Spark plug blew out - Team Camaro Tech
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post #1 of 13 (permalink) Old Jul 10th, 09, 02:42 PM Thread Starter
MM
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Spark plug blew out

So I'm going for a little drive today and I'm about half a mile from the house and suddenly the engine starts making this god awful loud noise. I though my header cracked or a bolt holfing the header on came out so I slowly turned around and drove home. Upon closer inspection, I see that one of the spark plugs has fallen out still attached to the wire. My question is, could I have damaged the engine/valves/etc from driving with the spark plug out for about a half mile? I assume I have stripped threads but am waiting for things to cool down at the moment.

Thanks!
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post #2 of 13 (permalink) Old Jul 10th, 09, 02:44 PM
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Re: Spark plug blew out

Probally didnt hurt anything if thats all you drove it..the plug probally backed out..over time they will loosen up if they are not that tight!! Check the threads good when it cools down, maybe run a cleaner threw the threads..dont assume the worse!!
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post #3 of 13 (permalink) Old Jul 10th, 09, 02:45 PM
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Re: Spark plug blew out

Had this on a 68 Buick GS. No harm done.

'67 rs - ordered new by my Grandfather
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post #4 of 13 (permalink) Old Jul 10th, 09, 03:07 PM Thread Starter
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Re: Spark plug blew out

Thanks guys! That makes me feel a little better except now I realize I'm an idiot because I just went out and checked and there are 4 other plugs that are in various stages of looseness. Man, I need to pay closer attention to my baby. Weird thing about the plug that came out is it appears to be damaged because the ceramic center rotates within the metal thread/nut assembly. I was thinking, wow is this some kind of new plug or what? You see I just bought the car a little over a year ago and havent pulled the plugs (or tightened them obviously). I guess its a good time to replace the plugs and take a look at them--maybe even do a comp. test while I'm at it. The plugs are acdelco R44TX, btw.

Thx
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post #5 of 13 (permalink) Old Jul 10th, 09, 03:56 PM
 
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Re: Spark plug blew out

No, stop at 2 beers tuning her up!

pdq67



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post #6 of 13 (permalink) Old Jul 10th, 09, 04:05 PM
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Re: Spark plug blew out

Man thats an easy fix, your lucky that its not stripped threads and all is good. I agree stop at the 2-beers for tunning.

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post #7 of 13 (permalink) Old Jul 10th, 09, 04:07 PM
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Re: Spark plug blew out

Remember that gasketed plugs need more torque than the taper-seat style. Taper-seats don't need much at all to stay tight.
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post #8 of 13 (permalink) Old Jul 10th, 09, 05:00 PM Thread Starter
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Re: Spark plug blew out

Now that you mention it, what is the proper torque setting for a spark plug?

And thanks for the advice on how many beers required for proper tuning!!

Mark
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post #9 of 13 (permalink) Old Jul 10th, 09, 10:20 PM
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Re: Spark plug blew out

Interesting that they were AC Delco plugs. I've seen this twice myself and both times they were AC Delco plugs. Once was on my Beretta GT I had back in the early 90s and another time on my boat. The boat only had 25 hours on it when the plug failed and the Beretta had probably 30,000 miles on the plugs when one failed. It is an awful noise when they fail this way.

Wonder if anyone has seen this on plugs other than AC?

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post #10 of 13 (permalink) Old Jul 11th, 09, 07:57 AM Thread Starter
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Re: Spark plug blew out

Dave,

When I went to the auto parts store to get new plugs, the kid at the counter said "that's weird, this is the second time today that I've seen a plug fail that way". The other plug he saw wasnt an acdelco (didnt say what though or I dont recall now) and it was out of a car with a supercharged 5.4l engine. My friend wondered if maybe the plug broke (to where the center would spin) from when it got slammed out of the engine, possibly hitting something to cause that.

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post #11 of 13 (permalink) Old Jul 11th, 09, 08:23 AM
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Re: Spark plug blew out

The 4.6 and 5.4 Ford engines are notorious for that. In fact, Snap On makes a tool specifically for this. It's a heli coil kit, but nothing like the ones in the stores. It is a seriously heavy duty heli coil. I MEAN HEAVY DUTY!!!! Hopefully all it did was loosen up and back itself out.

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post #12 of 13 (permalink) Old Jul 11th, 09, 03:32 PM
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Re: Spark plug blew out

Quote:
Originally Posted by MM View Post

the ceramic center rotates within the metal thread/nut assembly.
doesn't matter what brand, this is a symptom of extreme overtightening.Which doesn't fit with the plugs unscrewing from the heads, but that's what loose ceramic is caused by(overtight). Wish I could draw you a cocktail napkin diagram but here's how it would read,,,, a plug is held together by "crimping" If you look at the metal hex from the side you can see a slight barrel face or ridge in the part right below the hex. This is where they criimp or crunch or contract the housing to cause it to SHORTEN. It needs shortened in order to seal off the internal gaskets plural.
When the hex gets overtightened it will twist this built in weak spot in the metal shell, loosening the crimp, crush, whatever you want to call it.

Edit: a long time ago I remember a bunch of Champion industrial plugs had a recall due to bad crimping procedures. You'll never hear that for dollar 2.99 automotive stuff though. I've also seen big engines blow the center out of plugs from heat and detonation, and keep running. Talk about scary to walk up onto.

Plugs on my junk torque to 50#', but they are bigger. I imagine 25 would be about right on cars. I never put a torque wrench on car plugs, just calibrated forearm. Taper seat tightens to 1/8 round after contact which sometimes feels too tight to me and I stop before then. I torque industrial plugs, they cost 100$ a pop and on a V-16 that hurts.

Tim Smith

Last edited by 77wolf10.85; Jul 11th, 09 at 04:19 PM.
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post #13 of 13 (permalink) Old Jul 11th, 09, 10:18 PM
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Re: Spark plug blew out

Well what Tim is explaining is exactly what I've seen. The ceramic coming loose from the crimp, and you could see the staining from the combustion chamber leaking by at the joint. On the boat I suppose the previous owner may have had the plugs out when they winterized it one year. But on the Beretta I bought it new. Since I work almost exclusively with 1/4 drive on the aircraft I carry that over at home on the cars, unless it's heavy work where something larger is needed. I don't think I over torqued this plug, it was on the back side near the firewall, but who knows, it's possible if it doesn't take too much over tightening to cause this type damage. But it sounds like this isn't all that uncommon to find on AC plugs these days.

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