While the Generation IV was based on the Generation III design, it was developed with displacement-on-demand in mind. This new LS2 technology would allow four cylinders, in alternating fashion from side to side and front to back, to be deactivated. This Gen IV engine was also designed to accommodate variable valve timing. None of this was ever used on the Corvette, though. Maybe someday?
A three-valve-per-cylinder head was originally slated for the LS7. That would have been a first for a GM pushrod engine. In the end, though, the idea was shelved because of design complexities. Besides, the basic two-valve configuration proved to be enough to meet the LS7's goals.
It's interesting that the LS3 came after the LS7. While the LS7 was designed for the Z06, the LS3 was built as a base motor to replace the LS2. A lot of new things were done with this motor. The most obvious was the increase in displacement, but the LS3's new cylinder heads may have been even more important. These new heads were based on the large port design used on the LS7 motors and featured larger and straighter ports, not to mention larger valves. All of this was coupled to a new intake manifold. Basically, the LS3 was a brand new engine, with only its basic architecture similar to the LS1 of 1997.
The latest chapter in the LS saga is the mighty LS9. This may be the ultimate LS engine. I seriously doubt if anyone considered a supercharged LS engine back in the early '90s. If they did, they were very quiet about it.
The LS9's 638 hp is surely impressive, but the 604 lb-ft of torque is even more astonishing. This engine took a long time to develop and may be the high point in the development of a gasoline powered Corvette. It's been a long journey from that press conference in New Jersey.
Today there is a Generation V someplace in the GM system. The gossip says that it's an overhead-cam engine with four valves per cylinder. It will feature variable valve timing and cylinder deactivation. This will obviously be a truck engine, but there could easily be a Corvette version. After all, the Corvette has done rather nicely with all of these high performance truck engines over the years.
The C5-R Cylinder Block
You probably haven't seen this engine. Actually, you may never see this engine in person. It was developed for the factory-backed Corvette Racing program. The C5-R cylinder block has been manufactured in very small quantities since 2000. Part of the reason for the low production numbers is that you have to pay more than $8,000 for just the bare block.
These engine blocks are manufactured with a unique 356M aluminum alloy for greater strength. They also undergo a variety of specialized machining and inspection processes, including a process known as "hipping." Hipping is a multistep heat-treating process that pressurizes, heats, and then cools the block to ensure strength and eliminate porosity.
A Siamese-bore design with 4.117-inch finished bores enables 7.0L (427ci) displacements. The C5-R uses billet steel main caps with premium 4340 fasteners. Racing-quality head studs are also included. All LS series heads will work with the C5-R block.
One reason (or at least a rumored reason) for the high cost of this block is that around 20 percent of them are rejected because of quality issues. It's not that the blocks are that bad. It's just that the standards are that high.