Crazy plug thread question
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Fleet Mechanic
Joined: Nov 2000
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From: In my House
Crazy plug thread question
Ok I'm sitting here wondering about these thread counts. Is it just the fact that on the pre 03 heads, there is just not enough "head" there to tap out more threads? What I'm asking, Is there not enough material there on the head, is that why they only have 4 or 5 turns of thread in there? Or can we go in and tap more threads into it. I guess its safe to say that the 03-04 heads are thicker in the plug area then.
Just thinking aloud
RIch
Just thinking aloud
RIch
Posting Guru
Joined: Feb 2007
Posts: 2,351
Likes: 8
There's been much said "about these thread counts". However, I've never seen that angle & can see how its a "Crazy" Q. Litigation over FORD's infamous 'Blown Plugs' became a Federal case. You can't seriously believe the solution could be that simple? There'd be Service Bulletins and/or recalls.
Spark plugs are to be tightened carefully to seat & seal, thus reaching as far as they reach. While I did see comments about using alternative plugs w/longer threaded reach, the issue was FORD's change from traditional 'bullet proof' cast iron, to thin aluminum cast heads. A big part of this is related to generations of mechanics accustomed to tightening the snot out of plugs & never consulting torque specs. Apparently thousands of plugs were even overtightened during assembly. Surely many more were overtightened at dealerships, independant shops & by owners. The combination of switching to aluminum, few threads & old habits results in thousands of weakened & fractured threads, allowing the plug to blow out. A loose plug is just as bad, hammering away at aluminum threads of marginal strength until they pop.
Some FORD heads obviously had defects in castings, thread cutting & assembly. The legal fight argues if the design was defective. The 100K mile change interval & debris collecting pit plugs sit in contribute to the problem. After 100K miles 'baked' threads can be damaged just loosening plugs & there's antiseize specs to consider w/aluminum heads. The trapping of grit & corrosives assaults the threads from above.
Spark plugs are to be tightened carefully to seat & seal, thus reaching as far as they reach. While I did see comments about using alternative plugs w/longer threaded reach, the issue was FORD's change from traditional 'bullet proof' cast iron, to thin aluminum cast heads. A big part of this is related to generations of mechanics accustomed to tightening the snot out of plugs & never consulting torque specs. Apparently thousands of plugs were even overtightened during assembly. Surely many more were overtightened at dealerships, independant shops & by owners. The combination of switching to aluminum, few threads & old habits results in thousands of weakened & fractured threads, allowing the plug to blow out. A loose plug is just as bad, hammering away at aluminum threads of marginal strength until they pop.
Some FORD heads obviously had defects in castings, thread cutting & assembly. The legal fight argues if the design was defective. The 100K mile change interval & debris collecting pit plugs sit in contribute to the problem. After 100K miles 'baked' threads can be damaged just loosening plugs & there's antiseize specs to consider w/aluminum heads. The trapping of grit & corrosives assaults the threads from above.
