Recently purchased 1999 f350 with 5.4 v8 with a MagnaCharger SC kit installed by prior owner. The current plugs are Motorcraft AGSF22WM (SP-479) platinum plugs gapped at .054".

It is only running 6lbs of boost. Are NGK TR-55's (NGK 3951) or TR-6's (NGK 4177) the ones i need and if so how tight of a gap? I don' t want to spend the money on iridium plugs.

curtis

 

I installed the TR-55's gapped at .040" and it seems to like them. It also helped that I replaced a bad plug boot on #7. It idles fine and the slight hesitation at part throttle load is gone.

I must say, what a PITA to do the plugs.

curtis

 

.035-.038 is good for 6-7lbs