Spark Plug

Posted By: DusterKid

Spark Plug - 01/27/15 02:26 AM

I have a mild 360 that I race that is approx 10:1, edelbrock heads and a run a mixture of 1 gal 110 + 3 gal 93 pump gas. 3 or 4 years ago I was putting new plug wires and changed the plugs and notice I had 2 or 3 (I can't remember) plugs that the ground electrode was broke at the bend part. I figured the plugs were old since I didn't remember changing them recently. I just tore the motor down for a freshen up this past month and I had 3 more that were broke. Cylinder 1, 6, 8. I know these plugs are less than 2 years old, so now I"m questioning if I'm running the right plug. The plugs are autolite 3924's. So I guess my question is first off what is causing this? and obviously what do I need to do to fix the issue to prevent this from happening again?

Posted By: Thumperdart

Re: Spark Plug - 01/27/15 04:19 PM

So r u saying they really broke or are they wore out? If they actually broke from contact then that`s a whole nother deal.......

Posted By: MR_P_BODY

Re: Spark Plug - 01/27/15 04:29 PM

If they were burnt off thats one thing.. most times
when they break off they break at the weld point ..
tell us if they are burnt off... lets see a pic..
also if they were hit by the piston they would be
bent down
EDIT
I run that same plug in my street/strip 416 with
10.4 compression.. also make sure you didnt put in
the AR3924... thats the short ground strap for racing

Posted By: DusterKid

Re: Spark Plug - 01/28/15 01:00 AM

I didn't see where they made contact with the piston to bend or brake. The 3 plugs picture were list this, the other 5 were normal. Since all the plugs had the same about of runs on them, if they were worn, wouldn't all of the plugs be about the same or no? Here are a few pictures. [image]

[/image]

[image]

[/image]

Posted By: Thumperdart

Re: Spark Plug - 01/28/15 03:57 AM

Quote:

I didn't see where they made contact with the piston to bend or brake. The 3 plugs picture were list this, the other 5 were normal. Since all the plugs had the same about of runs on them, if they were worn, wouldn't all of the plugs be about the same or no? Here are a few pictures. [image][/image]

[image][/image]

Looks like someone cut their own ground straps to me.......

Posted By: sixpackgut

Re: Spark Plug - 01/28/15 05:08 AM

I use to run that plug when they were made in USA. When they started to be made in china or wherever, i will say around 2005, I quit buying them and started buying the AR plugs. I have never seen that happen and I have seen pistons hit plugs but it usually just bends the strap

Posted By: Crizila

Re: Spark Plug - 01/28/15 04:47 PM

Quote:

Quote:

I didn't see where they made contact with the piston to bend or brake. The 3 plugs picture were list this, the other 5 were normal. Since all the plugs had the same about of runs on them, if they were worn, wouldn't all of the plugs be about the same or no? Here are a few pictures. [image][/image]

[image][/image]

Looks like someone cut their own ground straps to me.......

Man manipulated. Not even all the same. Strange.

Posted By: MR_P_BODY

Re: Spark Plug - 01/28/15 05:03 PM

I see weld splatter on the one washer... but those
ground straps look like the material is messed up..
they look like carbonized.. the grain structure looks
really goofy.. I would say that it burnt off..
was it the same cyls that did it a second time

Posted By: pittsburghracer

Re: Spark Plug - 01/28/15 05:21 PM

Kinda off topic but why are you mixing race gas with that compression. Did you ever do a cranking compression test?

Posted By: DusterKid

Re: Spark Plug - 01/28/15 06:13 PM

Def not done by man, the other 5 plugs look normal.

I wish I could remember which cylinders it was last time to see if it is a trend with the same cylinder, but I don't remember.

I mix race gas with pump gas because I was having issues with the fuel boiling when the weather would get hot ever since they started to put ethanol in fuel.

Ignition is an MSD 6AL box, running MSD street fire 8 mm plug wires.

Posted By: Locomotion

Re: Spark Plug - 01/28/15 07:05 PM

I've had a few do that, but I believe that I may have weakened the straps by bending them around so the tip of the ground strap was centered over the electrode or even a bit further back. My ground strap were almost verticle, then made a sharper turn towards the electrode. I also tend to run lean, so it could be a combination of what caused it.

If it was "contact", the electrodes would likely have been bent down more.

Posted By: Crizila

Re: Spark Plug - 01/28/15 07:15 PM

Quote:

Def not done by man, the other 5 plugs look normal.

I wish I could remember which cylinders it was last time to see if it is a trend with the same cylinder, but I don't remember.

I mix race gas with pump gas because I was having issues with the fuel boiling when the weather would get hot ever since they started to put ethanol in fuel.

Ignition is an MSD 6AL box, running MSD street fire 8 mm plug wires.

Well, if they were "blown off", you would think you would see marks on the pistons / combustion chamber areas?? Did they all just roll out the exhaust without hitting anything? I guess that's possible? From the slant of the electrodes, looks like they were firing, even with those gigantic gaps - and the edges of the ground straps are still very crisp. Something is missing ( info ) from somewhere.