No doubt about it, building a big-block Chevy is a more expensive proposition than one of its small-block kin; however, many favor these engines because their easy power and bountiful cubes deliver dependable torque. In production form, the 454 is by far the most common member of the big-block family-an engine that earned a legendary reputation at the pinnacle of the factory muscle era. It has continued in more recent years as a sturdy workhorse in trucks, but back when musclecars ruled the streets, the LS6 454 was Chevy's top dog, with 450 gross horsepower from the factory. These days, most builds will be based upon the readily available late-model truck engine.
Build It
Starting at the foundation, any 454 engine block can serve as an excellent basis for a stout performance build. Later Mark V engine blocks actually featured improvements like a one-piece rear crankshaft seal, provisions for hydraulic roller cams, and a camshaft thrust plate, though some also did away with the machined pad for a mechanical fuel pump. Internally, some earlier engines came with a forged crankshaft and high compression pistons; however, don't feel the need to hunt down the rare factory performance stuff. The factory iron crank has proven to be remarkably reliable, and the pistons will be replaced in the course of a rebuild anyway. Our engine build is based on a common Mark IV engine core, and the plan for the bottom end is simple-a basic rebuild of the original equipment, as with any stock rebuild. Our only concession to the performance objectives of the engine would be to substitute higher compression pistons and a good set of rings.
We selected a set of KB hypereutectic pistons (UEM-KB207060-8), which feature a 0.250-inch hollow dome for a net volume of +25.5 cc. These pistons retail for a little more than standard replacement pistons, but the added compression ratio they provide is a welcome addition. These pistons are cut for 1/16-inch compression rings, which reduces friction compared to the 5/64-inch stockers. We didn't skimp when it came time to fill the grooves, selecting a quality Total Seal moly ring set. Moly rings are worthwhile in any build, offering reduced friction and improved sealing and bore life.
Other than the moderately upgraded pistons and rings, the rest of the bottom end received nothing but a standard rebuild. The block was cleaned, inspected, and machined by Speed-O-Motive, including boring and honing to size, and decking to zero deck with our choice of KB pistons. Since our production iron crank was in terrific condition and checked out fine, it was simply given a polish and balanced for the new pistons. The factory rods were resized and retained the stock bolts, and the KB pistons were installed as a press-fit on the rods.
Power Parts
There was definitely nothing exotic about the basic bottom end of the engine-just your everyday 454 with a bump in piston spec. These KB pistons would be enough to provide a compression ratio of more than 10:1, but that alone wouldn't add much greater power than a plain old truck 454. To step things up, power parts needed to be included in the mix, and first on that list was the camshaft. Later 454 engines came from the factory with hydraulic roller cams, but to take things to the next level, we went with a solid roller. A solid cam provides much improved high-rpm stability, particularly with the OEM big-block's heavy valvetrain. No, we weren't after a wild drag race roller, but a moderate street roller, and we looked no further than COMP Cams for one of their Xtreme Energy Street Roller grinds.
With a single-pattern stick cut on COMP's No. 4874 lobes, lobe separation came in at 108 degrees. The tight center and fast roller cam action helped torque come up hard and fast. With 242 degrees of duration at .050-inch lift, the cam timing is not excessive, striking a good balance between power and driveability. In combination with the big Chevy's 1.7:1 rocker ratio, the valve lift is substantial, translating to .647-inch gross lift at the valves.
So our 454 project was turning into a stocker with higher compression pistons and a fairly substantial cam. While those factors would aid in our power plans, it was going to take more than that to breathe some life into those inches. Cylinder heads are also key players. The original high-performance big-blocks came with monstrous rectangular port heads, but unfortunately, you won't find a set of those on a later truck engine core. In fact, chances are you won't find a good oval-port set either, since many of these engines were produced with the dreaded "peanut-port" heads. Don't expect to flow much power through that tortured iron.
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It may not look exotic, but our basic 454 truck short-block core from AA Midwest ($600) provided most of the hard parts we intended to reuse in the bottom end. The stock rods and cast crank should prove plenty durable in a street application, as will the production four-bolt main Mark IV block. |
While not as exotic as an LS6 musclecar plant, it doesn't take much to build one of these into a beast. Machine work to the block (by Speed-O-Motive) consists of the bare bones-a bore, hone, and deck. |
Speed-O-Motive resized the stock rods, fitted new bolts, and hung a set of KB Hypereutectic cast pistons. The KB pistons feature a 25.5cc net dome volume, bumping the compression ratio to 10.28:1. |
Nothing fits like stock parts. The original cast crank was right at home in the crankcase, feeling the love of a fresh set of Clevite bearings. No special prep required here. |
While a lot of the hardware going into the short-block is stock, there is nothing remotely stock about the COMP solid roller stabbed inside. With 242 degrees of duration at 0.050-inch lift and 0.647-inch lift, this single-pattern street roller adheres to the short-duration/high-lift school of thought, providing high torque production and good idle quality for its power level. |
The piston and rod assemblies were loaded for installation with a file-fit set of Total Seal moly rings and Clevite rod bearings. Plain oil is all it takes for assembly lube. |
A tapered-bore ring compressor is ideal for guiding the pistons into the fresh bores. Once each piston is lightly tapped into the bores, the rods are torqued to specs and the crank is turned to check for smooth rotation. |
It takes a considerable amount of volume to obtain a high-performance compression ratio from a 454 with most cylinder heads. With a piston rotated to TDC, the sizable domes look impressive. Note the flat of the piston is dead flush with the deck, providing appropriate quench clearance to the head, once installed with a .040-inch gasket. |
A look from the pan side of the assembled short-block shows little to give away the goal of a serious street piece. Most of the hardware is factory pig iron, and even the OEM main fasteners are reused. |