KOBRA2848 Posted February 25, 2013 Report Share Posted February 25, 2013 I decided it was time to change the spark plugs on my 2008 Shelby GT. I was concerned because all of the horror stories I have heard about the plugs breaking. I decided to go with the replacement Motorcraft plugs. I turned all the plugs about an 1/8 turn and sprayed Chemtool B12 and let sit about 15 minutes. I'm happy to say all eight came out in one piece. They did have some carbon build-up which the B12 softened nicely. I also changed out the fuel filter and swapped the tranny fluid to Mobile One. Next up is to put on the KR mufflers. My car has right at 29,000 miles and lives on Shell premium since I got it. All in all I would say it went smoothly. Mark Link to comment Share on other sites More sharing options...
ilmor Posted February 25, 2013 Report Share Posted February 25, 2013 Glad to hear it all went well! Eventually I'm going to entrust that spark plug job to my dealer!! I'll eventually change mine due to "years" on the car, not "miles". I guess I should check my manual to see what's recommended.... Edit - Wow, just checked the manual - spark plugs should be replaced at 100,000 miles!! - no "years" mentioned. Maybe I'll just plan to replace them at 10 years...along with the tires and whatever else is needed. Link to comment Share on other sites More sharing options...
KOBRA2848 Posted February 25, 2013 Author Report Share Posted February 25, 2013 I actually spent more time researching than it took to change them. I noticed the new plug had a different part number than the original factory plugs. They appeared identical but was told the shell is made of a different material. I wouldn't hesitate to do it again but would be leary to go past 30,000 miles without changing. I don't see how you would be able to remove them at 100,000 miles. Mark Link to comment Share on other sites More sharing options...
AstroDan Posted February 28, 2013 Report Share Posted February 28, 2013 Well... I'll be dead before Betsy has 100,00 miles, so... Link to comment Share on other sites More sharing options...
young768 Posted February 28, 2013 Report Share Posted February 28, 2013 2008 and newer cars used the new 12mm spark plugs which I do not think had the breaking problem that the older 16mm plugs had. Link to comment Share on other sites More sharing options...
KOBRA2848 Posted February 28, 2013 Author Report Share Posted February 28, 2013 My car has the earlier heads with the two piece plugs. I was surprised how much the gap opened up in only 29,000 miles on the factory plugs unless they were gapped wrong when put in. It's my wife's car and she commented that the car seemed to have more power but I also changed out the fuel filter and swapped the factory mufflers to KR's at the same time. Mark Link to comment Share on other sites More sharing options...
old man Posted February 28, 2013 Report Share Posted February 28, 2013 Which new plugs did you use? Part #? Thanks Harley Link to comment Share on other sites More sharing options...
IASHELBYGT Posted February 28, 2013 Report Share Posted February 28, 2013 Which new plugs did you use? Part #? Thanks Harley +1 Link to comment Share on other sites More sharing options...
KOBRA2848 Posted March 1, 2013 Author Report Share Posted March 1, 2013 The plugs I pulled out were the SP-462 (PZT1F) while the replacements were a SP-514 (PZH1F). From what I was told the only difference is the lower ground shield is coated or made out of a different material to help prevent carbon from sticking to it. I purchased my plugs from American Muscle since they were only $69.99 shipped while the cheapest I could find local was around $14 bucks a plug. Thanks Mark Link to comment Share on other sites More sharing options...
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