409 Chevy Engine - 481-Inch 409 Stroker

While Chevy never employed four-bolt main caps on the 409, no chances are being taken on this one. Custom machined billet steel center main caps use stock outboard bolt locations and tap into beefy block webbing for inboard fasteners. The material is there; we wonder why Chevy never took advantage of it. Heck, even the hard-core race-specific '62/'63 Z-11 427 W-motor had two-bolt mains.

Though reconditioned stock 454 rods (left) can be used, at $320 a set, forged steel Eagle I-beam rods (right) are generally less expensive. They measure 6.135 inches-same as the stock 454-and feature bushed small ends. Total weight is 789 grams, only 12.1 grams more than the Chevy rod despite bigger 71/416-inch cap screws and wider beams.

Though new 409 pistons are available, the customer wanted to reuse his rare, vintage 0.060-inch-oversize TRW forgings. To reduce piston-to-wall clearance, Lovatt hard-anodized coating was applied. In addition to reducing friction and minimizing future wear, the coating adds 0.003 inch to the overall diameter. It's a great way to save used pistons. The ring lands and wristpin holes are masked to maintain stock width and diameter dimensions.

One problem with 409 pistons is the fact that one half of the dome is much taller and heavier than the other half. The undersides of the thick crowns were milled to remove mass and partially correct the lopsided weight distribution.

Never use stock replacement 409 cam bearings if valvespring pressure exceeds 350 pounds-they'll smear. The solution for the 515-pound springs used in this engine is a set of modified Durabond '55-'63 Chevy small-block cam bearings. Available as PN CHP-4, the first four are a direct fit in the 409 block except for the No. 5 bearing. Three 11/44-inch oil-feed holes must be drilled in the positions shown by the mini-screwdrivers. Be sure to index the twin stock 11/48-inch feed holes (pen points) toward the solid part of the cam bore housing to close them off; the trio of new holes takes over. Also be sure your camshaft has a fully grooved rear journal, or oil feed to the lifters galleys is restricted.

This shot illustrates the 409's hidden secret. Chevy cut the block deck surface at a 74-degree angle instead of the usual 90 degrees found on most other V-8 engine designs. The wedge-shaped areas at the top of the cylinders are the combustion chambers. Piston and ring installation is facilitated by factory-issue 0.060-inch-oversize reliefs encircling each bore, giving the ring compressor room to work and a shelf to settle on. The rings are standard-tension Total Seal PN CR9190-130. If the block is bored oversize, these reliefs must be remachined, or you'll never get the rings past the tops of the bores.

Like most engine designs, the rod big-end width is not even. The wide side (pen points) goes toward the crank cheek, the narrow side toward the other rod in the pair. Rod side clearance is 0.022 inch; Eagle bolts torque to 65 lb-ft. Rod bearings are Clevite 77 CB-743P-20 for big-block Chevys. Main bearings are semigrooved Federal Mogul 4036M.

The piston quench pads sit 0.018 inch below the flat cylinder-head surface. (The pen points to the combustion chamber.) Piston and rod orientation is critical. Because of the way the valves are positioned in the head, the No. 1, 4, 5, and 8 pistons have different valve clearance cutouts from the 2, 3, 6, and 7 pistons. Mix them up and you'll eat valves! The Mercury-Edsel-Lincoln 430 V-8 and many diesel engines use a similar chamber-in-block design.

Isky supplied an RR-639/260 solid roller cam to complement the added cubic inches. Specs are 0.639/0.639 lift, 294/294-degree advertised duration, 260/260-degree duration at 0.050, and 110-degree lobe center. Hot valve lash is 0.028/0.028 inch. Engine builder Scott Emley uses Ford Racing M-19579-A991 cam-and-lifter prelube on all surfaces because it's supersticky and clings like mad.