This Aluminum V8 BEAT Carroll Shelby's Cobra By 11 SECONDS!

What if the most powerful small-block Chevy V8 ever built in the early 60s was one that the company itself tried to have destroyed? Not discontinued. Not shelved. Destroyed. We're talking about an all-aluminum racing V8 that weighed about 85 pounds as a bare block, made somewhere between 485 and 550 horsepower depending on which source you trust, and was so secret that every bolt on it was safety-wired like an aircraft engine so that if anybody opened it up and tampered with it, Chevrolet would know. They only finished 12 of them. They lettered each block A through L. And when the brass on the 14th floor at GM found out what their own engineers had been doing, the order came down to shut it all down and get rid of everything. But before that happened, three of these engines showed up inside Corvettes at Nassau Speed Week and beat Carroll Shelby's Cobras by 11 seconds a lap. This is the story of the all-aluminum 377 small block. And it's one of those engines that almost nobody talks about because it was never supposed to exist in the first place. Now, to understand why Chevrolet would secretly build a race engine inside a company that had banned itself from racing, you need to know what was going on. In 1957, the Automobile Manufacturers Association put pressure on all the major American car companies to pull out of factory-sponsored motorsports. Everybody signed off on it. And GM actually followed through. Officially, Chevrolet was out of racing. But Carroll Shelby didn't care what GM had agreed to. By the early 60s, his AC Cobra, this tiny British roadster with a Ford V8 stuffed in it, was making the Corvette look slow at pretty much every road course in the country. And Zora Arkis-Duntov, who was Chevy's chief performance engineer, and honestly the reason that the Corvette became anything more than a six-cylinder boulevard cruiser, Duntov watched the Cobras win race after race, and it ate at him. See, Duntov knew the production 63 Stingray was a gorgeous car. But at about 3,000 pounds, it was built to also be somebody's daily driver. And on a racetrack against something as light as a Cobra, it just couldn't keep up. So he wanted something stripped down and purpose-built, closer to 2,000 pounds, with nothing on it that didn't make it go faster. That car became the Grand Sport. But a 2,000-pound race car with a regular cast-iron small block still wasn't enough. If the car was going to be light, the engine had to be light too. Now, here's something that almost everybody gets wrong about this engine. Duntov gets all the credit for the aluminum small block. He didn't start it. Ed Cole did. Cole was Chevrolet's chief engineer from 52 to 56, and the guy who actually designed the original small block Chevy V8, which is probably the most important American performance engine ever made. Cole figured if you cast the block in a new aluminum-silicon alloy, got rid of the valve seat inserts, the valve guide inserts, and the cylinder liners, you'd cut the weight almost in half while also cutting costs. On paper, it made a lot of sense. In practice, it was a disaster. Sandcast aluminum is porous, and every time they machined a block, cavities would open up in the casting walls. They were throwing out more than they were finishing, and the whole point was to save money. And then Duntov put one of the early aluminum engines into his C-E-R-V-1 car, took it out in 1959 when it got cold, and the intake valves froze solid to the guides. Just stuck. So a lot of people inside Chevrolet figured the aluminum concept was dead before it really got going. But the version of the 377 that went into the Grand Sports was a much more refined piece. They originally planned a 402 cubic inch motor with a 4-inch stroke, but it kept breaking things at high RPM, so they shortened it to 3.75 inches. 377 cubic inches on a 4-inch bore. They had to notch the insides of the block for rod clearance, but the shorter stroke let the engine rev harder without shaking itself apart. Now, the bottom end on this engine was built to a level that production small block guys wouldn't see for years. Thicker main bearing webs, four-bolt main caps standard from the factory, and if you've priced a set of those from the aftermarket, you know they aren't cheap. On the 377, it was just part of the package. It also had dry sump lubrication, which is a bigger deal than it sounds. In a regular wet sump, you throw the car into a hard corner at Nassau. All the oil rushes to one side of the pan, the pickup sucks air, and now you've got no oil pressure at 7,000 RPM. Dry sump means the oil lives in a separate tank, and a scavenge pump feeds it back continuously, so the bearings always have oil no matter what angle the car is at. Up top, four 58mm Weber DC03 side-draft carburetors sat on a cross-ram intake manifold that Winters built for this engine. I came across a guy on the Corvette forums who described an original Grand Sport cross-ram as rare as hen's dentures, which I was not expecting to find in my research, but here we are. The velocity stacks were 23 inches long, tuned for max torque, and there was nothing about this setup that had any business on a street car. Power was somewhere between 485 and 555 horsepower, depending on who you ask. From what I've pieced together, 485 to 550 is the honest range, because there's no surviving factory dyno sheet. Now, there was an even crazier version that existed only on paper. Duntov's dream motor. Hemi-combustion chambers, two spark plugs per cylinder, 2.20 inch intake valves, 1.72 exhaust. Rochester constant flow fuel injection, replacing the Webers. It was designed for his lightweight prototype, but the 14th floor killed it before it ever ran on a dyno. And honestly, on paper, that thing would have been an absolute monster. 12 blocks total, lettered A through L. That's the whole run. Every bolt safety-wired with aircraft procedures. And according to the Corvette report, that safety wire was most likely there to catch tampering because if someone opened an engine and swapped parts, Chevrolet wanted evidence. Now, in early December of 1963, three Grand Sports fitted with the aluminum 377 and those 58 millimeter Webers showed up at Nassau Speed Week under John Mecham's team. The driver lineup was kind of ridiculous. Roger Penske, Jim Hall, Dick Thompson, Augie Pabst, John Cannon, and these Grand Sports absolutely dog-walked the Cobras. 11 seconds a lap faster. Carroll Shelby's own words afterwards were simply, we were outgunned. And I love this detail because a whole bunch of Chevrolet engineers just happened to be on vacation in Nassau that same week. Just a total coincidence, I'm sure. But here's the problem with aluminum. The 377 was a monster in short races like Nassau. But in longer endurance events, it ate itself alive. Aluminum pistons running directly on aluminum bores couldn't stay lubricated over hundreds of miles, and the bores would scuff badly. When Penske ran Grand Sport 005 at Sebring in March of 64, he switched to a steel-block 377 instead. And it ran great. If the guy who just dominated Nassau switches to steel for Sebring, that tells you everything about where the aluminum's limits were. And then Duntov accidentally torpedoed his own program, which always gets me. On December 16, 1963, just days after Nassau, he sent an internal memo bragging about beating the Cobras. And in that same memo, he mentioned that Ford had known the Grand Sports were coming for over a month. So imagine you're a GM executive on the 14th floor reading this. The racing program you shut down months ago is not only still alive, it just won at Nassau. And Ford knew before you did. That memo ended everything. The cars got handed to privateers. Chevrolet backed out of racing. Again. But the engines didn't just disappear. Jim Hall ended up with a few of them for his Chaparral race cars down in Texas, and Chevrolet's deal was very specific. Install the engines, don't touch anything except timing and Weber jetting, race them, and then ship them back for evaluation. So Hall was essentially running a field test program for GM, while GM was publicly saying they had nothing to do with racing, which is kind of a perfect arrangement when you think about it. And then there's Mickey Thompson. Thompson took some aluminum small block castings, pressed in steel cylinder sleeves to drop the displacement to the 255 cubic inch Indy limit, and used them for his Indianapolis 500 program. According to Danny Thompson, Mickey's son, GM loaned his father the original foundry patterns and molds from the 377 program so he could cast about 20 additional blocks. So, for his 1967 Indy effort, I haven't been able to fully confirm that one, but it's consistent with what a lot of long-time Corvette guys have said for years, so I'm inclined to take it at face value. Today, one of the original aluminum 377 engines is on display at the Revs Institute in Naples, Florida, sitting right next to Grand Sport chassis 004. Another one ended up at the Simeone Foundation in Philadelphia, which Dr. Simeone acquired from collector Jim Yeager, along with Grand Sport 002, the only one out there that still has an original unrestored body on it. When a Grand Sport comes up at auction, and that almost never happens at this point, you're looking at north of $3 million. Now, if you think about the DNA this engine left behind, it's significant. Four-bolt main caps, dry-sump oiling, lightweight aluminum castings, all of that filtered down into the small blocks you could walk into a Chevy dealer and buy decades later. But in 1963, these were 12 hand-built, semi-illegal engines poured by a company that swore it wasn't racing, wired up to prevent tampering, and ordered destroyed the moment the wrong people found out. And the legacy from those 12 blocks outlasted every executive and every memo that tried to bury them. Now, let me know in the comments down below what you would do if you had one of those 12 blocks in your garage. Would you build it up and race it the way Duntov intended, or put it behind glass and never let anybody touch it? And if any of you have ever been to Revs or Simeone and seen one of these in person, I'd love to hear about that too. Otherwise, though, thank you all for watching. If you enjoyed this one, please make sure to like, share, and subscribe. It really does help me out. And I will see you all in the next one, Enthusiasts.