The traditional small-block has been built in just about every configuration you can imagine, but sticking with a proven combination is a surefire path to great results. Take for instance the small-block Chevy featured here. Built by Chris Henderson of Henderson Power Sports, the engine follows a formula that is long established. Using a factory 400 production block as the basis, Henderson didn't alter Chevrolet's basic layout, but instead put together the familiar 406 combination arrived at by retaining the factory 3.75-inch stroke and simply refreshing the OEM 4.125-inch bores with a .030-inch overbore. One of the key advantages of going this route is that aftermarket parts are readily available as off-the-shelf parts, greatly reducing the costs compared to going with a more esoteric combination.
To serve as a foundation, Chris Henderson started with a production block as a base. Pulle
As Henderson tells us, "The block came out of a 1976 Chevy Blazer that was left out in a field so long, a tree was growing out of it. An aftermarket block would have been nice, but the stock GM block probably saved over $1,000 when all was said and done. The GM blocks are plenty strong for this kind of build, and with their siamesed bore there is plenty of meat between the cylinders to keep things stable. We just reinforced the original two-bolt main block with aftermarket billet main caps, and added a partial fill with Hardblock. The two-bolt main blocks are a better starting point than the four-bolt block, since the aftermarket splayed caps are a stronger setup than the factory four-bolt main's." Besides the usual machining, block prep included general cleanup and grinding of the casting flash and adding stand-pipes to direct oil flow to drain back to the rear of the block. Henderson tells us, "I wanted the oil to drain to the rear to keep the oil off the rotating assembly and reduce windage, and off the shallow side at the front of the pan."
While the factory crank measures 3.75 inches in stroke, Henderson opted to go with a Scat aftermarket crank in the same specification. The Scat forged crank is definitely a higher grade material than the OEM piece, but as Henderson points out, "The design of the counterweights and throws is much cleaner and shaped for a reduction in windage, and the surface of the crank is far smoother." Henderson departed from the OEM formula when selecting rods, steering away from the factory short rod arrangement, instead substituting a set of 6.00-inch Eagle H-beam rods. These rods are definitely strong enough to take the punishment, and the added rod length cures the compromised rod angularity problems inherent in the factory Chevy 400. Both the crank and rods are installed with Speed-Pro bearings, specifically coated to gain an extra measure of protection under load.
Owing to the common internal configuration of a stock stroke, 6-inch rod small-block, piston selection for this build was wide open. The .030-inch overbore block's cylinders were readily filled with catalog shelf pistons from CP. Henderson went with CP's Bullet series forged flat-top pistons, which come machined for a 1.5/1.5/3mm ring package. Henderson had the pistons modified by CP with a shallow reverse dome machined into the crown, matching the shape of the engine's AFR cylinder heads. Filling the ring grooves are a set of Total Seal rings, featuring Total Seal's proprietary gapless top design, and a Napier-faced second ring. Henderson remarks, "I like the Total Seal rings because of the superior sealing. Just trying to bar the crank around you'll find that it will practically stop cold at TDC because of the compression seal. There is also a better seal on the induction stroke, which pulls a little harder on that side."
Billet steel four-bolt splayed main caps replaced the two-bolt originals for added bottom
Holding the oil is a Moroso deep sump drag racing–style pan. The deep pan keeps the oil aw
A look inside the lifter valley shows Henderson’s detailing to this area and the stand-pip