* L48 350 CID (5.7L) small-block V8: This was the most common engine. The timing specifications for this engine will be found in the owner's manual or a Chevrolet service manual for that year and model. They'll specify initial timing and total timing at various RPMs. Expect to see initial timing in the range of 6-10 degrees BTDC (Before Top Dead Center), but the exact number needs to be verified in the manual. Total timing (after the centrifugal and vacuum advance are fully engaged) will be considerably higher, usually in the 30-40 degree range.
* L81 350 CID (5.7L) small-block V8: This was a higher-performance version of the 350. Its timing specifications will also differ from the L48 and again will need to be found in a service manual specific to that engine. The higher performance engine might have slightly more aggressive timing.
* Crossfire Injection: Some 1981 Corvettes used a fuel injection system known as "Crossfire Injection" This significantly alters timing control. The timing will be computer controlled, and the specifications will be in the form of sensor and computer settings, rather than a simple degree advance. You would not adjust timing directly but work with the computer's parameters through diagnostic equipment.
To find the correct timing specs:
1. Locate your engine code: This is usually stamped on a pad on the engine block. This code (like L48 or L81) is crucial for finding the correct specifications.
2. Consult a service manual: A Haynes or Chilton repair manual for a 1981 Corvette will provide the detailed timing specifications for your specific engine. A factory service manual is even better as it will have the most accurate information.
3. Use a timing light: To check your current timing, you'll need a timing light. This tool will allow you to see the timing markings on the harmonic balancer while the engine is running, and compare it to the specifications you find in your manual.
Do not attempt to adjust the timing without a proper understanding of how your vehicle's ignition system functions and the necessary safety precautions. Incorrect timing can damage the engine.
