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Stuck Spark Plugs
Hi Guys,
Sorry if this has been covered before. I am trying to change the spark plugs on my 351 and two of them are stuck. The engine is a 351w ford motorsport with GT40 aluminum heads. The engine has 4k on it and the plugs are the ones that were already installed when I bought the engine from Summit. So far I've tried spraying the stuck plugs with Liquid Wrench without success. Any help would be appreciated, Roger |
Roger. This is a common problem on older Jaguars, so I've had to free up way too many stuck plugs in aluminum heads. Here is what has worked for me:
-you are correct to try to get a lube into the threads, but I've had to use a heating and cooling process to help this. I like a torch on the surrounding head followed by spraying a freezing liquid on the plug, followed by a liquid wrench or knocker loose kind of product. It's easy to start a fire doing this.... The freezing spray seems to be the key, it's avail at autozone etc. -more drastic is to physically break up the spark plug so that only the steel outer ring remains, then carefully cut a notch that allows it to collapse. I've used grease to try to catch the saw filings, and it's impossible to avoid some thread damage. -most drastic is to have to install a threaded insert. I've done this severel times and it works great, but it seems like it would effect the spark plug operating temperature since the heat transfer path is changed. Good luck. Dave |
Roger;
I would soak the stuck plugs and let them sit overnight. In the morning, put the plug wrench on them and slightly (really, really slightly!!) tighten them. This should break the rust/corrosion without damaging the heads. Reinstall plugs with anti-seize on the treads. Bill |
I've used a cordless impact gun. and PB blaster spray
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Quote:
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Use a 50:50 mix of acetone and auto trans fluid. Just about the best penetrating oil you can find.
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Thanks for all the info.
I'll keep y'all posted |
Well, I've been wondering if plugs really need to be changed a 4k miles.
Perhaps the best thing for me to do is replace the 6 that are not stuck and leave the other two in place. |
No, that would be a mistake! You may never get those plugs out. IMO, the heat/cool cycle with penetrating oil (not WD40) is the best approach and you should do it now before it gets worse. Out of curiosity, did you find antiseize on the plug threads you could get out?
Anyone with an engine with aluminum heads would be wise to pull the plugs when you first receive it and ensure antiseize is on all the plugs. Ford Racing usually only puts oil on the plug threads which can be a problem if the plugs are not changed for years and tens of thousands of miles. |
Another thing to try:
Put the other 6 back in (with antisieze) and run the engine up to full operating temperature. Try to remove the stuck ones with the heads hot. The aluminum heads will expand more than the steel spark plugs. |
Be carefully. Don't change them. Last thing you want is to strip them. Plugs go an easy 35k miles! I would not loosen when hot. You can play but be carefully!
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Hey Mreid .... didn't find any antisieze on the plugs I removed.
Barnsnake. I have put the new plugs in with antizsieze. At this point I'm way out of my comfort zone. I'm going to turn the removal of the two stuck plugs over to a race car engine builder here in town. thanks everyone for the input, Roger |
Good move Roger, but you may still be responsible if he strips the threads. At least he should have some experience and a good technique. Good luck!
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Just for my information, how in the heck do you get an impact wrench into the engine compartment? I can barely get my hands in there.
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Roger----plugs with electronic ignitions and unleaded gas can go 100,000 mile s or more--If the other 6 didn't show any signs of fouling, etc--replace tem with antiseize on the threads and continue to drive ---
Most of the Ford vans with 460 engines had a couple of plugs that never, ever got changed at most shops----- |
Roger:
Should you ever get those two plugs out be sure to torque them to the correct spec. when putting them back in. Most gear heads I know can't tighten stuff enough or use thick enough oil. If the plugs are 14mm torque them to 180 LP-INCHES (15 pound-feet) using a torque wrench (no more). Be sure to use an anti sieze designed for plugs. I bought a torque wrench just for this task. Do not overtighten them! Bob |
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