Jason’s Biscayne wagon weighs...
Jason’s Biscayne wagon weighs approximately 4,500 pounds—about twice as much as the Pro Stocker he drives in the NHRA Full Throttle Drag Racing Series—so he needed some big cubes. Here’s the GMPP Gen VI 502 block he used as the foundation for the Biscayne’s engine. It was bored to 4.500 inches, align-honed, and jet-washed before the build.
It all started innocently enough. Following a race last year, Summit Racing Equipment NHRA Pro Stock driver Jason Line bought a ’68 Biscayne station wagon as a side project and laid out a quick, simple plan: Take an old 427 engine from a donor car, refresh it, and drop it harmlessly between the framerails of the wagonthen came Plan B.
Almost from the start, the guys at the shop were hacking on me about putting a relatively stock engine into the wagon, says Jason, who also builds and tunes the engines for the Summit Racingsponsored KB Racing Pro Stock team. That started me thinking. One thing led to another, and before I knew it, I was starting to assemble the pieces for a completely new custom motor.
Jason’s Plan B was to build an all-new mild 9.6:1 compression 557ci mill with the goal of topping 750 hp on pump swill. A lot of people build 540s, 565s, or 572s, but I wanted something a little different, Jason says. Basically, I wanted a race engine with low compression so I could drive it on the street.
Jason started with a GM Performance Parts Gen VI 502 block with four-bolt mains to handle the considerable power he had planned. He had it bored out to 4.500 inches and clearanced for a 4.375-inch stroke crankshaft, producing 557 ci. He then contacted Summit Racing to help piece together the remainder of the components for the build.
The rotating assembly includes an Eagle Specialties forged crank with H-beam connecting rods and Diamond coated pistons. The top end is anchored by a set of Trick Flow PowerPort 360 cylinder heads, which got a little special attention from Jason; using his NASCAR and NHRA engine building experience, he altered the intake runners to increase airflow from 365 to over 400 cfm. A port-matched Trick Flow single-plane intake and a Willy’s carburetor complete the top end.
The valvetrain centers around a COMP Cams solid roller camshaft, which Jason says is mild and durable enough for the street without sacrificing the power numbers he was shooting for. In fact, the 557 exceeded Jason’s goals, delivering 812 hp on the dyno.
Anyone can duplicate this build using parts right out of the Summit Racing catalog, bolt it all together without the extra port work, and get close to the horsepower we made, Jason says. That would certainly be enough for most people, but our team motto is: Anything that can be done can be overdone. Jason’s 557 is proof of that.
The main bearings were prefitted...
The main bearings were prefitted with clearances between 0.0025 and 0.0030 inch; the typical range the team shoots for with its Pro Stock engines. Jason chose an Eagle Specialties forged crankshaft to handle the 812 hp at 7,000-plus rpm.
Gen VI blocks are designed...
Gen VI blocks are designed to work with one-piece rear main seals, but the Eagle Specialties crankshaft required a two-piece rear main seal. To make the block and crank work together, Jason used a special B&B adapter to give the rear main seal a place to sit. End clearance was set at 0.005 inch before the main caps were torqued to 105 ft-lb.
Jason chose Diamond pistons,...
Jason chose Diamond pistons, which are used on the team’s Pro Stock engines. The team has its competition pistons vertically gas ported, but for this street-oriented 557, Jason went with a lateral gas porting option. The gas porting allows cylinder pressure to get behind the top ring and push the ring against the cylinder wall for better sealing.
For the piston ring package,...
For the piston ring package, Jason went with Total Seal. An oil ring spacer was installed because the compression height of the piston caused the wristpin bore to break into the ring lands. Using fish scale, he set the oil ring tension to 11 pounds of drag to prevent the big-block from oiling or smoking.
The pistons were installed...
The pistons were installed on a set of Eagle Specialties 6.385-inch length H-beam connecting rods. Diamond recommends a 0.0065-inch piston-to-wall clearance, but Jason elected to go with a tighter 0.0060-inch clearance to keep the engine running quieter.
At the heart of the engine...
At the heart of the engine is a custom-ground COMP camshaft with 254/270 degrees of duration at 0.050-inch lift that was installed and set into place with a Jesel front cover. The custom ground, solid roller cam and lifters were used to avoid the high rpm “valve float” sometimes associated with hydraulic valvetrain setups. Cam endplay was set to 0.005 inch using a set of shims, which was supplied with the cam seal.