my 70Z dyno tune

[Johnny Horsepower]

for those of you who remember, i was having an issue with exhaust popping when backing off on my 70 Z28. We threw it on the dyno, and clamped the smog hoses. Cured it so we installled freeze plugs. We then decided to do a pull. Much to my chagrin, we discovered spark degredation at about 4850 rpm. Car would quit accelerating.
Now we have to hunt that down. We are going to start with the date coded wires. Any suggestions?

In the meantime the aborted pull to 4850....
300 rwhp 375 lbs

John