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.
The short-block was built to endure rpm and a fury of nitrous induced horsepower. Last month, we showed how a Dart Big M block was filled with a Kellogg crankshaft (4.500-inch stroke), JE custom pistons (13.6:1 compression), and GRP rods. The Dart Big M block is made of iron, providing stability to keep the cylinder bores from moving around and that means better ring seal. It was modified with 4.600-inch bores and Pettis moved the lifter bores in order to straighten the pushrod angle and prevent them from intruding on the intake port. The pistons went through a barrage of modifications from tension tests with its rings and modified domes for the valve layout of these heads. The short-block and ultimately the entire long-block were assembled and disassembled several times as Pettis checked every moving part for proper clearances and fitment.
On the dyno, the Pettis 598ci didn't disappoint as it spun all the way up to 8,800 rpm without any trouble at all. The heads, intake, and valvetrain performed admirably and the final numbers are a stout 1,120 hp at 8,000 rpm. On the torque side, Pettis began the power sampling at 6,500 rpm so the only peak torque number he has is 810 lb-ft at the bottom of the pull (6,500 rpm). Peak torque probably occurs closer to 6,200 but since the engine will never run that low there is no reason to test its power output there.
Pettis dissected the dyno results, "I look at the average in a 1,200 or 1,300 rpm spread, which is the optimum range of the motor with the torque converter. This engine made 1,102 average from 7,200 to 8,500." He continued, "it doesn't fall off and will run real hard on track." Pettis did explain that this engine could have much more power if they set it up for naturally aspirated trim. But nitrous oxide injection is in the future for this beast. "It makes great power despite only having 13.6:1 compression and the pistons sitting 0.040-inch below the deck," he stated. The piston location below deck is not good for quench as it slows down the burn-rate of the fuel, which is good for use with nitrous but bad for making power in naturally aspirated trim. Au naturel engines require the fuel to burn quickly to make power. Another noteworthy item is that this engine was run on VP Fuel N20 gasoline, which Pettis says makes 35-40 hp less than VP C14 or Q16. "We were dialing it in for nitrous, so we dyno with the fuel that we run on the track to eliminate a variable," he explained.
All this talk of nitrous oxide might have you wondering about what was plumbed into this manifold. "We installed two Edelbrock E3 direct-port nozzle systems in the runners and then added a third stage of nitrous with our Punisher plenum system," commented Steve Johnson of Induction Solutions, a nitrous specialty company located in Brooksville, Florida. Johnson also flowed all three nitrous systems before shipping the intake back to Pettis Performance. The main purpose of flowing the system is to meter the pounds/hour for both the nitrous and fuel. Induction Solutions also monitors the nitrous pressure, fuel pressure, and solenoid amperage draw to make sure things are operating properly. According to Johnson, it gives them an idea of where the systems are with the nitrous/fuel ratios and gives the team a baseline. Manufacturers give a one-size-fits-all tune-up with jet sizes and fuel pressure. The flow testing establishes an application tune-up for that particular system.
On track, the '71 Nova is a beast as the team eclipsed its best time with a 7.82 at 183 mph this past fall at the Street Car Super Nationals. Houston's career best e.t. was even sweeter due to the fact that it was accomplished with a few baby hits of nitrous. "That was with all three systems but they were small and we have a lot more left in it. As the chassis continues to get sorted with the torque converter dialed-in, we can start adding more nitrous. There isn't a whole lot of nitrous going through that thing yet," said Johnson. He went on to say that if the team can get the Nova more efficient through the 60-foot times, then they could run 7.60s on the 275 drag radials. The big, wild, and nasty 598ci is ready for all challengers.
What is it
Pettis Performance-built 598ci big-block
What it made
1,120 hp on motor with three units to go
On nitrous, this big-block powered our '71 Nova to 7-second e.t.'s at well over 180 mph
Check out chevyhiperformance.com for bonus content on this story, including full dyno details.