A New Beat – A Simple Camshaft Swap Creates Increased Power and Unique Sound

June 10th, 2010

COMP Cams’ new Thumpr flat tappet camshafts come in three levels of performance. As you might expect, the base performance cam is called the Thumpr, followed by the more aggressive Mutha Thumpr and the red hot Big Mutha Thumpr. Pretty creative, huh?

So, the question arises with regard to camshafts, “Can you have your cake and eat it, too?”  In the case of our dyno test, we wanted to know if there was a camshaft that not only delivered on the dyno, but would enhance the sound of power derived from our engine for cruise appeal.

The COMP Cams Thumpr camshaft line of roller hydraulic camshafts, introduced in 2006, have been a huge success, well beyond their original sales estimations. For the uninformed, the Thumpr camshafts, which are available in three different sizes: from the Thumpr and Mutha Thumpr all the way up to the Big Mutha Thumpr. They are designed not only to provide good power and torque from your small- and big-block Chevy, small-block Ford and small-block Chrysler engines, but through careful specification modifications tremendous high performance sound, too. For folks looking for a hot-performing camshaft that delivers great performance and wild camshaft idle, the Thumpr cams could be the right call.

But while the roller camshaft application may be the best choice for many, roller systems are more costly than the early, more common flat tappet configuration used by Chevrolet in small-block Chevy engines through 1987.  COMP Cams has the solution for this as well with their new line of flat tappet Thumpr camshafts. Again, three different profiles are offered, each increasing the performance emitted. These camshafts are simple drop-in units that do not require any other engine modifications except for a quick assessment of valve spring condition, as would be the case with any camshaft swap. Standard hydraulic flat tappet lifters are used along with standard rocker arms and other valve train gear.

How Does It Do That?

The basic science behind the Thumpr cams is not a new one. The Thumpr line delivers true high-performance engine sound by “tightening” the lobe separation angle of the camshaft. This creates more overlap between exhaust and intake events and more “cool” performance sound. Pretty simple science, and while logic would have you believe that power is lost due to this overlap, our results have shown performance is actually up over similar camshafts due to COMP Cams’ innovative lobe designs. And the public reaction has been overwhelmingly positive.

To test the real power found with these camshafts we enlisted the folks at Westech Performance to take the new flat tappet camshafts and compare them head-to-head with the stock 350-CID, 290-HP GM crate engine and an Xtreme Energy COMP Cams cam with similar performance specifications to these Thumpr camshafts (actually it fits between the middle and largest camshaft in the line).

The results of our tests prove the mettle of the Thumpr cams, great power and torque, and neither component was compromised in the quest for great performance sound. If there is one area to note, it is the engine vacuum readings from the Thumpr-equipped engines. While the Xtreme Energy camshaft showed a reduction in vacuum generated, the Thumpr camshafts were slightly more reduced and under the 16 inches of vacuum recommended for engine driving power accessories, such as power brakes, where vacuum is critical to safe operation. The fix is to invest in the COMP Cams electric vacuum pump that will ensure at least 18-22 inches of vacuum. This electrical pump is simple to install and only operates when vacuum drops below 18 inches.

If cool is the rule on the street, COMP Cams’ new flat tappet Thumpr cams are most certain to rule and continue the legacy begun by its hydraulic roller camshaft cousins.

Thumpr Flat Tappet Camshafts Currently Available

Small-Block Chevrolet: 1955-98 model years, 262-400-CID

Small-Block Chevrolet: 1987-98 model years, OE hydraulic roller-equipped

Big-Block Chevrolet: 1965-96 model years, 396-454-CID

Small-Block Ford Windsor: 1969-95 model years, 221-351W

Small-Block Mopar 1964-2000 model years, 273–360-CID

The dyno curves paint a picture of significant power improvement. Our base engine peak numbers were 318 HP and 355 lb.-ft. of torque. With the Big Mutha Thumpr and a host of other bolt-on changes, the final peak numbers were 381 HP and 387 lb.-ft. of torque.

COMP Cams Flat Tappet Thumpr Camshafts and Rocker Arm Comparisons

Westech Performance – Mira Loma, CA

The following tests were run with the COMP Cams new flat tappet Thumpr camshaft on the Westech dyno over three days in late December.  The base engine was a time-tested 350-CID 290-HP small- block GM crate engine featuring a Weiand Air Strike intake manifold, 650-CFM Holley carb, Hedman 1 3/4-inch primary tube headers, Magnum mufflers with 18-inch collector extensions, and an HEI distributor system.  The dyno test was run through a range of 2,600 to 6,000 RPM. For each configuration several tuning tests were completed, with the three best pulls averaged together to create a fair representation of the engine’s power and torque.

Baseline Peak Power

315 HP

353 lb.-ft. torque

2,600-6,000 RPM Range Test

Average Power: 264 HP

Torque: 325.5

Vacuum Noted: 15 inches

Test one included a cylinder head swap using the RHS heads delivered to Westech Performance. These are the as-cast, complete heads ready to bolt on with valve springs compatible with the flat tappet Thumpr tests to be performed. The stock ball-style rocker arms were used for this test.

Peak Power

318 HP

355 lb.-ft. torque

Average Power: 265.9

Torque: 327.7 lb.-ft.

Vacuum Noted: 15 inches

Test two involved the same engine with a change to the COMP Cams Ultra Gold Aluminum rocker arms. The ratio used was 1.5:1, the most common ratio to be found with small-block Chevy engines of this generation.

Peak Power

328.8 HP

360.9 lb.-ft. torque

Average Power: 269.6

Torque: 332.4

Vacuum Noted: 15 nches

Test three involved the use of the COMP Cams Magnum roller tip and ball-style rockers. The same 1.5:1 rocker ratio was used. The results of the dyno tests were as follows.

Peak Power

324.5 HP

358 lb.-ft. torque

Average Power: 269.1

Torque: 331.2 lb.-ft.

Vacuum Noted: 15 inches

Test four involved the use of the first of the Thumpr flat tappet camshafts. Starting with the smallest of the three camshafts, Steve installed the 279T unit. The Magnum rockers were used for this and all tests to come.

Peak Power

341 HP

376 lb.-ft. torque

Average Power: 285.1

Torque: 351.5

Vacuum Noted: 9 inches

In testing, Steve noted that the engine was carburetion challenged. To fix that problem, he installed a 750-CFM carb and tuned it appropriately. The 750-CFM carburetor was left on for all subsequent tests. The new results with the 279T Thumpr cam were significant.

Peak Power

357 HP

387 lb.-ft. torque

Average Power: 292.4

Torque: 358.9

Vacuum Noted: 9 inches

The midrange Thumpr camshaft was tested next: P/N 287T. All other parts were the same as the previous test, including the 750-CFM carb and Magnum 1.5:1 ratio rocker arms.

Peak Power

376 HP

393 lb.-ft. torque

Average Power: 299.5

Torque: 365.6

Vacuum Noted: 7.5 inches

The final Thumpr test was performed with the 295T camshaft. Again, all parts as the previous two Thumpr tests were retained.

Peak Power

390 HP

395 lb.-ft. torque

Average Power: 302.9

Torque: 368.3

Vacuum Noted: 5.5 inches

The final test of the session was conducted with the COMP Cams Xtreme Energy XE284 camshaft featuring similar dimensions as those to be found with the Thumpr 295T camshaft. The same parts and setup used in the previous tests were used again.

Peak Power

381 HP

387 lb.-ft. torque

Average Power: 297.8

Torque: 363.5 lb.-ft.

Vacuum Noted: 8.2 inches

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