The dwell on my 65 and 69 should be 30 degrees according to the service manuals. Is this at an idle? I ask that because I notice when I rev the engine to say 1600 rpm, the dwell drops to 20. Is this normal or is my guage not reading right. It won't read rpm any more, so I'm wondering if the gauge is reading dwell correctly.

Marley,
The dwell should be the same (or very close) at all rpms.

I think it's time to retire your meter.

thanks bill and badrat; I thought my meter was out but I wanted confirmation. So another tool to buy. Wife will be impressed.

Marley,
If the distributor is the GM window type, all you need to do is start the engine, then turn the adjusting screw clockwise until the engine starts to misfire. Then turn it back 1/2 turn. It will be within a degree or so of 30. This procedure is straight from the GM factory manual.

Could also be a bad distributor. How loose is the main shaft?

Thanks all. It turned out to be my dwell meter went bad. I bought a new one and when I set it to 30 degrees, runs nice, and almost no change at higher rpm. I probably toasted my old one due to incorrect hookup. I never had directions with the old one someone gave me. The correct hookup, based on the new one I bought is, red wire to "-" post on coil (the wire that goes to distributor) and the black wire of the gauge goes to engine ground somewhere convenient. The half turn back from a miss is probably bang on in my experience. Thanks for that tip.