance is made must be subtracted from total advance to prevent over-advance at high speed, and detonation/piston damage. When I do that mod, I also modify the reluctor on the distributor shaft to allow speeds of up to 7,000 RPM without spark scatter. A stock HEI distributor starts to crap out at about 5,500 RPM without some special attention.
Did you install real flattop pistons, or do you still have the standard dish-tops the stock engine came with? The original pistons have a .200" dish, plus a chamfer around the outer edge, and the 64CC heads make about 9.5:1 with that setup, just barely streetable with 87 octane gas. Mid-grade gas will perform better, especially with the advanced timing. I still believe your poor performance is more of a gear ratio/torque converter problem than a major error in engine buildup. Email me about the distributor mods if you like.
Jerry
