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 evidence 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.
What we did
Pulled together 13 bolt-on performance parts and got real-world before and after dyno numbers
There's a multitude of ways to endow your ride with a few--or a lot--more ponies.
Things get interesting when you start stacking one bolt-on on top of another--with the right mix, you can get a nice power payoff.
Vortech Superchargers standard small-block carbureted kit with a V2 S-trim compressor running 5.5 pounds boost, along with a Mighty Demon 750-cfm blower carb. $3,500
A '69 Nova with a bone-stock 350 lower end, '70s-era open-chamber heads with 1.94/1.50-inch valves, an Edelbrock Performer intake, a Holley 650-cfm vacuum secondary carb, and a Turbo 350 transmission. Power measured at the rear wheels.
Even on this very tame engine, the Vortech blow-through setup increased power by almost 50 percent at the wheels; we calculate the gain at the flywheel to be right about 100 hp, which shows that even a small blower setup can produce big gains.
Big-Block Cylinder Heads
Edelbrock 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
A 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.
According to Edelbrock, the runner configuration 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.
We followed up the rocker swap with an Edelbrock Performer dual-plane aluminum intake. $120
The '70 Chevelle now fitted with the Lunati rocker arms. Power measured at the rear wheels.
The Performer intake flows more air than the portly factory iron piece. Equally important is that its more modern design evens out the airflow between cylinders. Both factors lead to a nice increase in power.
Roller Rocker Arms
Lunati Voodoo 1.6:1 roller rocker arms. $338
A bone-stock '70 Chevelle SS convertible powered by an RPO L65, 9.0:1-compression 350 small-block, which came factory rated at 250 gross horsepower and 345 lb-ft of torque, running through a Turbo 350 trans. The only modification was a 21/2-inch dual exhaust system with turbo mufflers. Power measured at the rear wheels.
Some of the increase undoubtedly came from the extra lift provided by the rocker arms, but Lunati's James Humphrey told us most of the gain likely came from the decrease in valvetrain friction achieved by installing full roller rockers in place of the factory stamped-steel pieces.
The bolt-on Rocker arms and new intake in place, we replaced the Chevelle's original Quadrajet mixer with a 525-cfm Road Demon vacuum secondary carb (64/78 jets). $357
The '70 Chevelle now fitted with the Lunati rocker arms and Edelbrock intake manifold. Power measured at the rear wheels.
This was a tough one--Demon recommends its carbs for modified engines, not a factory cammed, low-compression stocker like we flogged here. Although peak gains were minimal, average power was improved through the powerband. This carb also gives us a good, easily tunable foundation to work with as more extensive modifications are made to this engine.
Doug's Headers with 15/8-inch primary tubes and 3-inch collectors. $530
The '70 Chevelle now fitted with the Lunati rocker arms, Edelbrock intake manifold, and Road Demon carb. Power measured at the rear wheels.
Our intake/carb combo got more air/fuel mixture flowing into the old Chevelle; the new headers evacuate the burnt gases much more efficiently than the factory cast-iron pieces. Another jump in power was the result.
Flowmaster Scavenger Crossover Pipe added into a Flowmaster Delta Force 3-inch dual exhaust system. $187
A '67 SS Camaro with a 10.5:1 compression 385ci stroker small-block running an Isky mechanical street roller cam, ported World Sportsman II heads, a ported Edelbrock Victor Jr. intake manifold, a 750-cfm Holley Pro series carb, and a T-56 six-speed trans. Power measured at the rear wheels.
According to our own Kevin McClelland, "The purpose of the Flowmaster Scavenger Crossover pipe is to increase the exhaust gas velocity in the large 3-inch system, providing a torque boost along with a few extra top end ponies." Looking at the numbers, that's exactly what happened.
The bolt on
Wilson Manifolds 1-inch open carb spacer. $82
A 10.2:1-compression 540ci big-block with a hydraulic roller cam spec'd out at 0.566/0.566 inch lift, 242/248 degrees duration, and 112 LSA hydraulic roller cam, along with AFR 335 CNC ported heads, a Performer RPM Air Gap manifold, and an 850 Mighty Demon carb. Power measured at the flywheel.
Open carb spacers increase plenum volume, which usually leads to increased mid-range and top-end power. That's the effect the spacer had on this engine, at the expense of the peak torque; on the other hand, average power was improved. According to Westech's Steve Brul, some combos like a spacer, some don't; you have to try it and see. This one liked it.
Hydraulic Roller Cam
Isky Retro Fit Hydraulic Roller camshaft and lifters, 0.485/0.505 inch lift (intake/exhaust), 217/225 degrees duration at 0.050, ground with a 108-degree LSA. $835
A 10.5:1-compression 350 small-block with 64cc Vortec heads, an Edelbrock Performer RPM intake, 650-cfm Holley carb, and an Isky hydraulic flat-tappet cam with 0.465 inch lift (intake and exhaust), 221 degrees duration at 0.050, and a 108-degree LSA. Power measured at the flywheel.
The specs on these two cams are very similar, but the advantages of running a hydraulic roller cam--specifically the increase in area under the curve and the reduction of frictional losses--are clearly demonstrated.
Small-Block Cylinder Heads
Brodix IK 180 aluminum cylinder heads, which have 180cc intake runners, 64cc chambers, and 2.02/1.60-inch valves. $1,014/pair
A 10.5:1, 355ci small-block with a Comp Cams XE268 cam (0.477/0.480 inch lift intake/exhaust, 224/230 degrees duration at 0.050, 110-degree LSA), ported GM double-hump iron heads, an Edelbrock Performer RPM intake, and a 750-cfm Quick Fuel double-pumper carburetor. Power measured at the flywheel.
The "IK" stands for Iron Killer, and that's exactly what happened here. You can spend your money on porting a set of old heads or spend it on a set of new heads that produces way more power.
A Granatelli Big-G Flash Tuner, which contains several performance tune configurations. It can also read and erase computer codes, modify top speed and rev limiters, alter shift timing and increase line pressure in automatic trans cars, and recalibrate the speedometer for multiple gear ratios and tire size changes. $375
The '01 Camaro SS, now with a Granatelli nitrous-tuned MAF. Power measured at the wheel.
The peak gains achieved with the performance tune are impressive, but check out the killer average improvement. This car makes more power everywhere, and you can feel it.
Mass Airflow Sensor
A Granatelli mass airflow sensor with nitrous tuning (aka nitrous meter) for use with dry nitrous systems. It works like a normal MAF during normally aspirated operation but adds 5 percent more fuel when it sees the juice. $300
An '01 Camaro SS six-speed with an SLP harmonic balancer and high-flow airbox lid, an Accufab 75mm throttle body, QTP long-tube headers with cats, GMMG chambered exhaust, and a high-pressure fuel pump.
This Camaro made good use of the increased airflow and performance calibration, and it worked well with nitrous.
An Edelbrock Perfomer GM EFI dry nitrous system set up for a 100hp shot. $570
The '01 Camaro SS, now with the ECM reprogrammed with a Granatelli Big G Flash Tuner. Power measured at the wheel.
What can we say? Nitrous is the bang- for-the-buck king of bolt-on power adders, and the torque gains here were spectacular. Also noteworthy is the fact that that Camaro made 22 more horsepower and 23 more lb-ft on the squeeze with the Big G program in place as opposed to the stock tune. CHP
GET THE HOOKUP
Barker Racing Engines
601.847.7433 · tonybarkerracingengines.com
Barry Grant Inc.
706.864.8544 · barrygrant.com
479.394.1075 · brodix.com
909.599.5955 · pertronix.com
310.781.2222 · edelbrock.com
800.544.4761 · flowmastermufflers.com
Granatelli Motor Sports
805.486.6644 · granatellimotorsports.com
Isky Racing Cams
323.770.0930 · iskycams.com
662.892.1500 · lunartipower.com
805.247.0226 · vortechsuperchargers.com
Westech Performance Group
951.685.4767 · westechperformance.com
954.771.6216 · wilsonmanifolds.com