BLOWN Spark Plugs / Which Repair ?

Blew a plug out of #4 last week. No warranty because I was " overdriving" my supercharger (2.93 pulley) and did not have OEM plugs (NGK TR-6). I know, I need to find a new dealership (had to go to St.Louis for my "tick" repair). Anyway, they did the Time-sert thread repair and installed a set of OEM Motorcraft plugs. Is this going to hold up at track events this year or is there another new head in my future? What is the best repair? Time-sert, magniflux and rethread or replace the head?

Is that an 03 head with 4 threads or an 04 with 9 threads?

The Timesert is the best repair method for damaged threads in aluminum heads. It has good contact with the head for heat transfer. But some people have said that their plugs run colder since the Timeserts contact the head and plug over a longer length, creating a longer heat transfer path. When I pull my motor (eventually) for better pistons I will either get the newer heads that have 8 sparkplug threads or Timesert all the holes if the new heads are too expensive. I have heard a rumor that ford is going to be making the 2000R heads again. And they flow better stock than our 03-04 heads do after porting. But I bet they will be really expensive.

This was an '03 early build head. Passenger side. I had the "tick" repaired last year (drivers side) and that head has 9 threads. No problems on that side.

That why I check 'em every 3000

Mine loosen up in about that mileage interval. I'm hoping that the new head replacement that SVT just announced will have the 9 thread count. Racing with the helio coil insert doesn't exactly give me a warm fuzzy feeling.

Swapping the head is the best option, but the TimeSert insert kit is by far the most practical and easiest way to fix it.

I had #5 blow out on me several months ago and used the time-sert kit and it's been working great ever since.

Magniflux and rethread?? What is this method of repair?

SlowSVT said:

Is that an 03 head with 4 threads or an 04 with 9 threads?

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There is absolutely no production Cobra in 04 that came with 9 threads in the heads. Zip...nada...zero! This is a common misconception. All 04's came with just the 4 threads. All the tick replacement heads came with just 4 threads. ALL OF THEM!! Until January of 05. That newest head is supposed to have 9 threads. I haven't seen one, but a couple of guys here have had them installed and seen them and counted the threads. THAT IS THE ONLY HEAD WITH 9 THREADS!

You can't count the revolutions of your spark plug to tell how many threads are in the head. Since the plug has 9 threads, it will count that many turns regardless whether you have 2 threads or 20.

FireRed04Vert said:

There is absolutely no production Cobra in 04 that came with 9 threads in the heads. Zip...nada...zero! This is a common misconception. All 04's came with just the 4 threads. All the tick replacement heads came with just 4 threads. ALL OF THEM!! Until January of 05. That newest head is supposed to have 9 threads. I haven't seen one, but a couple of guys here have had them installed and seen them and counted the threads. THAT IS THE ONLY HEAD WITH 9 THREADS!

You can't count the revolutions of your spark plug to tell how many threads are in the head. Since the plug has 9 threads, it will count that many turns regardless whether you have 2 threads or 20.

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I have read many posts stating replacement heads have 9 threads ( pre 1/05 ). i agree that all production heads came with four threads.

What is causing plugs to blow out and strip the threads?

FireRed04Vert said:

There is absolutely no production Cobra in 04 that came with 9 threads in the heads. Zip...nada...zero! This is a common misconception. All 04's came with just the 4 threads. All the tick replacement heads came with just 4 threads. ALL OF THEM!! Until January of 05. That newest head is supposed to have 9 threads. I haven't seen one, but a couple of guys here have had them installed and seen them and counted the threads. THAT IS THE ONLY HEAD WITH 9 THREADS!

You can't count the revolutions of your spark plug to tell how many threads are in the head. Since the plug has 9 threads, it will count that many turns regardless whether you have 2 threads or 20.

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Actually there are 04 Cobra's that came with 9 thread cylinder heads, mine is one of them. I comfirmed it using a fine wire and dragging it across the plug threads. Definately counted 9.

MY DREAM said:

What is causing plugs to blow out and strip the threads?

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They become loose because they are not tightened enough. A lot of the aftermarket spark plugs require more torque then the stock ones. Denso's site recommends 30Nm(Newton Meters) for most of their spark plugs. I've been running mine at that torque for the last 10,000 miles and have not had a problem, they are still nice and tight. I even tightened the stock plugs to 30Nm and ran those for almost 15,000 miles with out a problem. I think Ford's spec is 17 lbs.ft., and 30Nm = 22.5 lbs.ft., so an extra 5.5 lbs.ft. isn't going to hurt the 4 threaded heads and will keep the spark plug tight.

i disagree with your failure assessment.

they dont strip becuase they backed out, they strip becuase they BLEW out.

as it turns out, its plenty common on two valve and sho engines. lightning guys dent the hoods when they pop.

Great I didn't know this.

its a good idea to replace the spark plugs regularly. Maybe every 5,000 miles. I will replace mine soon as my next oil change is done.

ShelbyGuy said:

i disagree with your failure assessment.

they dont strip becuase they backed out, they strip becuase they BLEW out.

as it turns out, its plenty common on two valve and sho engines. lightning guys dent the hoods when they pop.

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Scary, I would not want to be standing over the engine compartment when those bullets shoot out.

on edit: see also my thread regarding the repair i did. magnafluxing is just a way to check for cracks. it doesnt have anything to do with repairing anything.

the lightnings REALLY shoot 'em out. our cars have coil covers to contain the schrapnel.

its apparently VERY common on the 5.4 two valve engine.

and from my correspondence with TimeSert regarding which part # to use:

Hello,
The tooling for the 5553 kit is longer than the tooling
in the 4412E and doing a 4412E repair does not match the exact
OEM hole that was in the head. This means that autolite spark
plugs will not work. You can only use fully threaded sparkplugs.
View the image below and look into your vehicles head you should
see the taper seat then a straight section. We duplicate the spark
plug hole with the 51459 insert supplyed with the 5553 repair kit.

Best Regards,
Time-Sert

Yates...Man said:

Scary, I would not want to be standing over the engine compartment when those bullets shoot out.

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One thing to note- if the plug blows out and spends any more than a second to two whacking the coil pack up against the coil pack cover, consider replacing that coil. The rubber boot will probably be torn and the spring thing inside the boot connecting the coil to the top of the plug will be damaged (stretched).

and L-M dealers stock the coil

ShelbyGuy said:

and L-M dealers stock the coil

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L-M as in Lincoln Mercury dealers??


As you know, I had a spark plug blow out. And now my car is sputtering since the fix. I looked into it and found out the coil was damaged. Do you happen to know the part number for the coil....are they all the same? I can't make out the part numbers on mine. Mine is on the passenger side, second one in from the firewall.

Thanks. :beer: