Corvette: Year by Year

1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964
1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976
1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024

Corvette ZR-1

Part Two

Although there was a lot differentiating a Corvette with the ZR-1 option from its contemporaries, there is no doubt that the main event was under the hood. After the turbo engines were out of the running, multiple overhead cams with four valves per cylinder was the configuration given the nod. Group Lotus in Hethel, England was awarded the task of engineering the effort. Lotus had an excellent track record engineering exotic engines and the fact that they had recently been purchased by GM probably didn't hurt them either. Originally the plan was to adapt the standard small block to accommodate overhead camshaft four valve heads. But a snag developed early in the R&D process when it was discovered that engine would not fit between the uniframe rails, a necessity for production at the Bowling Green plant.

The solution: give the ZR-1 its own block. That block would accommodate the production requirements, but there was an economic downside. The new block would mean the ZR-1 would cost a lot more to develop and build and this would have consequences for the future of the ZR-1.

In addition to hiring Group Lotus to develop the engine, GM made one other smart move and that was have Mercury Marine in Stillwater OK manufacture the powerplant. With a production schedule of only about 18 motors a day, the small marine motor manufacturer with an excellent quality record was the ideal candidate.

ZR-1 motor statistics:

Designation: LT5
Configuration: V8, 350 cu. in., four overhead camshafts, four valves per cylinder
Intake: Multi-port fuel injection
Compression Ratio: 11.0:1
Horsepower: 375 @ 5800 RPM (1990 to 1992)
405 hp @ 5800 RPM (1993 to 1995)
Torque: 370 lb-ft @ 4800 RPM (1990 to 1992)
385 lb-ft @ 5200 RPM (1993 to 1995)
Bore/Stroke: 3.90" (99 mm.) x 3.66" (93 mm.)
Block: Aluminum; Nickasil coated cylinder liners
Heads: Aluminum, cross flow

Click here for ZR-1 C4 Corvette slideshow

Right: A novel feature of the ZR-1 was the power key which quickly earned the nickname "valet key". There were two modes: "normal" and "power". Power mode featured all 375 hp while the normal status, which worked by disabling the secondary intake ports, limited the output to about 200 hp. The system was set up to reset to normal each time the main ignition was turned off.

It's Still Hard to Believe!

These sights were - and still are - mind blowing to Corvette enthusiasts. Four overhead camshafts pushing on four valves per cylinder is a concept that even today has Corvette fans shaking their heads in amazement.