1. Identify the Engine Family:
* The most common engine in 1991 Camaros was the 3.1L V6 (codename "L62"). Look for "3.1" or "L62" cast into the block.
* The "Iron Duke" 2.5L 4-cylinder (codename "LD5") was also offered. You'll see "2.5" or "LD5" on the block.
* The "305" 5.0L V8 (codenames "L03," "L05," and "LO3") was a popular option. Look for "305" or the corresponding code.
* The "350" 5.7L V8 (codenames "TBI" and "TPI") was the top-of-the-line engine. Look for "350" or the "TBI/TPI" designation.
2. Check the Intake Manifold:
* 3.1L V6 (L62): Single-plane intake manifold with a throttle body on top.
* 2.5L 4-cylinder (LD5): Single-plane intake manifold, similar to the V6 but with smaller openings.
* 305 V8 (L03, L05, LO3):
* TBI (Throttle Body Injection): Single-plane intake manifold with a large throttle body.
* TPI (Tuned Port Injection): Dual-plane intake manifold with a throttle body between the two plenums.
* 350 V8 (TBI, TPI): Same intake manifold configurations as the 305 V8.
3. Look for Engine Codes:
* Engine codes are usually found on the front passenger side of the engine block.
* The engine code will provide the most accurate identification.
* Use an online engine code decoder to find specific details.
4. Observe Other Engine Features:
* Cylinder heads: Look for the casting numbers on the heads to help identify the engine.
* Exhaust manifolds: V6 and 4-cylinder engines have different exhaust manifolds than V8s.
* Fuel injection system: TBI has a single throttle body, while TPI has a dual-plane intake manifold with a throttle body between the plenums.
5. Research Specific Models:
* Consult your 1991 Camaro's owner's manual or a service manual. They will list the available engines and their codes for your specific model.
* Online resources: Websites like Camaro forums and parts catalogs can help you identify specific engine variations.
Additional Tips:
* Take pictures of the engine and its components. This will help you compare them with online resources.
* Be aware of potential engine swaps. Camaro owners often swap engines, so the engine may not be original.
* If you're unsure, consult a mechanic for a professional diagnosis.
By using these tips, you can effectively tell the difference between 1991 Camaro engines.
