The dirty little secret about all the legendary Chevy engine builders of yore is that the base material they had to work with had a lot of room for improvement – a reasonably talented mechanic could take your average small block Chevy and double the factory horsepower without breaking a sweat. But with the dawn of the “LS era,” things suddenly got a lot harder. Intake and cylinder head design were actually pretty good, and power gains from tweaking on them weren’t as dramatic as they used to be.

Most readers will be quite familiar with Mast’s cylinder head offerings…

That makes what Mast Motorsports has accomplished with late-model GM engines all the more impressive. Their motto is “kicking ass since 2008,” and they are among an elite group of engine builders who have taken the damn-good-from-the-factory LS platform and made it superb. From cylinder heads to complete engines, they have helped raise the bar on what’s possible, and at this year’s SEMA show we got another good example of what they can do when given a blank sheet of paper.

The LS7 427 SS Black Label uses forged Mahle pistons in 4.125-inch bores, pushing a Callies Compstar crank and rods, topped by Mast’s 305 LS7 heads to grind out 700 naturally-aspirated horsepower. Of course the crowning showpiece of the 427 SS is the Hilborn individual throttle body EFI system, which utilizes throttle-by-wire control to provide drivability and power “under the curve” that those old-school builders struggling with eight-stack mechanical injection could only dream about.

Is it for everyone? Obviously not. But for the select few who need 700 all-motor horses and have no fear of hood clearance issues, this is one legendary powerplant that will stand the test of time.