It's big. When the decision was made to build the 2014 AMSOIL/Street Rodder Road Tour 1959 Chevy Impala, everything had to be upsized. The car is monstrous, the trunk can easily accommodate a small college marching band (minus the tubas), and the wheels and tires are proud of their illusions of grandeur. So it goes without saying that the engine would have to be equally as momentous. That inferred a big-block Chevy or perhaps a W engine.

But this is 2014, not 1965. So something new means LS power with EFI; the call went out to Ron Shaver (the patriarch of Shaver Racing Engines). He said he could build a 427 that would fulfill all the prerequisites of big power, be very streetable, and still be enticing to the eye. We're here to tell you this big dog hunts on all counts. The old standard for a street performance engine used to be 1.1 horsepower per cubic inch (hp/ci). This RHS block–based 427 blows that out of the water with an impressive 1.45 hp/ci with its 622hp peak. Even better, this pump gas performer does it with respectable idle quality, outstanding throttle response, and a power curve that will demand you flatten that skinny little pedal on the right as often as possible. Diplomatic immunity might be a requirement to drive this car.

All this magical power didn't happen accidentally. The first rule was to not cheap out. Shaver could have used a production block, but the commitment to quality demanded the near-legendary RHS aluminum block as its foundation. We combined the RHS block's cornerstone with a durable rotating assembly from SCAT, Mahle pistons, an outstanding set of CNC-ported heads from Livernois, an over-achieving valvetrain from COMP Cams, and an absolutely stunning Inglese 8-Stack Induction System to come up with the ultimate street engine. Please excuse us if we gush a bit, but a mild big-block Chevy 502, for example, can make an impressive 570 lb-ft of torque at 4,200. The Road Tour 427 thumps out over 600 lb-ft at 4,800 rpm and does it while trimming 200 pounds. And we're doing it in style. Let's see how our Road Tour 427 all came together.

Building Blocks

It wasn't long after the LS engine made its debut in 1998 that Corvette escalated the horsepower game with a 4.125-inch bore 427 dubbed the LS7. Since then, the 427 has become the de rigueur displacement for powerful LS street engines. While GM sells a 427 production block, for the Road Tour 1959 we opted for the top-of-the-line RHS aftermarket block. The block comes in several configurations but Shaver spec'd the standard deck height 4.125 finished bore assembly that would also easily accept the 4.00-inch stroke crank necessary to complete the 427 combination. The RHS block includes longer cylinder sleeves to accommodate the longer stroke, which avoids the difficulties stemming from shorter cylinder lengths in the LS2 and LS3 OE blocks.

RHS blocks also feature a 0.388-inch raised cam bore centerline to ensure it can clear even the longest stroke crank. That requires a longer chain that COMP provides. The cross-bolted mains and deep skirt block also increases windage passages to minimize windage difficulties that can occur with longer stroke LS engines.

Combined with a priority main lubrication system with reduced restrictions, this block can easily accommodate much bigger power numbers, which means it promises to make power for a very long time.

The rotating assembly is also up to the challenge with a SCAT forged steel 4.00-inch stroke crank and I-beam forged 6.125-inch connecting rods that Shaver fitted to a set of Mahle flat-top 4.125-inch bore pistons with matching Mahle rings. The cam is a COMP hydraulic roller with mildly aggressive specs but even when combined with the rectangle port heads by Livernois, this engine doesn't sacrifice torque to make horsepower.

1. Many pretty engines are just that–attractive but a little short on real power. The AMSOIL/STREET RODDER Road Tour LS 427 is a rare combination of statuesque good looks combined with eyeball-flattening power. At 620-plus horsepower, Dean Livermore of Hot Rods by Dean is making final adjustments; after dropping it into the Road Tour 1959 Chevy he thinks it will get the job done.

2. We needed a strong foundation for the Road Tour 427 and it doesn't get much better than an RHS standard deck height alloy block. The RHS block comes with priority main oiling, which means the mains and rods get oil first. The block also has a raised cam centerline to clear big stroke cranks.

3. A big advantage with the RHS block is spun cast-iron liners that ensure excellent ring seal. We didn't need them, but you can see that the block can accept six-bolt cylinder heads. A standard deck RHS block can accommodate a stroke up to 4.250. With this 4.125-inch bore, that's 454 inches.

4. A forged steel crank is the only choice for an engine like this, so we selected a SCAT forged steel crank and matched it with a set of SCAT I-beam rods.

5. Mahle makes an excellent 4032 alloy flat-top piston for the 427 that includes a nice coating on the skirts. The 4032 alloy does not expand as much as 2618 alloys for a tighter piston-to-wall clearance. This makes for a quiet engine during warm-up.