Chevrolet 406 CI Small Block Build - Chevy Small-Block Power

An observer of high performance once proclaimed: “Look stock and carry a big arm.” Everyone wants more power, and Bow Tie hot rodders are famous for always pushing the horsepower and torque envelopes. But horsepower costs money, and unless your name is Bill Gates or Donald Trump, few of us have as many of those greenbacks as we’d like. So the ultimate engine story is where we show you how to make more power for less money. If that’s your Holy Grail, then you’ve come to the right place.

The reference to the big arm is a direct endorsement of displacement. You want a stronger Mouse trap? Build it with cubic inches. So while it is possible to build a 350 less expensively than a 400 small-block, those extra inches make it all worthwhile. This story is all about pumping steroids into what once was perceived as a weak-kneed small-block. But we like to think of our version as Muscle Mouse, for obvious reasons. If you think that 500 lb-ft of torque and 450 hp from a pump-gas small-block is talkin’ your kind of small-block, then pay real close attention to the details.

Most of the engines we deal with in this magazine are intended for street performance and mild competition use. Therefore, it’s the combination of torque and horsepower that makes an engine powerful. Peaky engines are no fun on the street. Our goal with this 406 was to make serious torque with iron cylinder heads and a dual-plane intake manifold—in other words, a working man’s motor that could embarrass those Mustang 5.0 guys as well as those young studs with their turbocharged front-driver imports.

The only assumption that we made in this story is that you can dig up a suitable two-bolt main 400 block. These blocks are becoming increasingly harder to find than an alibi your wife/girlfriend hasn’t already heard. Given this difficult situation, the alternative is to drop back on the displacement curve slightly by substituting a 350 for the 400 block and build a 383. The Scat crank and rods we used will work equally well in either of these applications. Scat also sells an internally balanced crank that doesn’t require an externally balanced damper and flexplate like the 400. This reduced-fat displacement option will cost some power, however. Everything else being the same, a 383 version will cost you roughly 40 lb-ft of torque and 25 hp. These are rough numbers but certainly realistic.

One key to this buildup is the Scat cast crank and rod package. The crank sells for $299 while the strong 4130 steel I-beam rods go for a mere $249. Together that’s only $550. Combine that with a set of Speed-Pro forged pistons for roughly $400 and for under $1,000 you have a rotating assembly that’s as strong as it is inexpensive. There are certainly other ways to go, but we think this is one of the best for the money. We’ve combined this with a set of budget-based Dart Iron Eagle 215cc cylinder heads and a Comp Cams valvetrain, and as the dyno test reveals, this is one kick-ass package. Let’s see how it all goes together.