There's a sweet spot in the horsepower-per-dollar equation, and this 355 has its coordinates firmly locked onto that juicy territory. Scoff, if you will, at its mediocre 467hp output, but printing a big number on the dyno sheet with utter disregard for fiscal responsibility isn't what this motor's about.
With the caliber of cylinder heads, stroker rotating assemblies, and valvetrain components on the market today, cracking 550 hp with a small-block is cake. Eclipsing the 600hp mark requires just a smidgen more effort. However, with those incremental gains in power comes an alarmingly disproportional hit to the checkbook. While this 355 was built for less than $4,000, a 550hp Mouse could easily cost twice as much. Sure, speed costs money, but what if you don't have the greenbacks to play with the big boys?
Enter Terry Shallington's low-buck 355. Like most working stiffs, Terry had a real-world budget, which meant that spending $10,000 on a motor was out of the question. The formula for the buildup was quite simple: Buy what you can afford, even if it means leaving some power on the table. The final product is a ridiculously simple 355 mill that utilizes a factory four-bolt block, a stock GM steel crank, Eagle I-beam rods, forged Speed-Pro pistons, World Products iron heads, and a 255/263-at-0.050 Comp solid flat tappet cam. With a price tag right at $4,000, the 355's 467hp output works out at roughly $8 per horse.
Assuming for the sake of argument that a 625hp small-block would ring up a $10,000 tab, the math works out to $16 per horse. In other words, that would be 100 percent more money for just 22 percent more power. Like we said, this 355's objective is finding the sweet spot-and gloriously exploiting it.
From Attic To Dyno
In an interesting backstory to this engine buildup, some of the antique parts came straight out of the attic. Terry is the original owner of an all-original '69 Z/28, and after the factory 302 went poof! decades ago, he went on an extended hiatus from drag racing. Now that the kids are all grown up, he's hitting the local bracket racing scene again and is even considering competing in Stock Eliminator. Before that could happen, he enlisted the help of the School of Automotive Machinists in Houston to build a durable powerplant. Most of the components are new, but to help keep costs down, Terry dug up some 30-year-old parts from his street racing days. Not only are the battle-proven Crane roller rockers, Victor Jr. intake, stock Z/28 carb, and Stahl headers interesting pieces of nostalgia, but they still perform exceptionally well by today's standards.
Quick Notes
The Build
A stupid-easy pump-gas 355 bracket motor
Bottom Line
Nothing fancy here, just an $8-per-horse formula
A large cost-savings comes...
A large cost-savings comes from our swapmeet finds: a four-bolt block and a factory steel crank. After cutting the journals 0.020/0.020 and align-honing the block, the crank was ready to drop in. A benefit of a stock-stroke crank is the reduced labor costs when balancing the rotating assembly, which required simply removing a wee bit of material from the front counterweight. Since the motor won't see much past 7,000 rpm, main studs are not necessary.
The 5140 Eagle steel rods...
The 5140 Eagle steel rods measure 5.700 inches and 565 grams. Eagle's H-beams would have been preferable in a heavier-duty application, but they would add mass and dollars. Furthermore, the I-beams are plenty stout considering the 355's relatively moderate rpm range and power output.
At only a few bucks over a...
At only a few bucks over a set of hypereutectic pistons, these Speed-Pro forgings are a raging bargain. They feature ribbed skirts for improved oil retention and a Duroshield coating for reduced friction. A testament to the overall simplicity of the motor, the ring grooves accommodate an OE-like 5/64-, 5/64-, 3/16-inch ring pack. Although it comes with a weight penalty, using short rods also comes with the benefit of the piston's thick, 1.56-inch compression height, should they ever encounter nitrous.
To ensure pump-gas compatibility...
To ensure pump-gas compatibility with the motor's 10.5:1 compression, quench was optimized with a 0.040-inch-thick head gasket and by zero-decking the block.
The cam's 255 degrees of duration...
The cam's 255 degrees of duration combined with a large, 2.08-inch intake valve resulted in minor piston-to-valve contact, which required slightly enlarging the intake valve reliefs.
GM engineers missed the mark...
GM engineers missed the mark in the '60s but were on the right track. The factory Z/28 oil pan featured a windage tray,...