The team at Hot Rod partnered with JE Pistons and Dart Machinery in 2020 to build the biggest big-block Chevy possible using off-the-shelf parts. This effort results in the creation of a 632ci using production-based parts that you can source from almost anywhere.
You can find crankshafts online with up to a 5.50-inch stroke, but the requirement of a 5-inch bore spacing engine block means you don’t have an off-the-shelf product.
Bigger-than-stock bore spacing engine blocks and billet blocks are available if you want to go even larger.
Parts Used to Build the 632 Big-Block Chevy
The team used the following components to build their 632ci big-block Chevy.
- A tall deck big Chevy engine block
- A 4.75-inch stroke crankshaft
- Machining equipment
When the team received the Dart Big M Mark IV block, it came with an unfinished bore size of 4.6 inches. The group partnered with Nelson Racing Engines to perform the necessary machining to bring the part to specs, including a final honing of the cylinders.
The deck height of an engine is the distance between the primary centerline of the crankshaft and the top of each cylinder bank. The standard big-block design for Chevys is 9.8 inches. The team went even bigger with an additional 0.4 inches of height to accommodate the long-stroke crank with their intended design.
As part of the creating process, the team had Nelson Racing Engines zero-deck the block.
How Were the Cylinders Filled?
The Hot Rod team filled the big cylinders of the 632ci big-block Chevy with 6.7-inch H-beam connecting rods and forged JE pistons.
The pistons had a flat-top design equipped with a 4cc valve relief. The long connecting rods put the wrist pin through the oil control ring groove.
That step necessitated a support rail for the oil rings to create a usable outcome.
You can follow the entire sequence of events, including photographs of the work, at this link from Hot Rod.
Challenges Encountered During the Creation Process
The team took the time to verify clearances, compression, and measurements multiple times while creating the 632 big-block Chevy.
When one piston was installed successfully, the group verified the volume of the bore. Since the block was zero-decked and the pistons weren’t domed or dished, this measurement confirmed the 4cc valve relief was accurate. Then the team used a 4.6-inch ring compressor to install the rods and remaining pistons.
Areas near the oil pan flange with the 632ci required clearance to accommodate the long stroke. Some material had to be removed at the base of the cylinder walls for the same purpose, along with the rotating assembly and the counterweights of the crankshaft.
Once all of the pistons were in place with the fastened torqued correctly, the assembly of the big-block Chevy was complete. That meant the final product at the following specs.
- A 4.6-inch bore.
- A 4.75-inch stroke.
- Deck height of 10.2 inches for the engine block.
- Compression ratio of 10.6 to 1.