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Rocker Arm Ratio - Power Multipliers

Rocker Arm Ratios Can Add Power

By Mike Petralia

More Ratio Also Means More Timing
As rocker ratio is increased, so, too, is valve timing. Note how changing from the stock ratio, which is actually closer to 1.46:1, to a true 1.60:1 will increase your total valve duration by almost 20 degrees! This geometric increase is true for any cam in any engine.

COMP CAMS 292H MAGNUM HYDRAULIC CAM
Degrees duration with
LOBE LIFT 1.46:1 1.60:1 DIFFERENCE
.006 289.5 291.1 +1.6
.020 273.9 276.0 +2.1
.050 253.4 256.2 +2.8
.200 188.1 195.1 +7
.400 98.6 118.1 +19.5

Rock On
The power our 383-cid Mouse gained just by bolting on a set of Comp Cams Magnum roller tip rocker arms made this whole thing worth the price of admission. The extra power and reduced heat and friction offered by the full roller Pro Magnum rockers in a 1.5:1 ratio also really makes them an attractive bolt-on.

RPM STOCK 1.52 MAGNUM 1.52 PRO MAGNUM
  TQ HP TQ HP INCREASE TQ HP INCREASE
3600 412 283 421 289 +6 417 286 +3
3800 425 308 431 312 +4 431 312 +4
4000 454 346 450 342 -4 450 343 -3
4200 463 370 466 373 +3 468 374 +4
4400 467 391 474* 397 +6 476 399 +8
4600 470* 411 473 415 +4 478* 419 +8
4800 467 427 470 430 +3 477 435 +8
5000 462 440 460 437 -3 470 448 +8
5200 452 448 454 450 +2 461 456 +8
5400 445 458 448 461 +3 458 467 +9
5600 437 466 440 469 +3 447 477 +11
5800 423 467* 427 471 +4 436 482 +15
6000 408 466 415 474* +8 423 483* +17
Avg. 445 402 449 405 +3 453 410 +8
Max* 470 467 474 474 +8 478 483 +17

Hot Rockers
The new kid on the block is definitely Hot Rockers from Everoc Industries. This unique system gives your engine the best of all rocker ratios automatically. By switching ratios as you drive, Hot Rockers gives great low-end grunt and fantastic economy along with a smooth transition to a high top-end ratio for more power. Hot Rockers have basically a full-roller, shaft-mounted design that offers stability and reduced friction at the valve tip, as well. We haven't had the chance to test Hot Rockers yet, but plan to do so soon. We'll let you know all about them in an upcoming story. Check out www.hotrocker.com to learn exactly how this ingenious system works.

Things To Check
Anytime you plan to increase the rocker arm ratio, there are several points to check.

By Mike Petralia
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