Dyno Test 1
Brulé began to install each new rocker arm into place. Since this is still a hydraulic valvetrain setup we would not need to adjust the lash. With everything buttoned up, it was time to make a pull and see the results. In this instance, we found a slight gain in horsepower and torque. We also managed to clean up the stumble in the upper rpm.
|BASELINE||PRO MAGNUM ROCKERS||GAIN|
|TIMING||42 degrees||TIMING||42 degrees||~|
|AVG HP||488||AVG HP||490||+2|
|AVG TQ||540||AVG TQ||541||+1|
|PEAK HP||566 @ 5,700||PEAK HP||568 @ 5,900||+2|
|PEAK TQ||577 @ 3,700||PEAK TQ||578 @ 3,700||+1|
Dyno Test 2
Brulé began the teardown by unbolting the intake and removing it. He then removed each lifter and replaced them with the "R" series lifters. The new lifters are a simple drop-in item and didn't alter the pushrod length whatsoever. We then installed the Ultra-Pro.
|PRO MAGNUM LIFTERS + steel rockers||GAIN|
|PEAK HP||576 @ 5,900||+10|
|PEAK TQ||580 @ 3,700||+3|
Dyno Test 3
After reviewing the results, the 496ci gained torque and horsepower. Brulé still wasn't completely satisfied though, noting "The cam should have still been able to make power up to the suggested 6,100 rpm." With that he suggested that the valvesprings may be too weak. The combination of a higher tolerance lifter and higher revving cam may be overwhelming the spring. It was then Brulé decided a spring swap and a set of titanium retainers (PN 721-16) would allow more control over the valve at high rpm. Titanium is lighter and stronger than steel, which allows for additional engine speed. Sure enough, power was up again and even helped to smooth out the entire power curve.
|DUAL SPRINGS + PRO MAGNUM LIFTERS + STEEL ROCKERS||GAIN|
|PEAK HP||579 @ 6,000||+13|
|PEAK TQ||583 @ 3,700||+6|
While our build isn't a high-budget racer, the 496ci is still seeing gains with high rpm punishment. Since the camshaft is still rated to make power up to 6,100 rpm, we needed a stiffer valvespring to handle the upper rpm. The good news is, these springs are a direct swap and do not require any additional machining to the RHS cylinder heads.
|SEAT LOAD||148 lbs @ 1.900-inch|
|OPEN||456 lbs @ 1.250-inch|
|SPRING RATE||473 lb/in|