Im am looking into some different spark plugs for my car, and I need to know what the stock heat range is of the plugs. If anyone could help me on this, it would greatly be appreciated.

Brian

 

For the 95 LT1 the stock AC is R45LTSP. The "45" is the heat range.

 

Thanks for the help. So i take it the TR55's are a heat range of "55", is this correct??

Brian

 

Yes that is it. But I'm not sure that you can say an AC with a heat range of 45 is going to be the same as an autolite with a heat range of 45. Different manufacturers # don't necessarily correspond with each other. Also note the the stock AC type is of the long tip design to move the tip closer to the cumbustion chamber. This will affect heat dissipation also. When you select a new plug you should start with the specific recomendation from the manufacturer for your specific engine. It's best to try their recommended plug then check the plug condition and select a different one if needed based on the condition of that plug after some use. Within a specific manufacturer line you can go up or down numerically to pick a different heat range but again I don't think you can jump across manufacturer lines for the heat range.