Which Spark Plug to Use?

[Vin Man]

I'm building a new 200 with an Aussion head and HEI/DUI distributor. Which spark plugs should I purchase?

 

[mustangsilly]

As far as brand, they all work. I use Autolites one step colder than what is called for. Do you have an HEI distributor? What is your compression? What octane fuel are you using? How far advanced is your ignition timing? All those will affect spark plug performance. I would start with the colder stock plugs and run them for 100 miles or so and then pull them and read the core nose (porcelain insulator). If its black, go to a hotter plug. If it's rust color, its about right, if the electrodes are melting, it's too hot.

 

[Vin Man]

As far as brand, they all work. I use Autolites one step colder than what is called for. Do you have an HEI distributor? What is your compression? What octane fuel are you using? How far advanced is your ignition timing? All those will affect spark plug performance. I would start with the colder stock plugs and run them for 100 miles or so and then pull them and read the core nose (porcelain insulator). If its black, go to a hotter plug. If it's rust color, its about right, if the electrodes are melting, it's too hot.

Thanks for the input. Yes, HEI distributor. 87 Octane. I don't remember the compression ratio, but it wasn't too high.

 

[wallaka]

NGK IRIDIUM IX WR51X stock #7510.

The NGK plug is the latest in technology, it has a pin center electrode which requires less voltage to fire & the center electrode is iridium which will last 100,000 miles in a engine in good shape.

I concur with Bill's assessment. NGK Iridiums are the best plugs around.