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Pettis Performance 598ci Big-Block - Big, Wild, & Nasty Part twoOur Pettis 598ci Cranks Out 1,120 hp-Without Nitrous! From the June, 2010 issue of Chevy High Performance By Michael Galimi Photography by Henry De Los Santos
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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 Performance mocked... Pettis Performance mocked up the engine several times and made many modifications before its final assembly and engine dyno testing. Up front, the Jesel front drive distributor and beltdrive system are essential for timing accuracy and quick cam timing adjustments. The oil pan of choice is a Moroso unit with their external wet-sump setup. 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.  A BHJ cutting tool was used...  A BHJ cutting tool was used to add an O-ring in the block and a receiver groove in the head. Pettis said he prefers to add the ring in the block because if the head ever needs to be repaired it is one less modification required. The deck rarely gets re-cut over time, which is why he prefers to have the O-ring in there. A 0.041-inch thick ring is used to help seal the heads to the block.  The Edelbrock Victor/Musi...  The Edelbrock Victor/Musi CNC 24-degree heads were inspected and modified for this application. Pettis Performance opened the intake ports slightly, performed a valve job, added larger intake valves, and modified the exhaust ports. Overall, Pettis was very impressed with these cylinder heads and its capabilities.  Edelbrock sent the heads with...  Edelbrock sent the heads with a CNC port job and Pettis added Ferrea 2.350-inch intake valves and 1.900-inch exhaust valves. The combustion chamber checks into the party at 114 cc.  Hogan's Racing Manifolds builds...  Hogan's Racing Manifolds builds each sheetmetal manifold as a custom piece. For ours, we downloaded a template, which asks for very specific dimensions, including cubic inches, deck height, chassis weight, compression, along with whether it's an EFI or carbureted application. Once completed, we submit the information and were very pleased with the quick turnaround time.  The heads received a 50-degree...  The heads received a 50-degree seat and as Pettis explained, the steeper valve seats improves flow on some heads, with the Edelbrock Victor 24-degree being one of them. Seats are cut on a Newen GII CNC machine using custom cutters designed by Pettis with CAD software furnished by Newen. The cutter is labeled with a serial number that is recorded on the engine blueprint sheet.  Valvetrain stability is one...  Valvetrain stability is one of the key elements that Pettis performs on these racing engines. An often overlooked part of valvetrain stability is how the rocker stands fit on the cylinder heads. The shop custom fits the stands to each head to ensure proper fit and clearance.  Pettis welded the intake and...  Pettis welded the intake and exhaust rocker stands together to form a stronger foundation. The stands also needed to be milled down and adjusted for the ultimate fitment. Pettis commented that these are built to fit wide applications and he just custom fits them to what each engine requires.  You see where the stand now...  You see where the stand now has a step cut into its base to clear the top of the head bolt. It's small details like this that has put Pettis Performance on top, churning out record-breaking and championship-winning powerplants for dozens of racers in serious heads-up organizations.
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