ok so the stock gap on the 289 for 67 is what? like .35 right? well since i have GT40P heads and use different plugs i should set em to the stock gap for the explorer right? which is .54 or no? someone suggested i gap em to .45 or so but i'm confused.

 

ford changed the gap when they introduced the duraspark ignition system, much more accurate and higher power going to the plugs. old points systems are 35 give or take. durasparks are usually around 45 to 50. if your using points yet id say stick with the 35. if your using a high energy ignition system then you can open the plugs up to 45 to 50, it just takes more current for current to jump the gap hence points with lower voltage needed a smaller gap. id say stick with whatever ignition system your using. this has always worked for me, just my opinion.