I could not think of a very descriptive title. The issue became apparent last month during a racing weekend and we replicated it on the dyno today. I have a 1992 305 TPI set up for the Camaro-Mustang Challenge series. In other words, stock internals, ignition and exhaust.

One the first pull (around 180-190 engine temp) the dyno graph looks great. There is nothing a miss. But on subsequent pull (temp 190-200) it is cutting in and out. The numbers are not bad, but the dips in the graph are noticeable. By the third pull, there is a serious dip at 3600 RPM and the engine never recovers.

The computer is not adding or removing timing, verified that. We replace the MSD coil with a known good one to no avail.

The only other oddity is the initial timing is changing by itself. At the track it dropped from 6 degrees BTC to 4.9 BTC. On the dyno it actually went up from 8 to 10 BTC.

The car has brand new plugs, wires, distributor, rotor, etc. The car idles fine and is not showing anything abnormal with the timing light.

Our thought is the distributor. Any other ideas...

attached is the dyno sheet from today.