Last but not least was the 670 cfm vacuum secondary Street Avenger carb supplied by Holley. We slapped this puppy on, rigged the electric choke to stay open, and fired the fat-block Chevelle up. After playing with the mixture screws, we stood on the loud pedal, where the 670-equipped 396 recorded 195 hp and 281 lb-ft of torque. With the air/fuel reading for this car also being lean, we made a primary side jet change. The jet change made a difference in the air/fuel reading on our last dyno pull of the day, as it lowered it from the 14.0:1 range to 12.7:1. The Chevelle missed the 200 horsepower mark, though, recording 199 rear wheel horsepower and 287 lb-ft of torque
Overall, we spent a day at the dyno with a big-block Chevelle, and drove out with seven horsepower and 17 lb-ft of torque more than what we went there with. While we could have spent the money on either of the Holley carbs and made respectable power, but adjusting the mixture screws on the Quadrajet and adding timing to the engine, we picked up 10 lbs-ft of torque and six horsepower just by tuning what we had on the car when we got to the dyno. For the price of what it would cost to have your muscle car chassis-dynoed and tuned, we would say it's money well spent.