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

[mockingbird812]

Nice numbers! Is that a stock set up?

[Johnny Horsepower]

Some pics


John

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[Johnny Horsepower]

It is stock, however they may be inflated because our weight was a guess. I don't even remember how much we plugged in.

It is running stock compression, 100 oct race gas, and pertronix ignition.

Next time i pull, i will grab the weight off of nasty z28

John

[Johnny Horsepower]

I guess we were not that far off and in talking to my engine guru he said it really does not affect those numbers, just acceleration times.?.

[PeteLeathersac]

Possible Coil failure at higher revs or distrib shaft bushings...plugs?.

~ Pete

[Johnny Horsepower]

[ QUOTE ]
Possible Coil failure at higher revs or distrib shaft bushings...plugs?.

~ Pete


[/ QUOTE ]

Thanks Pete, Plugs and coil were on the list. I'll add dist shaft bushings.

John

[MosportGreen66]

cool car

[69LM1]

Gotta love the 70 Z's! Hard to find one with the original engine. Nice car

[Chevy454]

Make sure your coil isn't wired backwards...the car will still run, but won't rev...