today i changed spark plugs on my vt not that the old ones where worn out or anything but its been a number of yrs which i havent changed them so i decided to put fresh ones on, my question is do they need regapping cause i did not do the gap i just put them on as they came factory they are gm genuine plugs so i just put em on like that!
Leave them at 1.5mm for a standard car. Bosch plugs come in at 1.3mm. Try to change them at least once a year. I change mine every 10-15,000k's as i am on LPG.
They should be correctly gapped ex factory, BUT it is wise to check just in case. The NGK plugs have the number 15 at the end of the plug part number, this 15 indicates that the plugs have been factory set to 1.5mm