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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- The platform for our engine was a 29-HP, 350 GM Chevy crate engine. Included among the basic dyno pieces uses in the test were a 650-CFM Holley carb, Hooker 1 3/4-inch primary tube headers, Weiand dual plane intake manifold, and HEI ignition.
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- The RHS aluminum cylinder heads were added to the base engine, a common performance upgrade for crate engines, which also reduced overall engine weight. These heads feature excellent streetable port configuration and standard 2.02-inch intake and 1.60-inch exhaust valves.
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- These RHS Pro Action cylinder heads are delivered complete with COMP Cams valve springs and retainers and feature 180cc port volume intake ports.
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- Using the new COMP Cams Ultra Gold rockers, our test two level dyno run netted 10 more peak HP and 5 more lb.-ft of torque over the ball-style rocker arms.
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- 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?
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- All three Thumpr camshafts were installed in the normal way and with lots of break-in lube. Each camshaft was also degreed to ensure that timing was consistent.
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- We noticed after the first test with the Thumpr camshaft that the engine was starved for air. A swap from the 650 to 750-CFM carburetor was a move in the right direction, as the dyno numbers would attest.
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- With all flat tappet camshafts liberal use of lubricant on the lobes prior to and during break-in is absolutely essential.
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- The Westech 902 Superflow dyno was used for all of the testing. All carburetor adjustments and jetting were made in the name of maximizing efficiency.
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- The dyno results at each level were impressive. Each Thumpr camshaft change increased the performance of the engine a significant amount and the idle became rougher as touted. An important consideration for anyone running these engines is the low amount of vacuum generated. That should only be of concern if you are running power brakes or other vacuum-assisted components. An electric vacuum pump will correct this problem if necessary.
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- 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.
Tags: comp cams, flat tappet cam, rhs heads, sbc, small block chevy, thumpr, ultra gold rockers, westech performance
