447 HP Vortec Small-Block Build - Budget Sledgehammer

Knowing the condition of our engine, we had our starting point, and could decide on the course for our buildup. We could've fully rebuilt the engine, grinding the crank, and boring the block to fit oversize pistons as a matter of course, but the excellent condition of the core opened another possibility-that of an old-school rings/bearings/gaskets engine overhaul, rather than a full all-new buildup. There was no doubt that a simple overhaul would be more in keeping with a budget approach, and even represent what could be achieved by someone with a totally stock engine in very good original condition. The biggest downside to this route would appear to be the factory dished pistons, which could hamper the compression ratio enough to compromise output. We weighed the cost benefits, and decided to keep the bottom end stock, and would target the rest of our component selection around making the most of the freshened factory short-block assembly.

Power Parts

We knew the cylinder head choice would be critical to the our effort's success, and carefully considered the choices available in terms of cost and power potential, as well as how these possibilities would dovetail with the components we already had, and our goals for the finished engine. We selected the cast-iron CH350C Lightning cylinder heads from Enginequest. These heads are essentially Vortec replacements, sharing many features with the excellent OEM Vortec heads, but sufficiently improved in ways that would help achieve more power than the stock Vortecs. The Enginequest heads are aftermarket iron castings, designed with good airflow and power in mind. The intake ports feature 180cc runners, which is sized right on target for a 350-cube engine, for good torque production and port velocity. We liked the compact 62cc chambers, which would help boost the compression ratio with our factory dished pistons. In fact, with moderate milling (25 thousandths), we were able to achieve slightly over 10:1 compression with 58cc chambers, which is right were we'd want to be for serious pump-gas street performance. The intake ports flow in the neighborhood of 230 cfm, which is enough to produce well into the mid 400hp range, based on common measures of power potential versus airflow capacity. The key for us would be to take maximum advantage of the available flow, extracting all the power these heads are capable of. As a point of interest, Shaver Racing Engines performed our flowbench testing and head assembly prior to our engine's assembly at Speed-O-Motive. Shaver offers EQ Vortec heads in assembled form, starting at $860.50 for a pair.

Of course, our avenue for taking advantage of the head's potential lies right in the heart of our engine's short-block; the camshaft. With a hydraulic roller cam, we'd have the potential to safely employ much more lift than we would dare use with a flat-tappet cam on the street, and still keep the overall duration at a moderate level. This would help generate strong torque in the engine's intended operating range of approximately 6,000 rpm. By maximizing the torque production, we're also maximizing the horsepower the engine will deliver in its operating range. We had frequent PHR contributor David Vizard spec our cam, and he selected a custom COMP Cams hydraulic roller single-pattern grind, with 224 degrees duration (at .050) on the intake and exhaust lobes, and 0.352 inch lobe lift. David specified a relatively tight 108-degree lobe separation angle, which would serve to bring the torque on hard, and preserve cylinder pressure compared to a similar cam with a wider spread.