Since we're going to use forced induction, piston strength against detonation was far more important than squeezing out an extra couple of horses. In order to accommodate the larger rings and ring land, the oil scraper ring was moved down toward the free-floating wrist pin. In this case of this particular design, the oil ring groove partially intersects the pin bore, so a rail support ring is used below the oil rings and expander to support and prevent the rings from excess movement.
A dished-type piston changes compression and increases the volume of the combustion chamber. JE also machines in valve reliefs specific to the angles of the intake and exhaust valves, so its pistons are bank-specific (unlike stock). The valve reliefs are cut deeper for added lift and duration.
To take the extra bending load of higher cylinder pressures, the stock forged steel connecting rods were replaced with forged E-4340 chromoly crossbeam-style connecting rods from Pauter. Unlike the OEM I-beam rod, which is manufactured by using powdered metal forged together in a cost-saving process called sinter forging, Pauter uses a one-piece conventional forging process. This ensures continuous grain flow and starts with a billet piece of 4340 steel that is forged, shot peened for additional surface hardness, CNC machined and balanced to within a gram.
OEM-type rods also use snap caps, where the bottom half of the big end is intentionally broken off after being forged. While this offers more surface area to hold the rod cap onto the rod, it's done primarily to save time and machining costs. The Pauter rod uses caps that are cut off from the original one-piece rod forging and then bored to the proper journal diameter and fitted with pressed rod cap alignment sleeves to ensure an exact fit.
Pauter's crossbeam geometry is designed to increase bending strength in the direction of engine rotation and distribute the load over the whole, beefy cross-sectional area of the rod. It also has better windage properties than H-beam designs. We ordered our rods with the optional oiling channels on the journal end, which provide a path for oil to escape from the journal and make room for fresh oil to flow, while at the same time throwing the exiting oil toward the bottom of the pistons and wristpins.
The stock bearings were replaced with ACL tri-metal Race Series bearings that use a copper, lead and P76 overlay alloy, increasing load-carrying capacity as well as temperature tolerance. Lead helps the bearing's embedability (as well as prolong service life) without compromising wear on the crank or bearing itself. While it would have been a good time to lighten and knife-edge the stock forged and counterbalanced crankshaft, we left it alone to maintain street driveability and avoid issues with engine harmonics.
The Top End
While the engine was torn down, we also installed a set of Jim Wolf Technology 0.456-inch (11.6mm) lift, 261-degree duration (at 0.005 inches of lift) C2 intake and exhaust camshafts. These cams were specifically designed to work with the VQ's variable intake cam phasing system on forced induction applications to accommodate added airflow at mid and high revs while eliminating the excess duration and overlap of the stock NA cams.
The C series is intended for modified valvetrains, which use JWT harmonically matched valve springs (which allow for the minimum design spring pressure), while its S (or Street) profiles are engineered to work with stock valve springs. JWT also provided us with single-wound valve springs 30 percent stiffer than stock, with a higher natural frequency than dual springs, due to the larger wire diameter, which eliminates spring surge. Other valve springs can be as much as 80 percent stiffer than stock, which adds excess load and wear to the valvetrain, causing parasitic power loss.
By Jay Chen
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