Mean Mouse: Chevy 406

Although we retained the stock stroke, we used an aftermarket 4340-forged Scat crank and CAT Power 5.7-inch H-beam rods. These rods mandated a little block clearancing down low. The milled area (A) is necessary to clear the bigger “big end” of the H-beam rods, and the circular relief (B) allows clearance for the rods’ cap screws. Notice the smoothed edge on the bottom of the cylinder wall. Lambeck worked overtime with the die grinder to ensure the piston skirts wouldn’t hang up on sharp edges in the bores. Finally, the distributor shaft hole is chamfered so MSD distributors’ O-rings won’t tear. Lambeck’s engines are pricey, but you get what you pay for with this kind of attention to detail.

Lambeck mounted a dial indicator on the end of the crank and bolted up the rear-main cap to check how far the crank “walked.” If it’s in excess of 0.0005-inch, there could be a binding problem. We saw no measured movement on our Scat crank, so Lambeck lightly scuffed the Clevite 77 bearings with a Scotch-brite pad, re-washed them, and dropped the crank into place. Don’t forget that the 400 uses a unique rear seal.

Here’s a seriously stout bottom end. You can see the drilled areas where the crank was balanced. See the pointed edges on the faces of the counterweights? This is one of Scat’s lightened cranks; while it’s not really necessary at this power level, its reduced inertia should come in handy if we ever swap to a high-winding solid-roller valvetrain. Milodon studs were installed finger-tight in the load-bearing inner cap locations, and the nuts torqued to 50 lb-ft, then 75 lb-ft from the center cap outward. Lambeck loosened, repositioned, and retorqued a couple of the caps until the crank spun freely, then torqued the side bolts to 40 lb-ft.

You’re not done yet! Our hard-core SFI-approved ATI Super Damper does require a slight hone to achieve the correct press-fit on the crank snout. ATI specifies that the damper’s crank hole should measure 0.0009-0.0012-inch smaller than the crank snout.

Hand-fitting piston rings is part of any quality engine buildup, and it’s paramount for high-performance mills. The JE piston rings were gapped to 0.018/0.020 inch (first/ second ring) with the help of an electric grinder and a ring installation tool that ensures squareness in the bore.

The rods were Spirolock’d to the SRP flattop pistons (using plenty of Torco assembly lube on the piston pins), and the piston/rod assembly was bolted in and checked for deck height. The pistons measured 0.010 inch below the deck, which was exactly where we wanted it.

We chose a custom-ground Crane hydraulic roller cam, a tasty combination of maintenance-free operation and steeper, faster-accelerating ramps over a flat-tappet grind. Crane’s state-of-the-art CNC equipment enables them to grind your custom cam and get it shipped to you the following day. We chose a small–base circle grind to prevent rod interference on our engine. Crane’s roller cams come with a pressed-on iron gear that’s compatible with a standard distributor gear. But keep in mind you’ll have to run a bronze-tip fuel pump pushrod (shown) if you’re using a mechanical pump.

We wanted a low-10:1 compression ratio to keep the mill happy on a 91-octane pump-gas diet. Lambeck performed a quick compression check to verify our squeeze factor and came up with a surprisingly high 10.47:1 ratio. He switched to a thicker 0.051-inch compressed height gasket, which put us at a more comfortable 10.2:1.

Backed with a Torrington bearing that rides between the block and cam gear, our Milodon double-roller timing set freed up some parasitic friction, and also made degreeing the cam a little easier. Lambeck drilled out the cam gear drive hole to 13/32 inch to accommodate an eccentric bushing. After some fiddling with the bushing, one degree retarded had it dead-on. We bolted up a trick two-piece Mr. Gasket front cover to make future cam swapping less messy.

What happens when air flows from a smaller opening into a larger hole? Well, its velocity slows down, and the stagnant air near the port walls tends to behave unpredictably. Not good. A couple of hours worth of porting, and Lambeck had our Edelbrock Victor Jr. intake ports sized perfectly to mate with the head ports. Definitely not a bolt-on, but definitely necessary.

Our Holley HP750 bolted right on—in fact, it’s the single major component that wasn’t somehow modified before installation. We had to rejet it, but we’re not sure that counts!

It used to be a rule that building a high-horsepower engine meant compromising streetability, but that’s no longer the case. When we set out to build this 406ci Chevy small-block, parts selection was based on the end result of a strong, torquey street motor. Heck, the term “street” doesn’t even mean much these days, as some 7-second cars even claim “street car” status. Well, “street” to us means a manageable idle speed; decent vacuum to operate power accessories; detonation-free combustion on pump gas; and cool, steady operating temps. With that in mind, we retained the 400 small-block’s stock strobe, bored it 0.030-over, settled on a 10.0-10.4:1 compression ratio, selected a relatively mild hydraulic roller cam, and spec’d a set of heads to yield adequate port velocity for snappy throttle response. And we had the whole package meticulously blueprinted and assembled by Brad Lagman of Bob Lambeck Enterprises in Northridge, California.

Well, we got the streetable idle (750 rpm), good vacuum (13 inches), and stable temps (160 degrees) that we were looking for, but when we pinned the throttle at WOT, the resulting dyno graphs were unexpected icing on the cake. Have a look at what it takes to construct a streetable fire-breathing small-block, but realize that this particular engine build isn’t something that a novice should tackle. Every piece of this engine, save the block and the rearmost main cap, was an aftermarket piece. The carb and heads bolted up without any massaging, but practically every other component needed some type of modification before it could be used. The results obviously speak for themselves, but we’re just advising you to realistically assess your own skills before you think about duplicating Lambeck’s 406. With that in mind, we included a few of the more challenging mods—a few that you might even have overlooked—that Lambeck performed on our big-inch Mouse.