* Distributor is not fully seated: The distributor shaft needs to be fully seated in the engine block. Even a slight misalignment can throw off the rotor's position significantly. Make sure it's pushed down firmly and rotates freely.
* Incorrect timing chain/gear alignment: If the timing chain or gears are off, even slightly, the engine's rotational position relative to the distributor will be incorrect. This is a major cause of misalignment and requires checking and correcting the timing chain/gears.
* Distributor gear is damaged or worn: A damaged or worn distributor gear won't mesh correctly with the camshaft gear, leading to inaccurate rotor positioning.
* Distributor is the wrong one: You might have accidentally installed the wrong distributor for your engine. Distributors are not interchangeable between different small-block Chevy variations (e.g., different years, different ignition systems).
* Rotor is installed incorrectly: While less likely, ensure the rotor is correctly seated on the distributor shaft and that it's not somehow binding.
* Ignition timing is significantly advanced or retarded: If someone previously significantly altered the ignition timing, getting it back to the correct position may be more difficult than usual.
* Engine rotation: You need to make sure you're turning the engine in the correct direction (clockwise when viewed from the front of the vehicle). Turning it backwards can easily lead to confusion.
Troubleshooting Steps:
1. Verify Timing Chain/Gear Alignment: This is the most crucial step. Use a timing light or a degree wheel to ensure the number one piston is at top dead center (TDC) on the compression stroke. Then, make sure your timing marks on the crankshaft and camshaft align correctly.
2. Double-check Distributor Seating: Remove the distributor and inspect both the distributor shaft and the distributor hole in the block for any damage or debris. Make sure it goes in smoothly and sits flush.
3. Inspect Distributor Gear: Check the distributor gear and camshaft gear for wear or damage. Replace either if necessary.
4. Verify the Distributor is Correct: Confirm you have the right distributor for your specific engine.
5. Carefully Reinstall the Distributor: Once everything is confirmed, reinstall slowly and carefully.
If you've checked all of these and are still having problems, it's best to consult a mechanic experienced with small-block Chevy engines. Getting the timing wrong can cause significant engine damage.
