Organized Street Legal Drag Racing has a profound way of pushing racers thanks to an ever-tightening rulebook and even tougher competitors. It is through those two groups of people that CHP arrived at its latest engine building adventure-a 598ci engine by Pettis Performance. CHP Editor Henry De Los Santos and his longtime racing partner Artis Houston conceived the project as Artis' '71 Nova was falling a step behind in the tough PSCA Wild Street category. This isn't the first collaboration between the two speed freaks; Henry stuffed a different 598 in the Nova back in '06. From there they had refined the nitrous-gulping big-block and the Nova eventually dipped into the 7s with a 7.90 at 176 mph on a set of 275 drag radials.
The rank's competitiveness motivated Henry to go back to the drawing board- along with Pettis Performance and Artis-to develop a 598ci powerplant using what the team had learned with its previous engine and the 540ci bullet before then. On the Outlaw scene, the turbos and superchargers run unrestricted and pretty much dominate many of the popular classes. However, in organized Street Legal drag racing sanctioning bodies-like the NMCA, WCHRA, and PSCA- the power adders are restricted and the tech officials attempt to keep the playing field level between the nitrous, blower, and turbo combinations.
The Wild Street rules offer various weight breaks for nitrous-enhanced big-block engines. While the rules tend to change; at the time, the California-based racers opted to stay with the 598-cid, where the Nova could run at a minimum of 3,325 pounds. If a smaller displacement (up to 550ci) was utilized, the car could have run the scales at 3,175-pounds. Adding a sheetmetal intake, like on this engine, carried an additional 50-pound penalty, and if you ran anything but conventional heads with plus or minus 3 degree valve angle, they would have to add another 50 pounds. Instead, they decided take advantage of the weight break and stick with a conventional set of heads, namely the Edelbrock Victor 24-degree units. Keep in mind that this sounds great in theory; however, it wasn't until recently that they were able to make use of these weight breaks and go from well over 3,400 pounds to 3,330 with the addition of a one-piece front clip and Lexan windows.
Still, don't let the conventional heads and mild cubes (for today's racing standards anyway) fool ya; this engine is capable of serious power. Without getting too far ahead of ourselves; this engine made over 1,100 hp-without the Induction Solutions (Steve Johnson) three-stage nitrous system turned on. It's a lot of power for the faint of heart but a great starting point in the Wild Street game. Since '06, the class record has jumped down to a 7.66 at 184 mph, which was recorded by Chris Groves in his ProCharger-powered Mustang LX coupe. "We also went with the bigger motor to keep up with the blower and turbo combinations," commented Henry and one look at the event results shows the blower and turbo combos are flat-out flying.
As for engine size, Pettis said "to be honest, Artis showed up with a 4.500-inch stroke KP crankshaft (Kellogg Performance) Henry ordered, so that is what we worked with for this combination. The conventional heads and this intake worked really well in feeding all those cubic inches. We normally don't run conventional heads on something this big but on the dyno this engine went to 8,800 rpm pretty easily and that was a pleasant surprise." He continued to tell us that the next common sizes up for crankshafts are 4.625 and 4.750 inches. Pettis explained that the piston speed increases dramatically with those sizes and it hurts the engine's ability to pull very high rpm-where he likes to run nitrous engines. "The higher we can keep the rpm, the more we stay away from the peak torque area on rpm drop-off at the shift. Peak torque is where cylinder pressure is highest and the chances of detonation are greatest. We make the engine push more rpm and ease the drop-off at the shift. 8,800 rpm might sound like a lot of rpm, but it is nothing when compared to a Pro Stock engine, so even 8,800 can still be easy on parts. This motor has the proper pieces to accomplish that," added Pettis.
Looking at the big-picture, the short-block is based on a Dart Big M iron block during a time when drag racers are desperately trying to shed weight and mostly turn to aluminum blocks. "The iron block definitely seals the walls better but it is harder to repair if you hurt the cylinders," said Pettis. He continued, "the car is in a class where you want more weight up front anyway. If we used an aluminum block, then the chassis would really require an additional 50 to 60 pounds to be hung up front. So in reality, the iron block is the way to go for this combination, especially considering where the Nova is going to race."
Moving to the rotating assembly, a KP crankshaft was employed along with GRP aluminum rods and JE pistons. The compression percolates at just 13.6:1, a number that is lower than other engines we've come across at this level. Pettis rightfully explained the reasons for the compression ratio, "on the nitrous stuff we tend to find that the higher compression makes the tune-up window smaller and too finicky. On several occasions we've reduced compression from 15:1 to 13:1 and it didn't result in slower e.t.'s at the track. Then we were able to get a little more aggressive with the nitrous tune and go even quicker with the lower compression. In naturally aspirated trim on the dyno, the higher compression numbers do reveal more power, but that isn't the case on the track." He continued, "We build the motor as if it is spec'd out for the power on nitrous. The cylinder pressure is going to be high with the nitrous so we dump the compression out of it. The cam and compression are mismatched in N/A trim but it comes together when the nitrous is engaged."
Next month, we'll finish up the big-inch mill and pull the pin on the engine dyno. Then it is off to the track in search of quicker times. Stay tuned!
What We Did
Put together a big-inch doorslammer mill
If you want to have a competitive nitrous car in the drag radial scene, then this build is for you