* Compression Ratio: Higher compression ratios require a colder heat range plug to prevent pre-ignition. Lower compression ratios can use a hotter plug. This is the most crucial factor. What's the static compression ratio of your engine?
* Driving Style: Aggressive driving (high RPM, hard acceleration) generates more heat and requires a colder plug. More leisurely driving can tolerate a hotter plug.
* Altitude: Higher altitudes require colder plugs due to less dense air.
* Accel Ignition System Specifics: While Accel makes quality systems, some models might have slightly different energy output. Consulting Accel's recommendations for your specific system would be beneficial. However, this information is usually linked to the heat range and not the specific type of plug.
* Fuel Type: You mention "straight gas," but specifying the octane rating (e.g., 87, 91, 93) helps determine the ideal heat range.
Finding the Right Plug:
Instead of guessing, the best approach is to:
1. Consult your engine's specifications: Look up the recommended spark plug heat range in your engine's owner's manual (if you have it) or a reputable engine parts catalog. This should give you a starting point.
2. Check the existing plugs: If you've already got plugs in the engine, carefully inspect their heat range markings (usually on the insulator). This shows you what's currently installed and might indicate a working baseline. Look for signs of fouling (too cold) or burning (too hot).
3. Consult Accel's recommendations: Check Accel's website or documentation for their spark plug recommendations, considering your specific ignition system. They may have a guide for selecting the correct heat range.
4. Use a reputable parts supplier: When purchasing, consult with a knowledgeable parts counter person at a reputable auto parts store (e.g., NAPA, AutoZone, etc.). Give them all the details mentioned above (engine specs, ignition system, driving style, fuel type, altitude). They should be able to help you select the correct heat range and type.
General Guidelines (But Not a Substitute for Proper Research): A common starting point for a 350 Chevy is a range of around #6 or #7. However, this is extremely general, and deviating from this based on the factors above is likely necessary. A hotter plug is denoted by a lower number (e.g., #6 is hotter than #8).
Plug Type: NGK, Champion, and Autolite are all reputable brands that offer a wide range of plugs suitable for your application. The type (copper, platinum, iridium) is less important than getting the *correct heat range*. Platinum and iridium plugs generally offer a longer lifespan.
In short: Don't rely on generalized advice. Do your research and consult with experts to avoid engine damage from using the wrong heat range. Getting the right heat range is far more important than the specific brand or type of plug.
