The chambers of the LS7 heads...
The chambers of the LS7 heads were absolutely untouched from the factory. GM engineers worked long and hard to get the design this efficient in a mass produced engine. The double-quench design was an evolution of the heart-shaped wedge. Champion racing spark plugs like these angle-electrode versions were used by a number of competitors at the EMC for the quality and performance they offer.
Mahle has been supplying high-end racers with top-notch pistons for years and since introducing their Power Pak piston/ring packages a few years back at a budget price, they have really taken over in the world of moderately priced street/strip engines. A low-tension metric ring package and short skirts coated with an anti-friction Teflon-based coating were big factors in Bowers' choice of Mahle for their pistons. They were used out of the box, save for some minor valve notch clearancing that was required for the big LS7 intake valves.
Did we not mention the LS7 heads? Bowers picked them up as bare castings on eBay for just five Bennies. Saving enough from not buying the heads complete, he was able to score a set of big-block sized 2.200-inch Manley intake valves and 1.540-inch exhaust valves to use in the heads. Manley was also the source for the polished Nextek springs, retainers, and locks, keeping those valves in check.
LS7 heads were, of course, available on the Z06 Corvette, and came with giganto CNC-ported runners, Titanium valves, and flow numbers that make 18-degree small-block guys want to throw rocks at their high-dollar engines. Since the RED engine was designed to make big average torque and horsepower numbers from 3,000 all the way to 7,000 rpm, they decided to shrink the runners down from around 250 to 238cc with carefully placed epoxy. Final hand blending of the runners was the only other modification to the heads. They felt that the combustion chamber design was perfect to begin with, so they never even touched them. Fel-Pro MLS head gaskets and ARP head bolts joined the heads to the short-block.
The bling under the valve...
The bling under the valve covers shines like a disco ball. Even though they were standard fare for the LS7, Titanium valves were prohibited in the Challenge, so a set of Manley valves were used with RED's custom 52-degree valve job. The only exotic metal allowed was Titanium valvespring retainers, which the team also sourced from Manley.
Acting as a mechanical ECM for the engine was a custom Bullet solid-roller cam with aggressive lobes urging the COMP Cams roller lifters. Thanks to the factory location of the runners and offset rocker arms, they were able to use 3/8-inch diameter pushrods to minimize harmonics and maximize ultimate lift. Surprisingly, the Harland Sharp roller rockers fit under a set of stock valve covers with just a touch of clearancing on the tips. With the correct valvetrain geometry set, the crew didn't have any issues on the top end.
A quick search for GMPP PN 88958679 produced a number of retailers offering the front drive distributor conversion kit for the LS engines. The kit not only includes the timing cover itself but a fuel pump eccentric for use with a mechanical fuel pump, a distributor drive gear, spacers, bolts, and a crankshaft seal. With the conversion kit in place, all that it takes is a small-block Ford distributor (cough, cough), like the MSD Pro Billet dizzy that Bowers scrounged to get fire in the hole. Feeding the flame was an MSD Digital 7 ignition box and HVC II coil.
An advantage of using the...
An advantage of using the truck oil pan in this competition is that it is deep enough up front to use a full-length windage tray, where the F-body pans only use a 3/4-length tray to clear the crossmember. Also, the truck pan with its deep sump keeps the majority of oil far away from the crank while spinning.
With compression and ignition taken care of, the final element of the internal combustion triangle was fuel. Shell V-Power 91-octane pump gas entered the Quick Fuel 4150 carb and thanks to our friend Bernoulli, was drawn through the main jets, emulsified with air pulled through the air bleeds, and atomized as it exited the annular boosters. The 1,050-cfm unit uses a three-circuit design that allowed Bowers and teammate Jason Gonzalez to tailor their fuel curve to their liking both at their mile-high shop, and at the near sea-level conditions of the University of Northwestern Ohio-based Challenge. Since tuning is such a big deal in getting the most out of a combination like this, they spent quite a bit of time dialing it in at home. "It had a five-hole emulsion bleed in the metering block, and we were blocking the lower two, then we were blocking just one, and we were trying to straighten out the curve on the top side and we got it pretty good."
With the air/fuel mixture perfectly homogenized, it passed through the two-piece intake manifold that is, by itself, a work of mechanical art. The intake was designed by Performance Induction with a large plenum to feed a good-sized engine.