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. The 750 was square all around with 73 jets, but we needed to lean it out a bundle. We dropped the primary jets down to 71s, and the secondaries to 68s. That's a two-step and a five-step downgrade front and back. The result was a better air/fuel ratio, but the same power. The 750 was square all around with 73 jets, but we needed to lean it out a bundle. We drop Last but not least, we laid down the 670 cfm Street Avenger carb atop the 396. Even though the air/fuel gauge showed a slightly lean condition, it didn't warrant us to lift our foot off the throttle, and the Chevelle cranked out 195 horsepower and 281 lb-ft of torque. We tried playing with the mixture screws to lower the air/fuel, but to no avail. Alas, we were going to have to change jets. Last but not least, we laid down the 670 cfm Street Avenger carb atop the 396. Even though Not wanting to mess with the great tip-in the 670 gave us, we only adjusted the primary side of the fuel mixer. The primary jets were 65s, while the secondaries were 68s, showing that the primary circuit was a bit leaner. With that in mind, we went up four jet sizes to 69s, and then slammed the loud pedal down one last time. The result was 199 horsepower and 287 lb-ft of torque. Not wanting to mess with the great tip-in the 670 gave us, we only adjusted the primary si SOURCES Tune Time Performance 7-32/-349-7800 www.tunetimeperformance.com Holley Performance Products, Inc. 1801 Russellville Road P.O. Box 10360 Bowling Green KY 42102-7360 270-782-2900 N/A www.holley.com/ « | 1 | 2 | View Full Article By Frank H. Cicerale Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!