Can there be any doubt that bolt-ons are the lifeblood of our hobby? Granted, parts that take a bit more time to install-things such as pistons, camshafts, and stroker cranks-can lead to big power gains. But you show us a guy who meticulously builds the perfect, tire-shredding powerplant for his classic Chevy, and we'll show you a guy who still can't resist the urge to bolt on a few more horsepower. The attraction is easy to understand: You buy a part for your application, spend a few hours in the garage bolting said part on, and you make more power. That's the way it's supposed to work, anyway.
And that's the shape of this month's dyno thrash. In a nutshell, we picked out a bunch of bolt-ons, then produced dyno numbers to document actual power gains.
Our methodology for this project was pretty straightforward. For any given part, we had to have before and after dyno sheets in hand to report on that piece's effectiveness. It was as simple as that. No approximations, no unsubstantiated claims. As a gearhead-minded Joe Friday might have said, "Just the facts, man." Much of the data we've collected here came from the test archives of respected dyno facilities, places such as Westech Performance and Vrbancic Bros. Racing. The rest of the info, lest you think we didn't get our hands dirty during this investigation, is the result of a punishing, two-day dyno thrash at Granatelli Motorsports. J.R. Granatelli and his staff, specifically Morgan, Ralph, Martin, and Jeremiah, ran cars on and off the dyno, wrenched when needed, and put in some substantial overtime to make this report possible. When these guys take on a project, they take it on all the way.
In choosing our mules, we tried to pick combos that span the performance spectrum, focusing mainly on traditional small-block performance. We won't claim to be all things to all people, but we think everybody can find some useful information here. Speaking of useful info, we've listed peak power numbers, of course, but note that we've also included average numbers to help you evaluate how a given bolt-on affected performance throughout the powerband. In one case, we were even able to record an increase in gas mileage to go along with our power increase, which was certainly a bonus.
As for the numbers, for the most part, we're gonna let them speak for themselves. Some of the results aren't all that surprising; others, however, were unexpected. All of them are dyno proven, and our hope is that the info here will make your next bolt-on purchase that much easier.