Much as we dig all the chances we get here at cHP to create some of the hottest motors going, have you noticed what happens after we build 'em? That's right, we bolt on new parts and dyno them again, always in search of more power. Heads, cam swaps, intakes, nitrous, superchargers, and anything else we can think of. We're betting you can relate, 'cause we ask the same question you do: What can I do to make more power without tearing the whole thing apart again? enter the bolt-on. You spend a few hours removing one part and replacing it with another, and you make more power. Or at least you hope you do. In that spirit, we once again dive headfirst into the bolt-on world, selecting performance parts and putting them to the test.
As we do in these investigations, our line of attack was clear cut. We had to either obtain-or produce-before and after dyno sheets so that we had clear evi dence on any particular piece's effectiveness. claims without evidence were not even considered for this endeavor. Thanks to the engine dyno at Westech Performance, Granatelli motorsports' chassis dyno, and our punishing multiday dyno thrash at the SOuRce INTeRLINK media Tech center, we got the numbers. Why punishing, you ask?
When it came to our choice of mules, we've focused primarily on traditional small-block performance pieces but tried to add a little variety to the mix by including some big-block and LS1 hop-up goodies as well. That being said, we have to point out that we got the chance to try out several bolt-ons on a nearly bone-stock '70 chevelle SS. This particular mule, which kept its stock heads and cam throughout the testing, gave us the chance to see what a variety of performance parts can do on an original motor-and reminded us how much work it is to keep such a powerplant's original equipment and accessories working while making modifications, all the while leaving it so that it can be returned to original if the owner so desires. It's tough, but the cool thing is, it can be done.
Many of you won't be starting with such an untouched powerplant, but we bet more than a few of you out there are running stockers and considering that first modification (or two). The appeal of the bolt-on part is hard to resist, and now we've given you some food for thought. We've endeavored, however, to incorporate useful information for just about everyone, including those of you who are already far beyond the original equipment stage. To that end, we've included average power numbers to go along with the attention-grabbing peak power numbers, with an eye toward evaluating how a given bolt-on affects performance throughout the powerband.
In the main, we'll let the numbers speak for themselves, keeping commentary to the bare essentials. We've done the testing and published the results; we hope the information proves helpful as you go forth to bolt some power on to your project.
Quick NotesWhat We DidPulled together 13 bolt-on performance parts and got real-world before and after dyno numbers
Bottom LineThere's a multitude of ways to endow your ride with a few-or a lot-more ponies.
Price$82-$3,500
Dyno Thrashin'Big-Block Cylinder HeadsThe Bolt-OnEdelbrock Performer RPm 454-R aluminum cylinder heads, which have 315cc long/300cc short rectangular intake ports, 118cc open combustion chambers, and 2.19/1.88-inch valves. $1,780/pair
The MuleA 502 H.O. chevy short-block with factory iron rectangular-port heads, 8.75:1 compression, topped with an edelbrock Performer RPm 2-R intake and 800-cfm AVS carburetor. Power measured at the flywheel.
Our TakeAccording to edelbrock, the runner con-figuration optimizes intake and exhaust flow, especially on the short side, while the combustion chambers are designed to maximize chamber efficiency. In this case, it all adds up to nice power gains on the dyno.
BeforeMax torque: 518 lb-ft @ 4,000 rpmMax power: 452 hp @ 5,000 rpmAverage torque: 485 lb-ftAverage power: 367 hp