In 2026, finding an unopened 1991 Chevrolet Corvette ZR-1 LT5 crate engine is like finding a time capsule from the pinnacle of 90s supercar engineering. Designed by Lotus and manufactured by Mercury Marine, this all-aluminum DOHC V12-beater is a masterpiece of complexity and historical significance.

For a collector or restorer, this is no longer just an engine; it is a museum-grade artifact.

1. Technical Profile: The “King of the Hill”

The 1991 LT5 was unique for its high-revving nature and a dual-plenum induction system that essentially gave the engine two personalities.

Listing Details

• 5.7-Liter LT5 V8
• Aluminum Construction
• DOHC, 32-Valve Layout
• Designed by Lotus
• Built by Mercury Marine
• Metal Base w/Table-Top Supports

2. 2026 Market Valuation (Estimated USD)

Price is heavily dependent on whether the engine is still in its original Mercury Marine wooden crate or “loosely” stored.

3. Critical “2026 Status” Maintenance (NOS Warning)

If you are buying a “New” 1991 crate engine today, do not simply bolt it in and fire it up. Rubber and seals do not age well over 35 years:

• Injector Failure: The original 1991 injectors are often ruined by ethanol in modern fuel or have simply seized from sitting. In 2026, the standard fix is a set of FID (Fuel Injector Development) injectors compatible with modern fuel.

• Secondary Actuator Diaphragms: The vacuum-operated secondary butterflies are critical for top-end power. After 30+ years, the rubber diaphragms in the vacuum actuators are almost certainly brittle.

• Secondary Chain Tensioners: The LT5 uses complex timing chains. Even in a crate engine, the plastic guides can become brittle. Most specialists recommend a “look-see” inspection before the first start.

• The “Green” Gaskets: The original paper gaskets used by Mercury Marine are prone to leaking once the engine heat-cycles after decades of dormancy.

4. Parts Availability & Support

By 2026, Chevrolet no longer stocks LT5 parts. Support for this engine is centralized in a few elite specialists:

• Marc Haibeck (Haibeck Automotive): The world’s leading authority on LT5 performance and maintenance.

• Jerry’s LT5 Gaskets: The primary source for the complex, multi-layer gasket sets required to seal the intake plenum.

• Graham Behan: A former Lotus engineer who was instrumental in the LT5 program and still provides consulting and parts support.