Hi Guys: I run NGK ZFR-5N plugs in the totally stock 225 six in my 74 Duster. Rebuilt Holley 1945 runs well, air/fuel mixture and idle set to factory specs, timing at 10 degrees before. The engine has 95K miles on it. The plugs seem to foul a bit after about 11000 miles, so I just bought a pneumatic spark plug cleaner from Harbor Freight. It didn't work very well, even when used as directed. Why would a healthy engine foul the plugs this soon? The accompanying photo shows the plugs after 11K miles, with the #1 plug at the top and #6 at the bottom. How do they look to you? Is it easier to just put new plugs in? That's kinda pricey. What do you do to get your plugs squeaky clean before you reinstall them? How long would you normally expect a set of good plugs to last in a slant? Is 11000 miles about when you clean or replace yours? Thanks.
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