bent spark plug electrode

[skids]

I noticed a slight miss recently on left bank, and when I pulled plugs I noticed #5 plug electrode was bent, just about touching tip. Well, theres cause to problem. But, why was electrode bent? Any idea? Maybe I accidentally dropped that plug while installing, but that was approximately 2 months ago, and I didn,t notice miss till recently. I have sidepipes so it's easy to hear any unusually firing. Engine is a 68, 327-350.

 

[Mike McKown]

You could have installed it that way. They will run okay for awhile with a closed up gap. Then they will foul. If you have an extended tip plug in there, you may have one of those engines that the piston has tapped it. Only if you have the domed pistons. Look closely at the tip and see if it has any aluminum stuck on it. If it does, you may have big problems. If it doesn't, I'd re-gap the plug, clean it and put it back in the engine and see what happens.

 

[iron cross]

If you are using an extended tip spark plug like {AC R45S} switch to a R45 that does not have the extended tip. Some plugs with the "S" suffix may be too long for some compression ratios and the piston can nick the plug.

 

[Vettefan87]

You could have installed it that way. They will run okay for awhile with a closed up gap. Then they will foul. If you have an extended tip plug in there, you may have one of those engines that the piston has tapped it. Only if you have the domed pistons. Look closely at the tip and see if it has any aluminum stuck on it. If it does, you may have big problems. If it doesn't, I'd re-gap the plug, clean it and put it back in the engine and see what happens.

How do you regap a plug? Is there a tool that you use to do it? Thanks.

Justin

 

[JonM]

How do you regap a plug? Is there a tool that you use to do it? Thanks.

Justin

Justin...you could use one of these, or a set of feeler gages
Their are other types of gages also.

 

[vetteboy86]

I thought those could cause damage to the electrode? If you have a gap that is off by 20 thousandths or so, it would be work to re-gap with one of those. I always thought you could by them gapped to a specific gap.

Craig

 

[Vettefan87]

So if I have a plug that isnt gaped right I have to take it back, and get a new one from the store?

 

[vetteboy86]

Well isn't that what c4c5 told us at the tech seminar.


Craig

 

[Vettehead Mikey]

I thought those could cause damage to the electrode? If you have a gap that is off by 20 thousandths or so, it would be work to re-gap with one of those. I always thought you could by them gapped to a specific gap.

Craig

Spark plugs do not come pre-gapped from the manufacturer. Each plug should be individually verified, and adjusted as required to the recommended gap for your vehicle.

Perhaps somebody was thinking of the bubba aftermarket 'hi performance' plugs, or the non-adjustable iridium or unobtanium type plugs for modern engines. Not applicable to our older engines.

 

[Ron Miller]

I thought those could cause damage to the electrode? If you have a gap that is off by 20 thousandths or so, it would be work to re-gap with one of those. I always thought you could by them gapped to a specific gap.

Craig

Gap them by bending in or out (slightly, of course), the outside ground electrode, not the center electrode. That's what the hole is for in the tool posted above, will slip over the outside ground electrode and "grab" it allowing you to bend it slightly to open up the gap.

By the way, in response to the original post, if you're certain that you didn't accidentally bump the plug when installing it accidentally closing the gap, I would think almost certainly you had mechanical contact by some means to cause the gap to close. They certainly won't close during normal operation.

 

[vettepilot]

The other thing that could have happened at the time of installation, you could have missed setting the gap on that plug. Been known to do that myself. Lost track of which one's were gapped and those that still needed it usually due to some interuption during the process, like wife calling for lunch, dinner.... maybe another cold beer run to the refrigerator.


vettepilot

 

[G Winter]

Have you checked any of the other plugs, if one happened to be hitting the piston they would almost certainly all hit. If none of the others are bent I would say it was installed that way. All plugs should be checked and gapped before you install them. Other than the specialty plugs.

 

[skids]

plug

The engine ran fine for the last two months since I pulled the plugs and checked them. But what I failed to mention is that this misfire I had, seemed to start after I let er rip. Shifted at 6000 out of third.Hummmmmm! That one plug wasn't loaded up either. Looked the same as the others. After two months, If i did accidentially install that plug with closed side electrode, I would for sure of noticed it before now.

 

[vetteboy86]

If the car was getting hotter than designed, could that have caused the damage to the bent electrode. I guess I am trying to describe some type of melt, which leads to a bend effect.


So now spark plugs come a specific gap from the factory. They are all just differen't. That is weird because the set of rapid fires I got was very close to one another in the gap.

Craig

 

[vettepilot]

If the car was getting hotter than designed, could that have caused the damage to the bent electrode. I guess I am trying to describe some type of melt, which leads to a bend effect.


So now spark plugs come a specific gap from the factory. They are all just differen't. That is weird because the set of rapid fires I got was very close to one another in the gap.

Craig

At the time of manufacture, the machine that sets the electrode sets each one approx. the same. However, because of normal manufacturing tolorences, they do have some difference. Additionally, the plugs are designed with more than one application in mind. Therefore the specific ignition system/engine compression ratio/ fuel metering etc. has much to do with the required air gap for each engine/chassis application. Hence the requirement to set the plug gap before installation into the engine.

vettepilot

 

[vetteboy86]

I guess some of us just get lucky, if the plug gap is what we want.

Craig