Repair-It

It was born after a small group of engineers within BMW secretly discussed the possibility of building an engine even bigger than the 750iL's regular-production V-12. Apparently, the group settled on the number 16 for the new engine's upper-limit cylinder count; the lower limit, it was determined, was a baby three-cylinder version of the same engine. (We know, way less interesting. ) The project was undertaken to show the versatility of BMW's engine family at the time.

The 6.7-liter V-16, internally referred to as ED-173-1, was pretty much BMW's normal 5.0-liter V-12 enlarged with another four cylinders added to one end. It was first put on a dynamometer in January of 1988, where it was found to make "only" 406 horsepower. While that power, back then, was truly incredible, these days there are four-cylinder engines in regular production that make as much (and the quad-turbo W-16 in Bugatti's Chiron makes up to 1500 horsepower). Anyway, the V-12 in the normal 750iL made 296 horsepower, meaning the addition of a third more more cylinders added about third again more horsepower. Talk about a linear scale!

3.90 in bore blocks[edit]
5.7 L
LT5

For model year 1990, Chevrolet released the Corvette ZR-1 with the radical Lotus Engineering-designed double overhead cam LT5 engine. Engineered in the UK but produced and assembled in Stillwater Oklahoma by specialty engine builder Mercury Marine, the all-aluminum LT5 shared only the 4.4 inch bore spacing with any previous SBC engine. It does not have reverse cooling and is generally not considered a small block Chevrolet.

Used only in Corvettes,[26] the LT5 was the work of a team headed by Design manager David Whitehead, and was hand built by one headed by project engineer Terry D. Stinson.[27] It displaced 5.7 L; 349.5 cu in (5,727 cc) and had a bore x stroke 3.90 in × 3.66 in (99 mm × 93 mm) instead of the usual 4 in × 3.48 in (101.6 mm × 88.4 mm) and featured Lotus-designed DOHC 4 valves per cylinder rather than the usual Chevrolet 16-Valve OHV Heads. The preproduction LT5 initially produced 385 hp (287 kW), but was reduced to 375 hp (280 kW) and 370 lb⋅ft (502 N⋅m) for the 1990-1992 Corvette ZR-1. The power ratings jumped to 405 hp (411 PS; 302 kW) at 5800 rpm and 385 lb⋅ft (522 N⋅m) of torque at 5200 rpm from 1993 until its final year in 1995,[28] thanks to cam timing changes and improvements to the engine porting. 1993 also added 4-bolt main bearing caps and an exhaust gas recirculation system.

A second generation of the LT5 was in the testing phase as early as 1993. What little information survived showed that it would have used a dual plenum system similar to the first generation Dodge Viper as well as variable valve timing. The next generation LT5 was set to produce between 450 hp (336 kW) and 475 hp (354 kW). Unfortunately, the cost to produce the LT5 along with its weight, dimensions (would not fit the C5 pilot cars without extensive modifications) and internal GM politics over using an engine that was not designed and built in house killed the LT5 after six years of production. GM canceled the ZR-1 option beginning model year 1993. Engines that were to be installed in the as yet unbuilt ZR-1's were sealed and crated for long term storage. After they were built at the Mercruiser plant in Stillwater, Oklahoma they were shipped to Bowling Green, Kentucky and stored in the Corvette assembly plant until the 1994 and 1995 ZR-1s went down the assembly line. A total of 6,939 cars were produced.[29] The LT5 however wasn't an evolutionary dead end. Despite being discontinued, a new class of premium V8s for Cadillac and eventually Oldsmobile, the dual overhead cam V8 Northstar and its derivatives, drew heavily from the LT5's design and lessons learned from its production.[30] GM also took lessons learned from producing a completely aluminum engine and applied them to the new LS series of engines.

The LT5 was available on the following vehicles:
1990-1995 Chevrolet Corvette C4 ZR-1 equipped with 6-speed manual transmission (Production: 6,939). Although the LT5 was never used in another production GM vehicle, it did make its way into several Corvette concepts, race cars and even into a limited run of the Lotus Elise GT1.