How much power are roller rockers worth? How do rockers compare to a cam swap? Can I get the same power gains with rockers and not have to tear apart the motor to replace the cam?

All good questions, so let’s take a closer look at the two.

But before we get to the rocker vs. cam test, we need to understand that there is one missing component in this discussion, and that is valve springs. In life, there are things that just go together, like Crown & Coke, peanut butter & jelly, and Batman & Robin.

Considerably less famous than the many others, we will demonstrate that valve springs are the Boy Wonder to the roller rocker and camshaft’s Caped Crusader.

Initially the combination may seem unnecessary, but rest assured, testing with either has shown the necessity of a proper spring package. Even on a stock cam, roller rockers require a spring upgrade, lest you run afoul of the evil known as valve float. Truth be told, every (high-mileage) modified LS should be treated to a valve spring upgrade, but this is especially the case when installing a performance cam or roller rocker upgrade.

Why go to all the trouble you ask? Roller rockers offer two benefits, reduced friction and (in this case) increased lift. Since we all know LS cam upgrades offer amazing power gains, think of roller rockers as portion of a cam upgrade. The gains are commensurate with the ease of installation, but roller rockers (spoiler alert) will never equal the power gains of a good cam swap.

To illustrate the actual power gains offered by both, we decided to run a test on an unsuspecting 4.8L LS!

man standing between two engines in a dyno room
Roller rockers are a natural performance upgrade for your LS motor, but how do they compare to a cam swap? (Image/Richard Holdener)

Our Valvetrain Upgrades

To compare our valve train vigilantes, we needed three things for our test motor, a camshaft, a set of roller rockers and a valve spring upgrade. For rockers, we chose a set of bolt-down Ultra-Gold rockers from the COMP ARC series. The COMP rockers (PN CCA-19024-16) offered ease of installation (simple bolt down replacement), a 1.72:1 rocker ratio to slightly increase lift (stock was 1.7), and extra strong, CNC-extruded rocker bodies that featured billet trunnions with captured needle bearings. Toss in a roller tip to replace the friction-robbing, factory slider tip and you have the makings of a serous rocker upgrade.

Knowing rockers alone weren’t enough, we combined them with a set of COMP beehive valve springs (PN CCA-26918-16). Designed as a direct replacement for the factory LS valve springs, the beehive design balanced increased spring rate (over factory) with reduced valvetrain mass (over dual springs). Though we ran our testing with the low-lift, stock cam, the 26918 springs will accept up to 0.625″ lift (more important for our BTR Stage 2 cam).

The LS Test Engine

Speaking of test motor, we had a nice little 4.8L just sitting around the shop ready for action. The rocker upgrade would be equally at home on any cathedral port, LS application, but we had the little LR4 truck motor at our disposal so we decided to give it a go. In truth, even a bone stock motor would suffice for this testing, but this LR4 had a few upgrades.

After removal from the wrecking yard, the 4.8L was treated to machine work that included boring, honing, and decking before the installation of a set of JE SRP forged pistons. The 0.010″ over slugs featured 7cc domes and were designed to work with the factory press-pin rods. The remainder of the short block included new JE rings and C77 bearings as well as Fel-Pro MLS head gaskets and ARP head studs.

The JE short block was topped with a set of stock 706 heads and the truck intake. The manifold received an Accufab throttle body, 50 pound Holley fuel injectors and matching Dominator EFI management system. Finishing things off was a Meziere electric water pump, Lucas 5w30 synthetic oil, and a set of 1-3/4 inch long-tube headers.

Valvetrain vs. Camshaft Test

The first order of business was to run the motor in stock trim to establish a baseline. Equipped with the stock cam, rockers and valve springs, the 4.8L produced 340 hp at 5,500 rpm and 346 lb.-ft. of torque at 4,600 rpm.

We then removed the coil packs, valve covers, and stock rockers to prepare for the spring swap. Truth be told, we tried the rockers with the stock springs and immediately ran into valve float. To cure the instability problem, we installed the COMP valve springs with a trick valve-spring compressor. The COMP valve spring compressor allowed us to perform the spring swap with the heads on the motor while it was still warm on the dyno. After removing the spark plugs, we applied air pressure to the cylinder to keep the valve closed then replaced the stock springs with the COMP springs.

After our spring swap, it was back to the control room to run the final test. The new COMP 26918 valve springs not only allowed us to rev the motor to 7,000 rpm without fear of valve float, they also allowed us to demonstrate to gains offered by the rocker upgrade.

You will remember that the 4.8L produced peaks of 340 hp and 346 lb-ft of torque with the stock rockers. After installation of the COMP roller rockers and 918 springs, the peak power jumped to 353 hp and 352 lb-ft of torque (see graph 1). The rocker upgrade increased the power output not just at the peak, but also showed consistent gains from 4,500 rpm to 6,500 rpm.

Obviously, the roller rocker upgrade worked, but would the gains compare to a cam swap?

To compare the gains offered by the roller rockers to a typical camshaft, we ran this same 4.8L test motor with a cam upgrade. In fact, we ran it with a number of different cams from Summit Racing, Tick, JFR, Cam Motion, and Elgin—all with similar results.

The gains illustrated here are from the folks at BTR, using their Stage 2 turbo cam, but know that cams alone can add anywhere from 25 to 30 horsepower, to over 100 horsepower depending on the rest of the combo. We put the COMP beehive springs to good use, as the BTR Stage 2 cam offered a 0.605/0.598 lift split, a 226/231 degree duration split and 113 degree LSA. Actually designed for a turbo application, this cam was maybe a tad on the big side for a 4.8L, but it showed what kind of power can be had from a simple cam swap.

After swapping in the BTR cam (with stock rockers), the power output of the 4.8L jumped to 414 hp at 6,600 rpm and 365 lb.-ft. of torque at 5,500rpm. This cam (and cams like it) improved the power output of the 4.8L by a whopping 74 horsepower. It is important to note that the power gains provided by the cam swap were most prominent higher in the rev range. (Before you ask, we did not run the BTR cam with the roller rockers, though that would have been a very cool test to add.)

Engine Dyno Graph
This graph illustrates what happens when you upgrade to 1.72 Comp roller rockers and the required 26918 valve springs. Swapping out the stock rockers in favor of the Comp 1.72 Gold roller rockers resulted in a sizable power increase. The rocker upgrade increased the power output of the 4.8L from 340 hp and 346 lb.-ft. of torque to 353 hp and 352 lb.-ft. of torque. We know LS applications respond well to cam upgrades and since the rocker upgrade increases primarily lift, think of it as part of a cam upgrade. Equipped with the roller rockers and 26918 valve springs, the motor was able to rev cleanly to 7,000 rpm. FYI, valve float occurred at 6,000 rpm with stock springs and roller rockers. (Dyno Chart/Richard Holdener)
Engine Dyno Chart Readout
If you compare the gains offered by a typical cam upgrade to the rocker test, we see the rockers added 10 to 15 hp, but this cam offered 74 hp. The gains were even greater at higher engine speeds, where the stock (mild) LR4 cam fell off rapidly. Compared out past 6,500 rpm, the gains offered by the BTR cam were nearing 100 horsepower! Of course, this cam was a tad on the big side for a 4.8L, at least for a daily driver, but ultimately you have to make a decision. Do you want to take the easy route and get minor gains with the bolt-on rockers, or do you want the Big Boy power and swap a cam (Dyno Chart/Richard Holdener)
cylinder head gasket placed on an ls engine
The test motor was an otherwise stock short block 4.8L equipped with JE forged pistons, Fel-Pro head gaskets, and ARP head studs. (Image/Richard Holdener)
ls engine on a dyno pull
Run with headers, an Accufab throttle body, and Meziere electric water pump, the nearly stock 4.8L produced peak numbers of 340 hp at 5,500 rpm and 346 lb.-ft. at 4,600 rpm. (Image/Richard Holdener)
rocker arm assemblies on a table
To compare rockers vs. a cam swap on our LS motor, we decided to install these new 1.72 ratio COMP Gold roller rockers. (Image/Richard Holdener)
rocker girdle on a table
The Comp rockers featured individual rocker stands to positively secure and orient each pair of rockers. (Image/Richard Holdener)
removing coil packs from an ls engine cylinder head
To install the new rockers, off came the factory coil packs to allow access to the valve covers. (Image/Richard Holdener)
removing valve cover of an ls engine
Next came the 8mm bolts securing the valve covers. Having valve covers and/or coil packs that allowed removal of the cover with the coil packs in place would be great here! (Image/Richard Holdener)
factory rocker arms on an ls engine cylinder head
Removal of the valve cover provided access to the stock rockers. Though the stock rockers feature a roller trunnion, there was no friction-reducing roller tip—nor did they offer the 1.72 ratio of the COMP rockers. (Image/Richard Holdener)
pair of valve springs on a blue table
To properly harness the power potential of the new rockers, we installed a set of COMP 26918 beehive valve springs. (Image/Richard Holdener)
ls engine with rockers removed
Using the COMP Cams valve spring compressor, we replaced the factory springs with the Comp 26918s. (Image/Richard Holdener)
installing rocker arms into an ls engine head
After swapping out the stock springs for the COMP 26918s, we installed the 1.72 ratio roller rockers. We made sure to properly clean and lubricate the new rockers prior to assembly. (Image/Richard Holdener)
installing valve covers onto an ls engine
We liked the fact that the COMP roller rockers bolted in place without valve cover interference. (Image/Richard Holdener)
ls engine being run on a dyno
After the spring upgrade, the motor was able to rev cleanly to 7,000 rpm. The rocker and spring upgrade increased the power output of the 4.8L from 340 hp and 346 lb.-ft. of torque to 353 hp and 352 lb.-ft. of torque. (Image/Richard Holdener)
btr camshaft in a box
Having tested the merits of the rocker swap, it was time to install a cam. This BTR Stage 2 Turbo cam offered a 0.605/0.598 lift split, a 226/231 degree duration split, and 113 degree LSA. (Image/Richard Holdener)
camshaft being installed in an ls engine
Run once again on the dyno with the BTR cam, the 4.8L produced 414 hp at 365 lb.-ft. of torque. Compared out at 6,500 rpm, the cammed 4.8L was making an extra 100 horsepower. (Image/Richard Holdener)
Summit Racing camshaft in box on table
Truth be told, we ran the 4.8L with a number of different cams during testing. Not surprisingly, cams with similar specs, like this 8720 camshaft from Summit Racing offered similar power gains. Cam swaps might be more difficult and expensive than rocker upgrades, but you get what you pay for—meaning the power gains are also much more significant. (Image/Richard Holdener)

Keywords
camshaft, rockers, roller rockers, valvetrain tech
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Author: Richard Holdener

Richard Holdener is a technical editor with over 25 years of hands-on experience in the automotive industry. He's authored several books on performance engine building and written numerous articles for publications like Hot Rod, Car Craft, Super Chevy, Power & Performance, GM High Tech, and many others.