COMP’s new Thumpr™ line of camshafts makes power, and they aren’t subtle about it
“You hit home runs not by chance, but by preparation.” – Baseball great Roger Maris
Great advancements come at the intersection of inspiration and need. Thermal underwear, for example, sells a lot better in Minnesota than Florida. Lots of people have great ideas but are unable to find anybody who wants them. The trick is to find out the needs of the people, and then match the inspiration.
Tim Cole from COMP Cams®
“We’ve interviewed hundreds of people at car shows and speed shops,” said Tim Cole from COMP Cams®. “These were all people who were thinking about or in the process of buying a camshaft for their cars. They were going to buy a new camshaft, and we found out that they had two main criteria. Number one was better performance. That one was obvious. And number two, they told us they wanted the cam to make their car sound downright mean. These were the overwhelming responses that we got.”
“So we had the information that we had gathered from talking to people, but then we had an experience that really set things into motion. At one of the car shows a customer was talking to a member of our team and he said, ‘I want you to build me a cam, and I want that mother to thump.’ And that’s when the light went off. That’s what started it all.”
And that was the birth of the Thumpr™ family of camshafts.
Thumpr™ Cams are designed to deliver the rough, racy exhaust note associated with big, carbureted race engines. But they are also quite different. The problem with all-out race cams is they are designed expressly for one purpose. They may run like a scalded dog at high rpm levels, but they can also be miserable to live with on the street. Acceleration from idle and behavior at lower rpm levels can be notoriously poor.
A Thumpr™ Cam, however, is designed to provide the rough, racy sound of a race cam with better drivability. That makes it perfect for gearheads that want their cars to sound as good as they run - everywhere. That means you can have a lumpy, intimidating idle and still drive your car to work every day. Or better yet, cruise night or car shows or church on Sunday morning.
Just ask Lee Watson, one of the first people to put a Thumpr™ in his car. “I have a ’32 Ford three-window Highboy Coupe. It had the 350 horsepower Chevy 350 crate motor in it, and I was looking for a different camshaft to put in it,” he says. “I’m also involved in drag racing, so I knew COMP Cams and Tim Cole, and he told me about these new Thumpr Cams. So I installed one, along with a set of roller rockers.
“And I love it. The cam sounds great, and it’s got both low-end and top-end power. Everybody that hears my car says, ‘Man, that’s badass!’ It’s just a really nice cam.”
Normally, drivability is built into a camshaft by building in good low-end torque. This means optimizing the camshaft to work better at lower rpm levels by shortening up the duration (the amount of time the cam holds either the intake or exhaust valves open) and reducing the amount of overlap (the period when the cam has the exhaust valve closing and the intake valve opening at the same time). But this also makes a motor quieter by keeping the exhaust valve closed longer. A Thumpr™, however, breaks the rules and does it successfully by enhancing the exhaust note while maintaining driveability.
“The Thumpr Cams aren’t designed around lobes we just pulled out of the catalog,” Cole explains. “They had to be specially designed to meet our performance goals. With the Thumpr Cams we increased the amount of overlap, because the exhaust side of the event is what you hear. By increasing that overlap window, we achieved that great sound.
“But we didn’t just increase the overlap in the lobe designs and call it a day,” he continues. “The Thumpr Cams are also ground on a narrow 107-degree lobe separation. For comparison, most of our popular Xtreme Energy Cams are ground with a 110-plus degree lobe separation angle. The cams are also ground with five degrees of advance in them, putting the intake centerline at 102 degrees which puts a lot of torque back into the motor that the increased duration would try to water down in the normal world. These lobe designs are popular in thin air and summertime applications. Customers in Denver love the Thumpr Cams; because the things we do to make them work are the same things we do to make a cam work at high altitude anyway.”
Watson says that the increase in torque is something you can definitely feel in the seat of your pants. “My street rod has a high 3.0 gear in the rear end. I can step on the loud pedal, and it will carry the left-front wheel through the intersection. So it has definitely got the performance to back up the sound. It’s not all show and no go.
“But it also idles down to 700 rpm,” he adds. “I’ve got air conditioning in the car and the whole business. It makes plenty of vacuum. I just took the cam out of the box and shoved it in, and I’ve been driving it ever since.”
Currently, COMP® offers the Thumpr™ Cams in three different levels in increasingly radical grinds. The baseline is the Thumpr™ for smaller or more basic engines. For Chevy Small Blocks Thumpr™ Cams are the most popular option. Thumpr™ Cams also usually work well with OEM valve train components so that the costs of upgrading are minimized. While the duration is increased, the lobes are still gentle on valves and springs so that the increased performance doesn’t result in your valve train flying apart. Total valve lift is also held in check to keep shorter stock springs out of coil bind. Cole says that when the displacement ramps up toward 383 and 406 cubic inches, they become candidates for the next level, the Mutha' Thumpr™. In small blocks, the most extreme level, the Big Mutha Thumpr™, is best reserved for street/strip cars that spend more time on the strip than the street. As Cole says, “The Big Mutha' Thumpr is a really serious cam in a small block; it’s not for the faint of heart.”
But if you are looking to stuff a Thumpr™ Cam in your big block engine, the extra cubes make the standard Thumpr™ a bit tamer. Many big block owners choose to go with the Mutha' Thumpr™ which can handle a more radical lobe design without a problem.
These numbers show not only performance, but the mighty “Thumpr™” sound too.
The result is that, no matter what carbureted engine you run, you have options available. COMP® now has Thumpr™ designs in all three levels available for most makes and sizes of V8 engines. Lobe designs are available to work with both hydraulic flat tappet lifters as well as hydraulic rollers.
So if you already have a hydraulic roller cam, you can save some bucks by reusing your roller lifters. That means the choice is up to you. All three levels of Thumpr™ Cams increase power over stock cams, so the real choice is how much “thump” do you want from your engine? One of the best ways to get a feel for how each level of Thumpr™ Cam sounds is to go to the COMP Cams® website and check out the information section on the Thumpr™ lineup. There you will find recordings of engines with each level of camshaft so you can hear for your own ears the incredible rumble they make. So now, as Cole says, a Thumpr™ Cam will let you have both the sound and the fury.
Check Out the Available Thumpr™ Cam Kits
The Thumpr™ CL Kit includes: cam, lifters, assembly lube, decal and instructions.
The Thumpr™ GK Kit includes: cam, lifters, gear drive, assembly lube, decal and instructions.
The Thumpr™ K Kit includes: cam, lifters, valve springs, retainers, valve locks, valve stem seals, timing chain set, assembly lube, decals and instructions.
Engine: 350cid, 290 hp, GM Crate Engine
Cylinder Heads: RHS™ 180cc Runners, 64cc Chambers (Assembly) #12023-01
Lifters: COMP Cams® High Energy™ Hydraulic Flat Tappets #812-16
Rocker Arms: COMP Cams® Magnum 1.52 Ratio #1412-16
Manifold: Weiand Dual Plane
Carburetor: 750 Holly HP (Thumpr™) – 650 Holley HP (Stock Cam)
Headers: 1 ¾” Hooker Headers
Mufflers: Magnum Race Mufflers & 18” Extensions
Ignition: Stock HEI Distributor
*Unless noted above all components stock
Take a look at these links see the performance and hear the sound of the Thumpr™.