Have you guys ever heard of a spark plug being blown out of a head?

Discussion in 'SN95 4.6L Mustang Tech' started by jayssilver4.6, Jan 10, 2006.

  1. Well, I took my car in to have the intake replaced, and they found that the number 3 spark plug was blown out of the head.:bang: The service guy said it took threads and all, but I forgot to ask him if there was any other obvious damage. He told me that Fords suggestion is to replace the head at a cool $3300.:nonono: Do you guys think I could tap the hloe put in some new threads(those things that look like a slinky) and it be ok, any advice would be great.:shrug:
  2. Sadly, spark plug blow out is a well known problem here...

    There is a way to repair the threads.

    Sorry to hear that happened to your Mustang man.

    In the future be sure to monitor spark plug torque and ensure that it is within spec. Do not assume any other mechanic has done it, it is necessary to follow up a few days later and re-check spark plug torque to be absolutely sure that it is correct. While you are in there be sure and clean and condition the rubber on the COP rubber boots.
  3. Yeah it happens a lot where I work with our Ford Superduty trucks. They have a tool that bores out the old plug hole and taps it for an over sized plug....works fine.

    3300 is a lot of money for a head, I'd definetly take my business somewhere else if you decide to go that route, unless the cars still under warrenty ?
  4. Helicoiling the head. Yes it's done a bunch.
    Or just buy some ported heads outright. :D
  5. Damn it, its time Ford did something about this instead of avoiding the problem. i dont care if replacing all the 2V heads with new ones does bankrupt them. do it right the first time, make a reliable quality product, and you wont have these problems.

    sorry to hear man, but you arent alone.
  6. http://www.bullittarchive.com/1021.htm


    ©2005 BULLITT Archive
    Spark Plug Blow Out

    No, not Spark Plugs on sale cheap but instead the condition where the Spark Plug Blows Out of the head.

    Seems there have been quit a few 4.6 and 5.4 mod motor owners discovering their spark plug has decided to back out. It appears that once the plug is loose then the cylinder compression starts to force the plug up on the compression stroke and then the COP pushes it back down. It does not take long untill the steel plug has removed all the threads from the soft aluminum head.

    Ford is quick to determine that it is the owners fault for not putting the plugs in corretly and repairs have been very costly to install a new head. Ford says you can NOT repair the head and it must be replaced. As you can imagine a lot of owners are very upset at this situation especially if they have not changed the spark plugs. I have seen posts in other forums where it happened with vehicles with OEM plugs with 10,000 miles up to 75,000 miles.

    You could say that owners are incorrectly torquing down the plugs or over torquing the plug and weakening the threads on the heads. But that does not explain the failures with factory installed plugs.

    Your options

    1. See if Ford will replace the head under warranty.

    2. You can replace the head

    3. Or you can repair the head

    Clearly door #1 is the best, as long as you don't mind Ford tearing your head off.

    #2 is a sure fix but who has the extra money?

    Which brings us to #3. In the old days you could have taken the head off and installed what they call a helicoil. Basically you would drill the old threads out and then cut new larger threads into the head. Next you would turn in a new set of steal threads into the over size threads you just cut. This would bring the size back to the original spark plug size.

    But there is a new product that from what I can tell, (No I have not had to use it, thankfully) people have been VERY happy with the results. It is a product called Big Sert. Also from what I can tell they are doing the repair with out removing the head.

    Basically it is a one piece insert like a bushing. You drill and tap new threads in the head and then screw in a one piece insert. Once the insert is in place the inside of the bottom threads are smaller that the upper threads. This way when you run the supplied driver all the way in you are pushing the sides of the insert into the aluminum head. Locking the insert in to place and forming the last couple of threads.

    Here is a link to the company http://www.timesert.com
    Here is a link to a step by step repair http://www.timesert.com/bigsert-repair.html

    They make a kit just for the Ford 4.6 and 5.4 mod motors. I would call them to make sure you get everything you need. After the repair you remove and replace your spark plugs as you normally would.

    Some people have also ordered the complete kit and then had a local repair shop do the repair. This still saved them 100's of dollars.
    If any one has a picture of a damaged plug or sparkplug hole could you send it to me to post as an example. Thanks

    So what can be done to prevent this from happening to you? Well it is either because the plug was over torqued and started pulling the threads out of the aluminum head or the plugs were not installed tight enough and begin to back out.

    Torque for the Mustang GT is 7-15 foot pounds. Or 1/16 th of a turn after the plug is finger tight. I have experimented using anti-seize compound on the threads only, not on the tapered shoulder and set the torque wrench to 13 lbs. With this setup the clicker torque wrench breaks right at 1/16 th of a turn. I have been checking the plugs every 10,000 and so far they have not loosened.
    ©2005 BULLITT Archive
  7. I really dont like the idea of drilling and tapping the head while on the engine. That means aluminum shavings are going into the cylinder. And that cant be good...
  8. :stupid:
    Just pull the COP off, and drive a 7cylinder for awhile. Can't believe 3300 for a new head?!?! You could get Patriot Stage III's for that, and new cams, and a full tank of gas.

  9. You could get Patriot Stage III's for that, and new cams, and a full tank of gas.

    That would be my choice.... that's why i have a $10k limit on my credit card!
  10. ******* ford for ya...jesus.

    Either way, they should replace the thing for ya, hell they got the money. Did you replace your plugs or are they stock from the factory...if they are stock i'd get a lawyer and tell them your going to be suing them....i bet they'll act then.

    IF you changed them yourself, right away they say it's your fault. BULL..... ANY normal guy would snug it up and tighten it till she's tight...the wouldn't leave it loose like a retard, it's the aluminum threads which are only 1/32nd of an inch big and their are like what 3 or 4 threads.

    THIS did happen to me, do a user search on my name and you'll see the post i had up in mid novembor. I have a 4.6 95 thunderbird and i couldn't believe it when it actually happened..... I got REALLY lucky though, it didn't take any threads except the last one-i was able to firm down a new plug and that's it. But i'm sure one day i'll be doing 70mph and it'll blow out on the highway.

    Can't wait....this will be the time i'll set my own car on fire.
  11. Or save up for a better head....
  12. Thanks for the info and links Kilgore Trout. I added this thread to the Tech Sticky at the top of this forum.
  13. Happened to me, TWICE.

    Once, under the factory 3 year warranty. Ford replaced the passenger side head under warranty. Thank god I had a Motorcraft plug in there.

    Second time, under the 7 year extended warranty. Ford replaced the driver side head, again under warranty. Thank god I bought the extended warranty, as it would've cost me over 2 grand. Motorcraft plugs in there again woot.

    3300.00 is outrageous. Go elsewhere if you have to pay out of pocket.

    BTW, there is a TSB (I believe) for this problem (I may be wrong). If you're still under warranty, inquire about this. Hope you got Motorcraft plugs in there.

    Good luck.
  14. The early V10 heads had this problem and when I purchased my RV with the V10 that was the first thing I asked the Technician and they said it was fixed in 2002. What changed torque requirements. I visit all the RV web sites and nobody seems to have the problem after 2003.
  15. From what I have seen, it is caused from people using the wrong threaded spark plug. A lot of these issues have came from the 5.4l SOHC engines.

    Correct threads
  16. Take it to a speedshop that does head work. Even if they replace the head, it won't be anywhere near $3300.00
  17. I've yet to see this happen on a 2v application, luckily for me.

    I have seen two 4v engines (Cobras) do this. One '99 and one '01. One is a good friend of mine who traded his shortly after for a black '04 Terminator; the other is a member of my local Mustang club and still has his car today.

    Oddly enough, they both blew out #3.
  18. Just like everyone else said it's happened to many before.

    There is a better option to possibly reduce the likelyhood of blowouts for those of you who are still with factory half length thread sparkplugs from Motorcraft.

    FoMoCo changed the recommended plug for the Bullitt 4.6 recently, the new plug has full length threads (roughly 20% more seating area). The Motorcraft p/n is AGSF-32PM.

    The info is in Bullitt Archives here:http://www.bullittarchive.com/1021.htm

    I'm gonna change my plugs this spring when I get mine out of storage to the new ones.
  19. it happens to crown vics a lot as well.
  20. Has this happened to anyone with original Factory installed plugs? What should the torque be on the plugs? Should everyone check their plugs periodically? If so, how often? Thanks for the tip re: the longer thread plugs!