455 Buildup

Back in the good old days when there was no replacement for raw displacementand what was good for General Motors was good for America, the General produced no less than three distinct 455ci engines: a Buick, an Olds, and a Pontiac. All were unique designs, sharing only a common rear block-face bolt pattern. In their day, the General's 455s were stump-pulling torque monsters, designed to effortlessly pull luxo heavy metal in style and comfort. But is any one 455 clearly superior to its sisters? To find out, Car Craft, in conjunction with Westech Performance, has decided to build up an example of each 455 using commonly available off-the-shelf performance parts. Subject to real-world parts availability, we'll build each motor as identically as possible using modern high-flow aluminum heads, about a 10.0:1 compression ratio, an aggressive (yet still streetable) Comp Xtreme Energy XE274H hydraulic flat-tappet cam, Hooker Super Competition headers, a dual-plane intake manifold, and a Speed Demon 750-cfm double-pumper carb. Although the engines will use a good cam and heads, we'll assemble the bottom ends just like an average car crafter would: no exotic parts or niche tricks--just good machining practice, premium Federal-Mogul bearings, Speed-Pro piston rings and forged pistons, and Fel-Pro gaskets. This month we'll showcase the buildup and test of a '72 455 Olds. In coming months, we'll pound a Pontiac and bang on a Buick. Which one will end up the top dog? Your guess is as good as ours. Stay tuned.

Bottom End
Westech turned the engine over to Dougan's Engine Rebuilding for inspection, hot-tanking, and machine work. The block was surfaced to square-up the decks, then align-honed to true up the main-bearing bores for the stock crank, which was cross-drilled for improved oiling and ground 0.010-inch undersize on both the main and rod journals. The junkyard block had already been rebuilt once before, so it was bored 0.060-over, then final-honed with a torque plate. After the stock Olds rods passed magnetic-particle inspection, they were reconditioned, fitted with new ARP bolts, and pin-fit to the pistons. Next, it was back to Westech where the balanced rotating assembly was assembled with Federal-Mogul H-14 competition-series main and rod bearings, which have a unique lining bonded to an extra-high-strength steel backing. The rings are a standard-gap premium Speed-Pro set (5/64-inch high-strength plasma-moly ductile-iron top; 5/64-inch cast-iron second; and 3/16-inch standard-tension SS-50 oil control). Unlike standard rebuilder rings that often come gapped way too wide, the Speed-Pro set was factory-gapped to the recommended minimums.

Cam and Valvetrain
Westech stuffed the latest Comp Cams hydraulic flat-tappet street cam in the Olds: an Xtreme Energy grind with an aggressive lobe design that produces better throttle response and top-end power than other cams with equivalent 0.050-inch tappet-lift durations, even while maintaining increased engine vacuum. For better valvetrain stability, the Edelbrock heads replace the stock Olds nonadjustable pedestal-mount setup with 7/16-inch screw-in studs and guideplates set up for 3/8-inch-od hardened pushrods. This requires custom-length pushrods and non-Olds rocker arms. With Edelbrock's stock-height valve covers, it was necessary to double-stack valve-cover gaskets to provide clearance for the Comp Cams aluminum roller rockers.

Cylinder Heads
Engine technology has come a long way since the '60s. The biggest advances have been in cylinder-head and camshaft design. That's where the power is, and if you're on a budget, that's where you should spend your hard-earned bucks. We went with Edelbrock's Performer RPM Olds heads, which come complete and ready to run with stainless steel 2.072-inch intake/1.680-inch exhaust valves, hardened ductile-iron valve seats, phosphor-bronze guides, valvesprings, guideplates, and rocker-arm studs. Out of the box, they flow about as well as today's modern aluminum 23-degree small-block Chevy heads--which is quite an improvement over production Olds castings.

Induction, Ignition, Exhaust
The Olds was equipped with an Edelbrock Performer dual-plane intake fed by a Speed Demon 750-cfm carb, ignited by an MSD billet Olds distributor, and exhausted by Hooker Super Comp headers. Note that the port openings on most street-header flanges are actually smaller than the port exit dimensions of many big-block Olds heads. Hooker 17/8- and 2-inch primary-tube header sets are exceptions.

Test Results
Based on prior experience with big-block Olds engines, we expected a torque monster, and we weren't disappointed. With 38 degrees of total lead and No. 80/86 jetting in the Demon carb, the engine put out so much torque at so low an rpm it exceeded the capabilities of Westech's SuperFlow dyno. Westech recorded a peak of 565.3 lb-ft at 3,500 rpm, but that was already on the downside of the slope. We may, in fact, be looking at a 600-lb-ft engine! The engine made more than 500 lb-ft from 3,500 through 4,800 rpm and more than 400 hp from 3,800 through 5,500 rpm, the highest rpm point obtained in the test. A peak 469.6 hp was recorded at 5,200 and 5,300 rpm. While these numbers make for a tire-melting street engine, Westech feels an intake optimized for higher-rpm performance--such as a Performer RPM or even a Victor Jr.--is needed to fully unleash the potential of Edelbrock's Olds heads. An Olds 455 makes so much low-end torque it's almost impossible to hurt the bottom end. Edelbrock, are you listening?