i have a 2007 screw f150 with the flex fuel 5.4. this is my work truck and i tow a lot with it. i have just over 60k on it and would like to change the plugs on it. my local autozone doesnt have the motorcraft sp507 plugs but they do have the NGK platinums part# 3403 and the NGK iridiums part# 7164.

which ones would be best for my application?

are the stock plugs iridium or platinum?

thank you for whatever help you can give me.

 

None of the NGK's will work with the 2 piece plug heads.

Make sure you follow the latest plug change TSB. And you'll need to get the broken plug removal tool. These plugs break off in the heads very often.

Rockauto.com will probably your best bet for the Motorcrafts at a low price.

 

i just went to rockauto.com and they dont have motorcraft spark plugs for my application (2007 4wd 5.4 flex fuel)

 

If you go to motorcraft.com, you can enter your vin and it will give you part numbers for everything that will fit your truck. There are two separate part numbers for each of the plugs, you may need to search both, try those in the actual part number search at rockauto.

 

Is it missfiring? If not i wouldnt change them yet. 60k miles isnt much. Maybe at $100k. Whether you are pulling or not pulling alot, that spark plug sparks the same either way. So you are not working that spark plug anymore when you are pulling than when you arent pulling. It isnt like your motor oil and transmission oil, those two can be effected by pulling more with your truck. JMO.

 

Whatever you do..DO NOT wait untill 100,000 Miles to change your plugs. Save yourself aot of potential headache and change them now.

 

^x2. Are the new motorcraft ones a single-piece design? I've heard it both ways

 

Plugs are still 2 piece, just a different heat. Ford changed the heads to allow for a different one piece plug in 08.

 

So even though they are 2piece, we won't have the problem with them seizing and ing up our heads?

 

They don't seize. Carbon builds up on the shafts past the threads and shears off the firing end of the plugs when you go to crank them out.