I was wondering what is a good spark plug to use in the newer vortec heads (906) since i believe that they use lithium plugs would it be alright to run these with my hsr vortec 355 or should i just stick with ac delco rt45s plugs an call it a day also will the lithium plug give a better spark then the ac delco rt45s

 

I'm guessing you mean either iridium or platinum plugs. I'm not aware of anybody making a spark plug with lithium metal as it is very soft, hence it's use in grease. Anyway, any brand with a fine wire electrode in Ir or Pt will be an improvement over the Delcos in longevity if nothing else. While the plugs have some effect on the "quality" of the spark, that is more a function of your ignition system.

 

Look up the part # used in a 98 Chevy truck with a 5.7.

 

I have always believed for gm vehicles, there is no better plug then the manafacture recommended ac delco plugs it came with. If you have added other parts to change the engines performance, I might step up the rapid fire ac delco's, but on a stock engine replace original with the same.

 

lol sorry thats what i meant iridium ill just get the stock plugs for newer chevy trucks an try them out are these plugs shorter also since im running flow tech headers the last stock plugs i couldnt use cause they were rubbing up on the header