How to Identify an LT1 Engine

The original LT1 engine, available from 1970 through 1972, was only offered with two vehicles; the Chevrolet Corvette and the Camaro Z28. The LT1 offered increased horsepower and performance at the end of the muscle-car era and their horsepower saw a gradual decrease each year. The engine's short lifespan combined with limited production makes these 350 cubic-inch engines much sought after. Identifying the cylinder head casting number and the engine ID number should allow you to identify an LT1.

Step 1

Locate the ID number cast on the engine block on a machined pad towards the front of the engine. The number is on the passenger side, near the cylinder head and is between seven to eight digits long. Remove the alternator if it blocks access.

Step 2

Decode the LT1 engine ID number. In order, the code identifies assembly plant, month, day, and engine suffix code. When cross-referenced against a Chevrolet listing, the suffix code gives exact engine specifics. As the LT1 was a special edition, high-horsepower engine, a summary of a Chevrolet listing from Nasty Z28 gives the following suffixes for the LT1: 1970-CTC, CTB, CRT, CTR, CTU, 1971- CGY, CGP, CGR, CJK, CGZ and 1972-CKZ, CKY, CKT, CKS, CRS, and CRT. Engine suffix codes matching these identify an original LT1 engine block.

Remove one of the valve covers to access the cylinder head casting number. It is located on the cylinder head, usually towards the center. The casting code will be between six and seven numbers long and needs to be cross-referenced with a Chevrolet listing to verify it as a LT1 Cylinder head. When both component numbers match, it is most likely a genuine LT1 350 c.i.d.


The original LT1 must come from a 1970 to 1972 Corvette or Camaro Z28, however, not all Corvettes and Camaros have LT1 engines. The LT1 term was later used by Chevrolet during the 1990s as the Generation II LT1. Be sure of the year vehicle if the engine is still installed.

Cross referencing various ID and casting numbers contributes to an accurate identification as certain engine components may have been replaced. Because of its unique status, the LT1 was normally kept original.