This is a great time to be an engine tech geek. A few months ago we introduced a dyno test of one camshaft that is part of a new line of camshafts that COMP Cams’ Director of Valvetrain Development calls the Low Shock Technology (LST). You can check out the introductory story here. This new lineup of lobes was developed for the larger cam journal diameters of the GM LS and Chrysler Gen III Hemi families of engines.
We’ve covered the details on how cool these new LST lobes are at offering both a power gain along with increased durability — but the expanded news here is that COMP now offers similar lobes that can work with the smaller journal diameters of other engine families including the small- and big-block Chevys. There are a ton of details to cover so let’s get started.
We first learned about the benefits of the LST-style lobes when we performed the aforementioned test at Westech using a 404ci LS engine. If you want all the killer details you can check them out here, but the highlights are that we started with a 281LRR-lobed hydraulic roller camshaft that is considered an excellent street performance cam. The specs on the cam were 231/247 degrees at 0.050-inch duration with a lift of 0.617 inch/0.624 inch and a 113-degree lobe separation angle.
After establishing baseline power, we swapped this cam for a new COMP LST version with specs that were nearly identical. The new cam checked in with 231/244 degrees at .050 with 0.614 inch/0.606-inch lift with a 115.5 degree LSA. The only other change was to add COMP’s recommended dual valve springs. Any experienced performance engine builder would expect very little power difference between these two cams based on their specs. Despite appearances, the LST lobe design delivered a 16-horsepower improvement over the previous cam with a power increase at every data point above 4,000 rpm. Frankly, we were more than a little surprised.
Mechanics of More Power
Now let’s get into exactly what drove this new line of cam development along with how these new lobes are able to improve power. It all comes down to managing the valvetrain while adding improvements to both power and durability. Stick with us as this is a deep dive into how engines make power.
Let’s start with how a lobe design tweak can increase power. EngineLabs readers may recall a project that involved Godbold and EFI University’s Ben Strader called Project Spinal Tap. That 11,000 rpm effort pointed to some interesting approaches to lobe design that Godbold used to create the LST family.
LST Lobe Families
MGZ, MGH, MBZ, LPM, LSD, XLD & LSO
Endurance Solid Rollers
LGW, LGA, LIH, LHW, LXW, LDW, LKD, LXE
Drag Race Solid Rollers
LMS, LMX, MMO, MMX, OLM, MBW, MST, MJN, MJW, MJO, MDW, MNP, MFP, MTW, MSL, LXC, MSM
While this approach made power, it was also abusive to valvesprings. For drag racers, they might get 10-20 passes on a spring before it lost enough load that replacement was required. Godbold’s idea was to slow the initial opening side down and not hit the valvespring as hard. That would minimize what was often seen as a huge dynamic wave that would travel through the spring during the valve opening and closing event. With this new design, the spring could now use more of its natural load to control the inertial forces of the valve at high RPM instead of sharing that load to control the massive wave surges traveling through the spring itself.
To make up for this slower initial ramp, Godbold then enhanced the acceleration in the middle of the curve with special attention paid to the closing side. As Godbold explains, there is very little airflow occurring at the initial intake valve opening because the piston has just moved past TDC. However, on the intake closing side (as the piston is moving upward) there is the potential to move additional airflow into the cylinder using the inertial ram effect of the high-velocity air moving past the intake valve, despite the fact that the piston is moving upward.
If additional lift is generated on this closing side, the cylinder will eventually trap more air after the intake valve closes. This will make more power. This is exactly what the LST cam lobe design accomplishes, while at the same time, offering improved valve control that also may not require as much valvespring load. The resulting lighter spring loads reduce strain on the valvetrain, which in turn, means everything will last longer.
Applying Science to Other Cam Families
This is what we saw with the LST cam test on that 404ci LS engine and what prompted us to look into similar lobe designs that might be available for engines beyond the Gen III/IV engine family. While our examples will concentrate on the small- and big-block Chevy, the same approach can be taken with virtually any engine that can accept the accompanying LST-style lobe families.
We’ve also included a list of journal diameters for popular engines. There are certain specific requirements you need to know that are necessary to ensure the cam will work in your engine. We won’t get into those details here, but they are outlined in COMP’s Master Lobe Catalog. If you have questions, the best place to get answers would be to call COMP’s Tech Line, directly.
Cam Journal Diameters
|SB Chevy||BB Chevy||50mm||SB Ford||BB Ford||LS / 55mm||60mm|
Given this, Godbold suggests that if you would like to try an LST family lobe, that you can choose a lobe with perhaps 1 to 2 degrees more advertised duration. Plus, what we’ve discovered is several lobe families offer significantly more lift for the same duration at the 0.050-inch tappet lift numbers.
Using a small-block Chevy as an example, we have a 383ci small-block that uses Comp’s Xtreme Energy roller with the specs listed in the small-block Cam Specs chart. To replace the existing cam, Godbold suggested the MGZ family for the intake side and ESX for the exhaust side. Each family of lobes offers multiple durations at 0.050. We chose a lobe with a slightly longer advertised duration of 296 while the duration at 0.050 number was only one degree longer with 237 degrees versus 236 for the Xtreme Energy cam.
SBC Example Camshaft Specs
Existing Hydraulic Roller Cam 357ci SBC
Xtreme Energy XR288HR
Adv. Dur. Lift LSA Adv. Lobe
Dur. 0.050 (inches) Lift
I – 288 236 0.520 110 4 0.347
Ex – 294 242 0.540
383 – LST Custom Cam – MGZ intake and ESX exhaust lobes
33396S Intake Lobe / 33701S Exhaust Lobe 33396S / 33701S HR112 4
Adv. Dur. Lift LSA Adv. Lobe
Dur. 0.050 (inches) Lift
Int. – 296 238 0.585 112 4 0.390
Exh. – 308 249 0.585 0.390
MGZ Lobe Family
This is a selection of several different MGZ lobes that are part of the Low Shock Technology family of intake lobes. This particular section features a lobe lift of 0.373-inch.
|Lobe Number||Duration at 0.006||Duration at 0.050||Duration 0.0200||Lobe Lift||Theoretical Valve Lift at Rocker Ratio|
The combination of those benefits from the LST cam improved power on our LS engine by more than 16 horsepower and our LS engine test did not increase valve lift. If the heads on your engine can accommodate the additional airflow, this could easily be worth 20 horsepower — or more — on a good, large displacement small-block.
One advantage to the low-shock lobes is that they also respond very positively to adding rocker ratio. Our existing small-block is using the 1.5:1 rocker ratio and a shift to a 1.6:1 ratio would improve the valve lift across the entire lift curve. This likely will not be necessary with the additional valve lift generated by the new MGZ lobe but if your engine can accept the additional lift, this could push the maximum valve lift to 0.624-inch! That is big-block Chevy territory.
Going Bigger Than Big
Speaking of big blocks, let’s address the Rat motor using a 496ci stroker with a mechanical roller cam as an example. In the Comp catalog, this engine’s cam is listed as a circle track cam with the specs listed in Chart 5. This is a big cam with 261 degrees at 0.050 using a COMP RX intake and RZ exhaust lobes.
Godbold suggested the LGW / LGX mechanical roller low-shock lobes as an upgrade. Looking through the specs of those two lobe families, we found an intake lobe that was very close in 0.050-inch duration numbers. This added 1 degree to the advertised duration and had actually slightly less intake valve lift, which was already very tight on piston-to-valve clearance. However, with the additional area under the curve on closing, this promised a slight power increase.
Big-Block Chevy Mechanical Roller Cam Specs
294RX-8 PN 11-851-9
Adv. Dur. Lift LSA Lash
Dur. 0.050 (inches) (inches)
I – 294 261 0.734 108 0.020
Ex- 303 270 0.737 0.022
This cam uses an RX Intake Lobe and RZ Exhaust Lobe
LST lobes – LGW intake and LGX exhaust custom cam recommendation
Adv. Dur. Lift LSA Lash Lobe
Dur. 0.050 (inch) (inches)
Int. 295 264 0.717 111 0.014”* 23327
Ex-303 272 0714 0.016”* 23375
By widening the lobe separation angle, this will automatically retard the intake lobe centerline and increase the piston-to-valve clearance. Because this is difficult to estimate, any new lobe selection here might be best enhanced with a discussion with a COMP tech representative in order to make sure the cam will work in the engine. This is worth emphasizing since too aggressive of a lobe selection could result in piston-to-valve interference which would then require machining the valve reliefs and a loss of compression.
But again, the advantages of this move are significant with the potential increase in cylinder pressure. This particular 496 had already been dyno tested with the original cam at 707 hp. The original LST test on the 404ci LS engine increased power by 16 horsepower or nearly four percent. A four-percent gain would mean as much as a 25 horsepower bump with our 496. That would put this big block over 730 peak horsepower, which would be outstanding.
Another advantage in favor of the low-shock family of lobes is that not only is there a horsepower gain, but often valvespring life will also see a major improvement. This is based on the reduction in stresses imparted into the valve spring thanks to the softer initial acceleration of the valvetrain. Godbold has seen this on Comp’s Spintron, where, after extensive testing, the springs exhibit only a slight loss in pressure, which means the springs are happier and will last longer.
A final thought from Godbold emphasized that dyno tests do not tell the whole story. Early reports from road race and street applications are that the LST cam family also contributes to improved throttle response, as well. The bottom line is that this new Low-Shock Technology approach offers the double-barrel advantage of not only more power but at the same time improving valvetrain durability, and it’s not just for the LS and Gen-III Hemi families of engines. This truly is the Golden Age of Horsepower, especially when you know where the good parts are stashed!