The 602 and 604 crate motors are two of the most popular models of GM Performance Parts crate motors. These engines are designed for race cars, hot rods, and street performance vehicles. They are both considered “small block” V8 engines, and they share many similarities, but there are some key differences that make them suitable for different applications. In this article, we will take a look at what those differences are and why they matter.
Table of Contents
Comparing the Engine Blocks
The 602 and 604 crate motors both use a cast iron block, but the 602 has a longer deck height than the 604. The 602 also has a taller deck height than the production LS1, LS2, and LS3 blocks. The 602 has a 10.2-inch deck height, while the 604 has a 9.8-inch deck height. The shorter deck height of the 604 makes it easier to fit into tighter engine bays, while the 602 may require minor modifications to fit.
Comparing the Cylinder Heads
The 602 crate motor uses a cast iron cylinder head with a single-valve design. It has a combustion chamber volume of 64cc and a compression ratio of 9.5:1. The 604 crate motor uses aluminum cylinder heads with a two-valve design. It has a larger combustion chamber volume of 66cc and a higher compression ratio of 10.7:1. The higher compression ratio of the 604 makes it more suitable for high-performance applications.
Comparing the Crankshafts
The 602 crate motor uses a cast iron crankshaft with a 3.48-inch stroke, while the 604 uses a nodular iron crankshaft with a 3.6-inch stroke. The longer stroke of the 604 gives it a higher torque output, which is beneficial for high-performance applications.
Comparing the Pistons
The 602 crate motor uses cast aluminum pistons, while the 604 uses forged aluminum pistons. The forged pistons are stronger and more durable, making them more suitable for high-performance applications.
Comparing the Camshafts
The 602 crate motor uses a hydraulic roller camshaft, while the 604 uses a solid roller camshaft. The solid roller camshaft is more aggressive and allows for higher engine speeds, making it more suitable for high-performance applications.
Comparing the Valves
The 602 crate motor uses an intake valve diameter of 2.02 inches and an exhaust valve diameter of 1.60 inches. The 604 uses an intake valve diameter of 2.02 inches and an exhaust valve diameter of 1.55 inches. The smaller exhaust valve of the 604 allows for more airflow and increased power output.
Conclusion
The 602 and 604 crate motors are both excellent options for race cars, hot rods, and street performance vehicles. They both share many similarities, but there are some key differences that make them suitable for different applications. The 602 has a longer deck height and a cast iron cylinder head, while the 604 has a shorter deck height and aluminum cylinder heads. The 604 also has a larger combustion chamber, a higher compression ratio, a longer stroke, forged pistons, a solid roller camshaft, and a smaller exhaust valve.
