Pettis Performance 598ci Race Engine - Big, Wild, & Nasty Part One

Pettis Performance Builds CHP 's Wild 598ci Race Engine

Michael Galimi Feb 15, 2010 0 Comment(s)

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!

Quick Notes

What We Did
Put together a big-inch doorslammer mill

Bottom Line
If you want to have a competitive nitrous car in the drag radial scene, then this build is for you

Cost (Approx)
$15,000

Sources

Automotive Racing Products
Ventura , CA 93003
800-826-3045
www.arp-bolts.com
Jesel Valvetrain Innovation
Lakewood, NJ 08701
732-901-1800
http://www.jesel.com
Dart Machinery
Troy, MI 48084
248-362-1188
www.dartheads.com
JE Pistons
Huntington Beach, CA 92649
714-898-9763
www.jepistons.com
Total Seal Inc
Phoenix, AZ 85027
800-874-2753
www.totalseal.com
GRP Connecting Rods
Denver, CO 80216
303-935-7565
http://www.grpconrods.com
KP Crankshaft
Jackson, MI 49202
517-788-9200
http://www.kpcrankshafts.com
Moroso Performance Products
Guilford, CT 06437
203-453-6571
www.moroso.com
Pettis Performance
Hesperia, CA 92345
760-244-4415
http://www.pettisperformance.com

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