Theory To The Test

We were curious about these new cams from COMP. While conceptually we could accept the difference in runner length and position would have an effect on cylinder-to-cylinder requirements, we were not sure what could be done about it. After all, we had to wonder whether a camshaft could compensate for air/fuel ratio, air speed, and wave tuning inconsistencies. Our test engine was a 372-cube Dart SHP short-block topped with a set of AFR 195cc Eliminator heads. These Eliminator heads featured AFR’s well-developed combination of moving parts, including their lightweight valves, titanium retainers, and lightweight springs for exceptional high rpm performance with a hydraulic roller cam. With this test engine we did not expect valvetrain instability to curb either cam short of its maximum potential.

To gauge air/fuel ratios, we bolted on a set of specially prepared dyno headers with lambda sensor bungs in each pipe. The O2 sensors worked with the electronics from Daytona Sensors to give a reading of the mixture from each hole. Our small-block Chevy was fitted with a Holley Strip Dominator single-plane intake manifold and Holley’s hot 750 Ultra HP aluminum-bodied carb. First up was the COMP XR294HR cam as our baseline. This cam is a member of COMP’s Xtreme Energy line of hydraulic roller cams, the standard of the industry for performance hydraulic rollers. As expected, the engine performed flawlessly, pulling solidly to 7,000 rpm to set our baseline numbers of 473 lb-ft of torque at 5,300-5,400 rpm and 527 hp at 6,500-6,600 rpm. The Xtreme Energy cam set a mark that would be hard to beat.

Thanks to the COMP two-piece aluminum timing cover, we had the new 4-Pattern cam stabbed in our small-block Chevy in a matter of minutes. This stick featured more lift with virtually identical duration by virtue of its more modern lobes, plus the unique valve timing strategy of the 4-Pattern. Pulling it to the redline showed an overall increase in power throughout our test range from 3,100 to 7,000 rpm, with a substantial gain in torque production through the low and midrange. Scrutinizing the individual cylinder lambda readings from our Daytona Sensors system, we found the cam did improve the air/fuel distribution, tightening the ratio variance by 0.11 ratio points between the inside and outside cylinders. With more power and more even flow into each hole, our COMP 4-Pattern cam lets each of our eight cylinders work to their potential.

BY THE NUMBERS

COMP XR294HR VERSUS CS293QIO8
Camshaft:XR294CS293*
Duration intake at .006:294293/295
Duration exhaust at .006:300305/307
Duration intake at .050:242241/243
Duration exhaust at .050:248251/253
Lobe lift, intake:0.36.398/.399
Lobe lift, exhaust:0.375.389/.389
Gross intake lift with 1.6:1 rocker:0.576.637/.638
Gross exhaust lift with .6:1 rocker:0.6.622/.622
Lobe separation angle:110107.5/108.5
Recommended installed intake centerline:106102/103
Intake opening at .006:41 BTDC43/43 BTDC
Intake closing at .006:73 ABDC70/72 ABDC
Exhaust opening at .006:84 BBDC84/86 BBDC
Exhaust closing at .006:36 ATDC41/41 ATDC

ON THE DYNO

COMP 4-PATTERN CS293 VERSUS XR294 372 SMALL-BLOCK CHEVY TEST ENGINE
RPM:TQ XR294:TQ CS293:HP XR294:HP CS293:
3,100410422242249
3,200409420249256
3,300410419258263
3,400413420267272
3,500416423277282
3,600421427288293
3,700425432299304
3,800429436311316
3,900433440322327
4,000437445333339
4,100442449345351
4,200447454357363
4,300451459369376
4,400455463381388
4,500458467393400
4,600461469404411
4,700463471415422
4,800466473426433
4,900467475436443
5,000469477447454
5,100471478457464
5,200472479468474
5,300473479478483
5,400473478486491
5,500470475493497
5,600467472498503
5,700463467503507
5,800459463507512
5,900455459511515
6,000451454515519
6,100447450519523
6,200442445522525
6,300437439524527
6,400431433526527
6,500425427527528
6,600419420527528
6,700412414526528
6,800404407524527
6,900396400521525
7,000388390518520

SOURCE
Air Flow Research
28611 W. Industry Drive
Valencia
CA  91355
661-257-8124
http://www.airflowresearch.com
Comp Cams
3406 Democrat Rd
Memphis
TN  38118
800-999-0853
www.compcams.com
Daytona Sensors
386-322-7390
www.daytona-sensors.com
Dart Machinery
248-362-1188
www.dartheads.com