Just wanted to know if there is any advantage in opening of closing up the gap on my plugs? I heard that doing one or the other can have an affect on gas milage and performance. Does anyone know what gap is optimal? I have them set at what the book recommends. Any advise would be appreciated.

 

I own a '77 4x4 with a 300 six. A friend of mine informed me that I should be using motorcraft plugs. Well that was fine, but I had just put in autolites a week prior, so I wasn't about to change them. The info on my valve cover read the plug gap should be
.050"-.056", so I set them at .055". Tired of crappy performance from my six I decided to put in motorcraft plugs. I went to a Ford dealership and the technician there told me to set them at .048"-.052". I ripped out those !#%@^&# autolites, which are shorteyiiyh;hy

 

I own a '77 4x4 with a 300 six. A friend of mine informed me that I should be using motorcraft plugs. Well that was fine, but I had just put in autolites a week prior, so I wasn't about to change them. The info on my valve cover read the plug gap should be
.050"-.056", so I set them at .055". Tired of crappy performance from my six I decided to put in motorcraft plugs. I went to a Ford dealership and the technician there told me to set them at .048"-.052". I ripped out those !#%@^&# autolites, which are shorter than motorcrafts, gapped the motorcraft at.050" and now she runs 10x better.
I would almost say NEVER run anything but motorcraft in this engine

 

I am usually in favor of greater than stock gaps. If the ignition power is good enough (performance coils, 8.8mm or thicker wires, MSD, etc) then the gap could be wider, which in turn gives more power and better combustion just as long as your stay within manufactured recommended ranges (in this case 0.056 or so). Of course it depends on the spark plugs. I run Splitfires (SF512E) and they work fine, both with wider and narrower gaps. A narrower gap gives better mileage but sacrifices performance (at least in my experience). As for stock Motorcrafts (BSF-44C) the same applies, they're good plugs plus cheap!