I trouble shot a GMC 6 (same distributor) on the phone to a guy in Kansas a few years back that was missing the steel spring and depended on the brass "spring" (actually it was just there to conduct electricity) on a brand new set of points. Wouldn't run faster than 1500 RPM even in neutral. The guy had never messed with a set of points before, so he didn't know what to look for and I couldn't see the missing spring in the pictures he sent. Eventually I sent him my spare tach/dwell meter. Dwell was right on at idle, but by 800 RPM it was starting to move towards zero. Point float just like Jerry said above. By the time the engine got to 1500 RPM the dwell was around 10 degrees.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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