Part 2: Building the Slant Six

At TDC, the piston is 0.180 below the deck. And despite our 0.546-inchlift cam and heavily-milled head (0.100), the clay test revealsvalve-to-piston clearance of 0.310 intake and 0.270 exhaust. That'sthree times the safe minimum.

Mopar Muscle tech meister Steve Dulcich talked us into using the EngleKV-1 solid cam and lifter set. We're glad we listened. Despite its wildspecs (see Recipe List), it has good street manners and is a perfectcomplement to the test car's 3,000-pound race weight, 3.55 axle ratio,9.2:1 compression ratio, and 2,700-rpm stall speed. We installed it 2degrees advanced after drilling the cam-gear dowel hole from 0.250 to0.270 and installing a 0.020 shim (flattened coat hanger) to re-indexthe gear on the cam snout. The single-roller timing chain and steelgearset is cheap but effective. Double roller alternatives are availablebut offer no benefit at this level of performance. By all means, avoidplastic-coated cam gears, as they tend to shed teeth with severe use.

The stock head needs help for performance use. Gregg Hansen of Stage VEngineering spent an afternoon relieving the bowl areas, enlarging theports, and gasket matching. Then, Gene Ohly milled 0.100 off the deck,reducing chamber volume from 54 cc to 44 cc, bumping compression to9.2:1 with the stock-replacement flat-top pistons. He also installedoversize hardened seats and bronze valve guides and performed athree-angle valve job. If you're building an aluminum block, tell yourhead porter not to back-cut the chamber walls adjacent to the valveheads to unshroud them. Doing so reduces the area available to pinch thehead gasket's fire ring and can lead to chronic gasket failure. Our headwas unshrouded slightly (note the 8 and 2 o'clock positions), but we gotaway with it.

The height of the valve guide bosses must be reduced for safe retainerand seal clearance at full lift. Oscar Alvarez at JMS Racing Engines cutours from .750 to .590 and also machined the outer diameter of thebosses to clear the valve spring's flat-wound inner surge dampers (seepointer).

The stock 1.62/1.36 valves are replaced with 1.70/1.44 stainless valvesfrom Egge Machine. The Pioneer S-1051 single with damper valve springshas an installed height of 1.750 intake and exhaust where it exerts 120pounds on the seat and 260 pounds at the cam's .546 maximum lift. Bycomparison, stock Slant Six springs rate 144 pounds at full lift(.371/.364 stock cam). Engle chrome-moly retainers replace the stampedsteel stockers, while stock Chrysler locks are reused. Neopreneumbrella-type valve seals control oil.

Like the main bearing caps, the soft aluminum block requires specialhead fasteners. The original reduced shank 7/16x14 bolts were lost, soAl Nichols and Mike Rose of ARP tooled up a new head-stud kit just forus and any other aluminum-block customers who might need a set. Theseheat-treated 7/16 studs can be threaded deeper into the block than boltsfor increased thread engagement, and they offer superior clamping force.Using antiseize compound, they torque to 60 lb-ft (iron blocks go to 75lb-ft). Aluminum blocks take a special head gasket that's only availableas N.O.S. and must be retorqued after initial startup. Remember toinstall the lifters before the head on all iron blocks. The open deck ofaluminum blocks allows for later lifter installation...

The rearmost rocker-shaft pedestal on all Slant Sixes is counter-bored(see pointer) to feed critical oil to the rocker shaft and rocker arms.It requires a specific 3-inch long hold-down bolt (on right). The otherfive hold-down bolts are 2 inches in length. Torque them all to 30lb-ft.

There is a lot of confusion regarding proper rocker-shaft orientation.Here, the pen points to one of the 12 oil-squirt holes that lubricatethe valve stems and rocker arms. They must be targeted at the driverside of the engine or valve-tip/rocker-pad failure will result.

They may not look sexy, but the stock 1.5:1 stamped-steel rocker armsare an engineering marvel and are fully capable of living with our hotcam and stiffer springs. The same goes for the stock 9.984-inch long,5/16-diameter pushrods. Despite the hefty head milling, the stockadjusters can take up the slack without introducing geometry problems.If both the block (iron only) and head are milled, shorter custompushrods would likely be required. We set the valve lash at .010(I)/.020 (E) cold with iron or aluminum blocks and check it every monthor so.