Keeping it Simple
One universal tenant of any successful engine build is capitalizing upon the strengths of your engine platform of choice, and playing down its weaknesses. In the case of a 455 Olds, that entails keeping the operating range reasonable, and maximizing low and midrange performance rather than having delusions of high-rpm glory. Moreover, not-so-common engine platforms like the 455 can run up a big bill, as aftermarket parts are far less plentiful than with a Ford or a Chevy. Consequently, the goal with our 461 was to keep the build as simple as possible while shooting for 500 hp and 525 lb-ft, and limiting engine speed to 6,000 rpm. As it turns out, we exceeded our power and torque targets ever so slightly while capping the total for parts and labor at $8,500.

Given our power and torque objectives, there wasn't much need to expand displacement much beyond 455 ci. Starting with a stock 455 short-block pulled out of a '71 442, we discarded the factory rods and pistons and increased the bore 0.030 over to 4.155 inches. Although some Olds blocks can be bored 0.120 over, doing so can compromise cylinder wall strength and requires custom pistons in most instances. On the other hand, 455 blocks have sufficient wall thickness for up to a .060 overbore without the need for sonic checking, and off-the-shelf pistons are readily available in 4.155- and 4.185-inch diameters. We opted for a set of SRP 10.44:1 forged pistons, and matched them up to stock-length Eagle 6.735-inch steel rods.

So far so good, but the selection of aftermarket Oldsmobile crankshafts is miserably limited. While aftermarket forgings are available, most are only offered with the stock 4.250-inch stroke. Fortunately, with big 3.000-inch main and 2.500-inch rod journals, factory 455 cranks are plenty stout. A very small number of 455s were blessed with forged cranks from the factory, but they're nearly impossible to find these days. Most came equipped with cast- or nodular-iron crankshafts, which, thanks to their generous journal overlap, can easily handle up to 650 hp. Considering the durability of the stock nodular crank in our 455 core motor, it made no sense to shell out big dollars for an aftermarket forging. Instead, we simply turned the journals .010/.010 and called it a day.

If you're building a heavy-breathing Olds that has enough cylinder head airflow to take advantage of some extra cubes, it is possible to offset grind a factory 4.250-inch crank to 4.500 inches. This simply involves grinding down the Olds' big 2.500-inch crank pins to 2.200 inches, and hooking them up to big-block Chevy connecting rods. If that's too much of a hassle, Eagle has just released a 4.500-inch cast steel crank with big-block Chevy crank pins that lists for under $600. Combined with a 4.155-inch bore, a 4.500-inch crank would yield a total of 488 ci. Although an extra 27 ci over our 461 is certainly enticing, the custom pistons and the extra machine work it would require make it a very expensive proposition.