Pontiac GTO 400 Engine Block Build Up - Poncho Honcho

Given the current engine technology in the Pontiac hobby, building a big-cube Pure Pontiac engine from a 400 block is easier than ever thanks to the many stroker combo choices for 3.00-inch main engines. When Orwin Middleton of Santa Barbara, California, decided he wanted more power for the street to motivate his rare '61 Royal Pontiac Catalina, he pulled the transplanted '67 400 that sat in its engine bay and paid a visit to Joe Sherman Racing Engines in Santa Ana on the recommendation of storied racer and noted Santa Barbara engine builder, Bob Joehnck.

Coincidentally, Sherman was already in the process of building a Pontiac 455 with an Edelbrock top end featuring its aluminum heads, Performer RPM intake, 800-cfm AFB carburetor, a set of headers, and a street performance roller camshaft from Comp Cams. Sherman is known industry wide for incredibly strong street engines as well as top race engines. He even won the inaugural Popular Hot Rodding Magazine Engine Masters Challenge in 2002!

Middleton told him about his '61's proposed combo-a big-inch torquey, yet streetable, engine backed by a 2,500- to 2,800-rpm stall converter, a Turbo 400 and a 3.42 Safe-T-Track rear. With these specs in mind, Sherman devised a plan to have the block machined and bored 0.060 over to 4.181, and to use a 4.210-inch stroke, 3.00-inch main cast crank, stock length rods, 0.030-over 455 KB hypereutectic pistons and a Comp Cams hydraulic roller cam. The top end recipe would duplicate his other customer's 455 with Edelbrock parts.

Joe Sherman Racing Engine's...        read full caption Joe Sherman Racing Engine's cast crank features the 4.210-inch stroke of a 455 and the 3.00-inch mains to fit the 400 block. Installing a 455 spec crank in a 3.00-inch main block sometimes requires mild clearancing at the front of the block where the front counterweight will travel.

For the record, every block...        read full caption For the record, every block spec and dimension was checked out, noted, and blueprinted for the '67 WT-code block. To accept 0.030 455 pistons, the cylinders were bored 0.060-inch.

Stock 6.625-inch connecting...        read full caption Stock 6.625-inch connecting rods were press-fit onto Keith Black (KB) hypereutectic pistons. This type has the increased strength of a forged piston with the lesser expansion rate of a cast one. Less piston-to-cylinder wall clearance means better ring seal.

Sherman explained to Middleton that this 462 cubic inch combination would produce 500-plus horsepower at a livable 5,000 to 5,200 rpm with almost 600 lb-ft of torque. Though we typically see forged rods and pistons in these types of builds, Sherman also said that the hypereutectic pistons and cast rods would be cost-effective as compared to forged pieces, and durable in this application because peak power is made at just 5,200 rpm. Middleton was floored! To his old-world brain, these power figures bordered on Amtrak diesel territory! Sherman suddenly found himself with Middleton's Pontiac engine to build as well. Let's see how it all turned out.

Dyno Results
The engine was dynoed on Joe Sherman Racing Engine's SuperFlow 901 engine dyno. For this pull, the fuel was 91-octane, the timing was set to 39 degrees and the jets were the same as listed in the engine buildup worksheet.

Joe related, "though the carb spacer normally does lean the mixture slightly, the out-of-the-box jetting was nearly perfect for this combo."

Here's the short-block buttoned...        read full caption Here's the short-block buttoned up just prior to fitting the oil pump. By retaining the two-bolt mains and stock caps and employing a cast 4.210-stroke crank, cast rods, and hyper-eutectic pistons, the budget is kept in check, while power for the street is generated. For added bottom-end insurance or higher-rpm potential, forged connecting rods can be used for your buildup.

Money was well spent on the...        read full caption Money was well spent on the benefits of a hydraulic roller camshaft from Comp Cams. The design of the roller cam lobes lets the valves reach maximum lift more quickly per degree of duration than flat-tappet cam lobes, which aid cylinder filling and evacuation, thus increasing power output. Less overlap required in a hydraulic roller as compared to a hydraulic flat-tappet to get this increased power can result in a smoother idle and improved low-speed performance. There's also a reduction in friction thanks to the roller lifters.

Roller cams generally don't...        read full caption Roller cams generally don't need any initial start-up lube, but Joe Sherman lubes the lobes and lifters anyway.