I just changed my spark plugs today. I had TR6's in my truck and had them in for about 3 years. Well I pulled them today and I checked the gap on them. I usually gap them at .035. Well when I checked them today they were not this gap. They were more like .045. My question is, Does spark plug gap change after you run the spark plug for a long time ? Does the gap widen on the plugs ? When I changed my plugs I had some friends help me put them in and was wondering if they might have gapped them wrong 3 years ago.

Thanks for any help.

 

Plug gaps do wear with miles, but modern plugs are very durable and in street service, probably grow maybe 0.005" per 100,000 miles. How do the electrodes look? if the center one is still quite sharp edged and there's little rounding off of the side electrode, it's likely they went in a little wider than spec. Over the years, the GM specs have been up and down a bunch. As low a 0.025" 5 decades ago, up to 0.080" in the seventies, 0.060" trending to 0.035" more recently... With the added pressure of nitrous, I'd say your 0.035" target was good.

 

I changed the spark plugs to NGK's 3 years ago myself. I had gapped them to .035 but after 3 years it seems the gap got wider. The factory spark plugs were fine.

 

Does anyone else have any other thoughts as to why this happens ?