Indy Cylinder Heads - 535-Inch Bracket Monster

In the November 2012 issue of Mopar Muscle, we began building a bracket engine for the '72 'Cuda owned by local Mopar enthusiast Jim Freed, by assembling the bottom end of a 535-inch big-block. In this month's issue, we'll top this durable short-block with Indy Cylinder Head's 440-1 cylinder head and intake package, and dyno tune the engine for power and reliability.

Big-block Mopar engines are known for making big torque and horsepower. What many off-brand racers don't realize, however, is how reliable these engines can be. For the bottom end of this big-block, we chose a cast-iron Mopar Performance siamese bore block, and filled it with a rotating assembly from Scat Crankshafts. The 4.25-inch stroke crankshaft and forged H-beam connecting rods will easily handle the power and rpm this engine will make, and we opted for optional Mahle forged pistons, which are a nice blend of strength and light weight.

The cylinder heads are vitally important and must be able to flow enough fuel and air to support the engine's relatively large 535-inches. Available in several configurations for both the low deck B block as well as the higher deck RB block, Indy's 440-1 kit includes everything needed between the block and carb, and is economically priced, especially when compared to purchasing each piece individually. Even in un-ported form, these heads have been shown to add up to 100 horsepower to a properly built 440, which is difficult (or impossible) to achieve with any factory big-block cylinder head.

For our 535-inch engine, we selected the 440-1 CNC 345 heads along with Indy's aluminum single-plane intake manifold. As an upgrade, we opted for Jesel rocker arms, which incorporate pairs of rocker arms mounted to individual shafts. These rockers require the top surface of the cylinder head to be machined to attach the Jesel mounting plates, and can eliminate the need for external oiling provisions normally required with the 440-1 heads. The Jesel rockers can be oiled by either spray bars mounted in the valve covers, or, as in our case, they can actually be oiled through the pushrods from the lifters. Oiling through the pushrods is somewhat simpler, with the only sacrifice being a reduction in idle oil pressure. Fortunately, the big-block Mopar oiling system supplies plenty of oil volume to critical engine parts, so a reduction in idle oil pressure isn't a concern, especially in a race engine like ours.

With our short block complete, we bolted the cylinder heads in place utilizing ARP head studs and Cometic multi-layer steel gaskets. We've had great luck with Cometic head gaskets, finding them to seal as well as copper gaskets without the requirement of stainless-steel o-rings around the cylinders. Cometic does require a fairly smooth finish on the deck of the block and cylinder head sealing surface, so make sure your machine shop can meet this requirement prior to purchasing any MLS gasket. Fortunately Auto Performance Engines is equipped to machine the surfaces to the proper finish, so this wasn't an issue. As an alternative, we've found Cometic gaskets to seal well with a standard finish on the deck and head, so long as a small amount of silicone is used around the water jackets. It is certainly better, however, to machine the surfaces to the proper finish.

With the heads in place, we assembled our Jesel rocker arms and bolted them to the cylinder heads. Jesel shaft mounted rockers set the standard in valvetrain stability, and while they may be slight overkill for an engine like this one that won't see rpm over 7,500 the Jesel rockers will ensure this engine is durable and will require very little maintenance. The Jesel rockers are lightweight as well, further enhancing valvetrain stability and reducing the tendency for the pushrod to flex during valve opening.