[RACINJASON22]

noahdallas from what I have come across most books will tell you .045 for HEI, but this is misleading because the plug manufatuer actually determines the plug gap. Let me explain the OEM for you engine may be .045 for 75 chevy 350 with say AC R44t spark plug BTW that is the correct number for you, Then say since you want a better plug you go to a AC R44tx same thread, same reach, same taper, plug gap now .060 all because of the plug design. The main thing you have to be concerned with is getting the right thread size, reach, and taper if needed from your parts store wich can be tricky on rebuilt engines (ex. heads not off of original engine and vise versa.) SO that being said plug gap depends on what plug your parts guy gave you, and by no means don't trust all the counter guys at your local part stores.