Pettis Performance 598ci Big-Block - Big, Wild, & Nasty Part two

Last month we embarked on a mission to build a big, wild, and nasty big-block engine to compete in the West Coast radial tire ranks. It is a class reserved for rowdy engine combinations stuffed under the hoods of ordinary stock-suspension equipped cars that roll on 275/60-15 drag radials in the back. Fierce competition has pushed this heads-up eliminator into the 7-second zone forcing our editor, Henry De Los Santos, and his racing partner, Artis Houston, to step up their game. The plan was to build a 598ci engine that fits with the 3,300-pound minimum vehicle weight they are shooting for, which takes into account the Hogan's sheetmetal intake and the conventional-style Edelbrock Victor 24-degree cylinder heads.

The LA-based group of racers showed up on the doorstep of Pettis Performance (Hesperia, California), where Jason Pettis and his capable staff filled in the details and built a powerful combination. The ever-determined race shop sought 1,100 hp and 8,800 rpm from this engine in order for the team to contend for the title. Pettis' goals for this engine combination were quite lofty, especially since the cylinder heads weren't of the Pro Stock origin like a set of Big Chief or other unconventional race-style heads. The Edelbrock Victor/Musi CNC 24-degree cylinder heads are considered a conventional set of heads, but they have race-style features like generous valve sizing and healthy port size and flow.

Pettis only had to make a few modifications to the out-of-the-box heads. "All we did was add a larger intake valve and increase the cross section of the intake ports. Edelbrock did a great job out of the box," he said. "We did increase the runner volume of the exhaust ports due to the nitrous. The reason for that is a nitrous motor has a larger exhaust gas volume than a naturally aspirated engine because of all the extra fuel. The exhaust gas is also hotter, so there has to be more volume to allow it to expand. Another reason for the port volume is that the bigger motor requires bigger ports to achieve the rpm levels we were shooting for."

The goal with this massive 598ci bullet was 8,800 rpm, a lofty one but that rpm range was needed in order to keep up with the quick blower and turbo combinations that are taking over the Wild Street category. You could hear the enthusiasm in Pettis' voice, "I was impressed with how this combination worked with the cubes and it went right to 8,800 rpm. With the correct intake and cam, these heads would work great even on a 632! Sure, a Big Chief or other spread-port head would outperform it, but this is a 24-degree head."

It takes more than a great set of cylinder heads to turn serious rpm and make over 1,100 hp on the dyno. Pettis explained, "the intake has to have enough runner cross section and plenum volume to support the 598ci." Hogan Intakes built a custom sheetmetal intake based on the target hp range of this bullet. It wears two Holley HP series 1050 Dominator carburetors that were dialed in on the engine dyno. The cam is top-secret but Pettis did admit to lift numbers of 0.950-inch for the intake and 0.900-inch lift on the exhaust lobes. "The valvetrain is the biggest key for a high-rpm combo, the 4.500-inch stroke isn't that big of a deal," commented Pettis. The team relies on Jesel rocker arms and lifters as well as super-thick Manton pushrods. Valvetrain stability can be directed back to the small details, one of the biggest is the way the Pettis Performance shop sets it all up on the heads. Pettis spent some time working the heads and the rocker stands to his liking, namely to ensure a solid foundation. The Jesel rocker arms are also longer and feature a roller-bearing wheel tip.