I had the car tuned with the autolite 103s in but decided to switch to the stock heat range plug .. I drove the car for 30 miles or so with a few wot runs and pulled one of the plugs and it was yellowish white and the diode was not flat at the top. Would adding more fuel through the computer solve this or is it better to run a colder heat range plug with heads and cam car ? does anybody know how much colder than stock 103s are? My ignition is a msd digitil 6 with jacobs ultra coil on a 95 lt1 .. thanks

 

Spark plugs will not change air fuel mixture.

What you are most likely seeing is that the hotter plug burnt off the deposits making the plug appear lean. Plugs are read for color on the inside near where the insulator meets the side body of the plug. The ground electrode can be used to determine the temperature. The electrode color can vary due to fuel type. Sometimes they are tan, red or green depending on fuel additives. White is generally indicating too hot & a blue discoloration of the metal or rounded tips generally mean too much heat either from lean mixtures or too hot of a plug. I would think 2 ranges colder than stock should be OK. What are you running that you call "stock" heat range? Often the plug heat range cross reference leaves a lot to be desired.

 

thanks for answering my post the plugs that were in the car are champion RS14YC6 they are suppose to be stock heat range LPE stated. So you feel 103s will be fine . I know the champions wont work.