Building a big-block that's better in every way than the original Mark IV 427/435 is no small feat. But with the technology and high- performance parts that are currently available, it's not as difficult as you might expect. In this article, we'll show you everything you'll need to make this build as easy as possible.
As the saying goes, "It all starts with a good foundation." And the foundation for the original 427/435 was a four-bolt-main iron block with forged rods, pistons, and crankshaft. You can shop eBay and Craigslist for one of these blocks and then try to locate the correct complementary hardware. Even if you're able to do that, you'll still need to have everything machined, Magnafluxed, balanced, and generally reconditioned from top to bottom. When all is said and done, you'll spend a small fortune.
Laying the Groundwork
The plan we chose for our non-numbers-matching C3 should prove easier and much less expensive. We just went down to Jim Ellis Chevrolet and ordered a brand-new ZZ454 short-block. It's the latest, fully assembled, "Gen VI" version of the original iron big-block, and it comes with the same bulletproof four-bolt mains and a forged rotating assembly. Superior metallurgy and a modern forging process make this new block even stronger than the original, and the updated oil-pan gasket and rear main seal eliminate the usual leaks.
One of the keys to making big power is the ability to breathe. Getting the air and fuel in and out is critical. The original Mark IV 427 needed a solid-lifter cam, an 11:1 compression, and 100-octane leaded premium fuel to pump out the 435 horsepower. This new ZZ454, with the factory-installed aluminum heads, is rated at 440 hp right out of the box. With that as our baseline, we initially decided that 500 horses would be a good target. But, truth be told, that figure just isn't as impressive as it used to be.
In the hopes of obtaining even more power, we contacted Air Flow Research (AFR) to discuss our project. AFR recommended its aluminum 265 oval-port heads, which we ordered fully assembled with titanium retainers and heavy-duty valvesprings. The intake ports and combustion chambers were completely CNC'd, as were the bowls on the exhaust ports. The intake side on these heads flows 356 cfm at 0.600 lift, while the exhaust ports flow 270 cfm. That's comparable to the flow numbers on the latest Corvette's cutting- edge LS3 aluminum heads.
On our big-block, these AFRs will flow like Niagara Falls and deliver a high-velocity charge into the combustion chamber to make great torque throughout the powerband. AFR also milled the heads to increase our compression from the ZZ454's stock 9.7:1 to 10.25:1. Even so, we were assured that this motor would run on 91-octane unleaded pump gas all day long.
Since we were upgrading the heads, we decided to install a hotter camshaft as well. We weren't exactly sure what grind we needed, but we knew we wanted a hydraulic cam so we could avoid the frequent valve adjustments common to the original 427/435. The reduced friction and longer life expectancy of a hydraulic roller cam made it the ideal choice.
In spite of our 500-plus-hp target, this motor would be purely for street use. As such, it would need to develop enough vacuum for our power brake system and headlight actuators, and a reasonable idle would be nice, too. Finally, we want it to make power from 2,000 rpm all the way to 6,000 rpm for good driveability. In short, we wanted it all but weren't sure how to get it. Enter Lamar and Rob Walden.
Lamar and Rob are the father-and-son team at Lamar Walden Automotive (LWA). Lamar is an ex-GM engineer and a well-known authority on Chevrolet big-block engines. Rob has been working full-time in the family business for the last 22 years. The pair just celebrated 40 years at their current location, and their engines have been run in everything from circle track and Pro Stock racing to speed boats and even NASCAR.
Lamar is arguably the most knowledgeable person on the planet when it comes to Chevy's 409 big-block—he designed the new all-aluminum 409 and 509 for Bill Mitchell's World Products—and he holds the record for the most powerful 409 ever built. He's also notched 31 wins in Pro Stock behind the wheel of his own car, powered by a self-built small-block Chevy. When it came to selecting a shop to assemble our engine and dyno the finished product, Lamar and Rob Walden were at the top of the list.
The LWA facility is a feast for the eyes, with old-school carbureted monster motors sitting alongside modern fuel-injected hardware. There are engine components, machining equipment, and boxes of high-performance parts everywhere. The facility is also a complete machine shop with three CNC machines, a SuperFlow bench, and an engine and chassis dyno as well. Suffice it to say that "All baking is done on the premises."
When our conversation turned to selecting a cam, Lamar mentioned that he knew Gordon Holloway at Comp Cams. Turns out Lamar was Comp's very first customer back in the early '70s. On that note, we decided to stop asking questions about lift and duration and just have Lamar and Rob spec the cam directly with Holloway. But before they did that, they flowed the AFR heads on their SF600 flow bench and compared them with the flow numbers provided by AFR. They were spot on.
When everything was taken into consideration, including the rear gear ratio, projected engine speed on the highway, vacuum requirements, and more, Rob ordered a custom-ground 0.600/0.610-inch lift, 230/ 236-degree duration, 112-degree LSA hydraulic roller cam. This cam is designed to make power from 1,800 rpm all the way to 6,000 rpm, and it will be happy just cruising along at 2,200-2,400 rpm on the highway. We also ordered Comp's Ultra Pro Magnum roller rockers, pushrods, timing chain, and gearset. Finally, Lamar and Rob recommended a FAST EZ EFI Management System to maximize the power and efficiency of our big-block. (It's the same system the Waldens use on their own dyno.)
We ordered the FAST EZ EFI Multiport System along with a FAST idle air control valve, water- and air-temperature sensors, map sensor, fuel regulator, and all the necessary connections. Summit Racing shipped us a set of FAST 60-lb/hr fuel injectors, Hedman ceramic-coated 2-inch headers, a Summit-brand high-torque starter, and a complete MSD ready-to-run ignition system to put some fire in the hole.
To Top It All Off
F&B Throttle Bodies is pretty well known in Mopar circles, since the company builds and sells triple-throttle-body, fuel-injected, "6-pak" systems for 440 Challengers and 'Cudas. However, designing and building a 3x2 throttle-body system for a big-block Chevy is a bit more difficult because no one currently manufactures an appropriate aluminum intake. One option is to scour eBay and Craiglist to find an original Tri-power intake, but the asking price is usually prohibitive—between $1,500 and $2,000.
Bruce Bridges, the president of F&B, offered a better idea: Start with an old-school, high-rise, dual-quad aluminum intake and modify it to accept the three throttle bodies. His logic was clear. The original '69 427/435s required a very-low-rise intake in order to fit under the stock Corvette hood. This intake wasn't designed for performance at all, but rather to fit the packaging concerns of the engine compartment. Using F&B's custom billet throttle bodies, which are shorter than the original Holley two-barrel carbs, allowed us to use a taller intake that could produce more power. In theory, our modern fuel injection, combined with a high-rise aluminum manifold, should prove almost twice as good as the original setup.
The aluminum dual-quad intake was cut, welded, and machined to order (they don't call it "custom" for nothing). The three throttle bodies are 48 mm and flow 700 cfm each, so air volume shouldn't be a problem. And F&B designed this intake as a "dry" system, meaning that it's only used to flow air; the fuel injectors are located right at the entry to the cylinders, so the fuel never has to travel through the intake. This design is more efficient and should go a long way toward helping us hit our 500-plus-hp target.
The combination of the AFR heads, the great-flowing intake manifold, and the properly selected cam are the real keys to ensuring that our engine makes big power. Tony Mamo at AFR even jumped in to do some serious porting on the intake, to open up the ports, clean up the runners, and smooth out all the rough surfaces. Through hours and hours of weekend work with a handheld grinder, he perfectly port-matched the intake to the aluminum heads. This extra step will give our old-school manifold a real shot at making 550 horses while still fitting under a stock 427 hood.
Putting the Pieces Together
The lead engine builder at LWA is Jonathan Crosby, and the accompanying photos show the complete assembly process as he degrees the cam, installs the AFR aluminum heads, adds Comp's Ultra Pro Magnum rockers, and, last but not least, our Tri-power fuel-injection intake.
Everything Crosby touches is meticulously cleaned with lacquer thinner and then hit with a blast of high-pressure air. He degrees the cam, checks it, and then degrees it again. Every bolt is treated to a little antiseize lube and torqued to the exact spec, and then double-checked. Everything installed at the factory, like the screw-in studs in the heads, is removed and reinstalled with Rite-Lok thread sealant and torqued as required. He's not one to put his name and the LWA stamp on an engine assembly without checking and double-checking every step of the build. In short, it ain't done until he says it is. And when it's done, as we found out on the dyno, it was better than expected.
In our next installment, we'll show you the complete installation process, highlight the performance upgrades we've chosen, and bring you along as we build a bulletproof IRS differential and a super-duty Gearstar electronic 4L60E automatic transmission. Stay tuned.