LS7 Unplugged

There's a windage tray beneath the oil pan. It is notched to clear the oil pan's suction tube.

The LS7 has a unique, PF48 oil filter that incorporates an internal bypass valve. The filter is the same size as the common PF44 oil filter, but its thread pitch is different so the PF44 can't be mistakenly installed.

The cylinder heads are artfully crafted, CNC-carved blocks of aluminum with cavernous, super-straight tunnel ports. It's hard to believe this a factory-production part.

The heads' combustion chamber volume measures 70 cc and the chambers are fed by gigantic and lightweight titanium intake valves with 56mm faces. The intake valves have 22 percent more area than LS2 valves, but weigh 21 grams less! The exhaust valves are 41 mm across and are sodium-filled.

The heads are placed on multi-layer steel (MLS) head gaskets; they're tall, too. The ports are long to enhance velocity and the valvetrain is a little taller. In fact, the rocker rail is a full 6mm taller than the LS2's (approximately 0.25-inch).

The valve angles of the LS7 are 12 degrees (versus 15 degrees on the LS2). Accommodating this specification and leaving room for uninterrupted flow in the ports requires offset rocker arms on the intake side. Note that the rocker arms are not roller-tipped.

All the bolts of a cylinder head are run down and torqued by one of the big, computer-controlled tools. Each of these tools costs about $150,000, and there are several located along the production line.

The valve covers look similar to other Gen III and Gen IV engines, but with a big difference: the only oil fill port (passenger side) is designed for "fill it once and forget it" use. Except for an oil feed during balancing, the engines leave the PBC dry. They are filled at the offsite hot-test facility and capped with a permanent seal. For the car owner, oil must be added to the dry sump tank. There is no dipstick on the engine or oil pan, either.

The intake manifold, throttle body and fuel rails are delivered as a single part and installed as such. In GM jargon, the unit is called an Integrated Air Fuel Module (IAFM). The fuel rails are the same as the LS2, but the injectors are rated for 40 lb/hr. The IAFM assembly is supplied by Bosch.

The exhaust manifolds are installed on the assembly line, a procedure not always performed on engine lines. We're told the manifolds will bolt up to an LS2 engine, even though the exhaust port shape isn't quite a match--the LS7 manifolds' ports are larger, so there's no worry in blocking the flow path.

A rarity for production engines--and even racing engines--the exhaust manifolds are made from hydro-formed tubular steel. The individual runners of the header tubes meet at a unique quad-outlet collector, which is said to smooth exhaust flow and reduce backpressure.

Ignition coil packs are the same as those on the LS2, which are upgrades from the Gen III design. They're a little smaller and more efficient, but deliver the same spark energy as the previous-style coils.

This shot depicts the final assembly of the LS7 engine. At this stage, it is given a thorough inspection by the builder and a log of the torque sequences, and bar code-scanned procedures are checked. A second inspector who had nothing to do with building the engine will also look it over because a fresh pair of eyes will find things the first person might have missed.

An LS7's last stop in the PBC is the balancing room. The engine is fired up on natural gas fed through the throttle body. The engines are run briefly at 1500 rpm to produce baseline reading. The balance cradle is suspended on a cushion of air when the engine is running. Weight is added to the flywheel or balancer, as needed, with tolerances held at 0.5 ounce.

After balancing, the engine is sent offsite for hot testing, then returned for shipment to the Corvette's Bowling Green, Kentucky assembly plant. This one is ready for an awaiting Z06 body.