4 spark plugs with 0 gap
 

1970 ys 400. Mild cam, Headers, quadrajet with cast iron intake.
Just before putting the car away this past fall I had an issue after starting it. Ran very rough like missing a few cylinders. Pulled the plugs and found 1,7,4, and 6 with the ground electrode bent over and touching the center electrode. No mechanical damage noticed. Other 4 plugs were fine and burning normal. Light tan color. Put new plugs in and it's fine. No noise and running strong and smooth. A little research and it may be a detonation issue? Being a dual plane intake is one side of my carb malfunctioning? Anyone ever run into this? Seems to run fine now but I'm worried it could happen again with more serious consequences.
Thanks in advance,
Joe.

Pictures of plugs?

Here's 3. 1st pic shows one of the good plugs.

Running stock HEI. Gapped at 45.

I can't think of anything doing that except mechanical contact.

1746 would be one side of a dual plane. Hmmmm
The good plug gap looks kinda wide.

Ok so if something like a small nut fell in one side of the manifold, it could possibly bouce around and go between those 4 cylinder hitting those plugs before shooting out the exhaust. Sounds unlikely but possible?

I hope there's nothing floating around in those bores...

My knee-jerk reaction was that this would have to be a mechanical thing... but I have been wrong many times before...

Keep us posted on how the new plugs are doing while we all scratch our heads over this. Reminds me of 25 years ago and timing belt breakage on a certain 4 cylinder car (not ours) that I worked on, except the valves and plugs were flattened and pistons cracked.

My best guess is that you opened up the gap and the electrode hit the plug hole threads while screwing them in, closing the gap a good bit causing them to eventually foul. Then when you wound them out they got shut completely from the deposits. :Ithink:

:confused2:noidea:

Are there any thread marks on the back side of the electrodes that are bent shut?

Would a lean condition cause the ground electrode to get super hot and bend? I just find it weird that it coincides with the upper plenum of the intake manifold. Not Pontiac but on searching the internet there is reference of detonation overheating the tip of the plug and basically hammering it. I would think if it was detonation it would affect all cylinders.

That's what's baffling there are no marks on the tip of the plug. Almost like it's melted and just dropped down.

I am not referring to the tip, but the part that is directly above the threads.

If the bend of the electrode was such that it stuck out past the threads, screwing the plug in would push the electrode in/down.

something had to hit them.Tom

Gremlins, I've had lots of them messing around in my cars.

Subscribed because I love a good mind teaser!

Did my neighbor put the plugs in? :D

1746. what are the chances. thats one side of a dual plane manifold. flying debrie will be issolated to one side of the manifold because of the divider. seems freaky, BUT 1746. that's too much of a coinidence. if you're not sure what im talking about, one side of a dual plane is 1746, the other is 2358. coincidence?

Correlation to the intake feed split can't be a coincidence, I agree.

carb parts falling into the engine? How's it running now?

I've seen plugs come out of the box like that.

Had a problem like that with the last motor. I bought a scope camera from Harbor freight, went down the spark plug hole and looked at the piston and head. I my case I had a broken piston piece that closed the gap on the plug. It is worth checking it out for the $ 50 I spent with the coupon.

you can get bore scopes super cheap these days...
some of them work with your smartphone (making the smartphone the screen).

Is the car kept/ stored on your property where otters have access to it?
A friend two years ago who stores with others at a big garage had a strange sound coming from under the Hood one day while driving only, and went nuts trying to figure out what was going on only to find that a buddy that stored at that same garage had cable tied a Harmonica to the radiator support in the nose of the car. Lol!!!!

That's hysterical! Ingenious. Downright evil!

I know , I still to this day near wet myself when I think about it!!!

On our crate motor stock car, a crew member took off the air box and unbeknown to us a few small pebbles fell into the intake. During hot laps the driver noticed a miss. We checked the headers and found the coolest one. We checked the sparkplug and the electrode was grouned out. Regapped the plug and won the feature race.

Stuff falling into the cyls is fairly unlikely, especially the whole bank. If that much 'stuff' fell off the carb, like as in carb parts, I doubt it would run at all. Like what kind of parts would distribute among all cyls on one side?

Valves move pretty fast, would think that they would be damaged from foreign debris.

I'd have to guess that the plugs were either installed that way, or carbon chunks did it. Maybe that side leaned out, loosened some carbon in the chamber, and made contact with the electrodes. That could happen and not cause perm damage to valve, etc.

.

Thanks, it wasn't one bank. It was both sides but 1 plane of the intake manifold. That's why I keep thinking a mixture problem. Plugs have been in for over 2 years. Maybe 7500 miles. Car ran great up until this problem. Once I replaced the plugs the car ran great again. Still pulls hard and idles fine. I've got maybe 10 miles on these plugs then I put it away for the winter. No mechanical damage to the end of the plug.
Baffling.

You're having detonation issues, the detonation cracked piston rings and Bends spark plug electrodes. What kind of heads do you have ? What is the compression ratio and what's the exact configuration of your cam. I've had a spark plug bend on me once but then the engine blew up as well after that, meaning some of the piston rings cracked

This is what I was afraid of. The heads are 13s and the cam is:

Just run 94 octane if you can, do a compression test and a leak down test to monitor your combustion Chamber and rings. .. add a little octane booster to be on the safe side and don't run too much spark Advance somewhere around 32 to 34. Don't run any vacuum advance, pull that vacuum hose off and cap it. Just run strictly mechanical.

You might have sucked up a mouse or rats nest, enough crap to bend a ground strap but not enough to damage the engine.

You'd be surprised what can take place in an engine when spinning at high RPMs. I had my blower motor lean out at the top of third gear one night. It melted just one piston but pieces of that melted piston was in bedded in every piston on the right bank of the engine. That manifold is divided side to side with a ramp in the center. So at 6500 RPM pieces of that one piston made it's way into three other cylinders! The valves were untouched it must be some weird reversions going on for that to happen with boost pushing back at it. You may have had something fall into that side of the manifold and at certain Rpm's reversion did the rest. If it wasn't metal you would never hear it.

Check to make sure the center electrodes are not broken.

We had a Champion plug one time that would gradually lose the gap and cause a miss. After a couple iterations we finally replaced it and set it in the "broken parts display".

I was messing around with it one day and noticed you could push the electrode down (as if you were gapping it) and it would stay there for a little while, gradually working it's way back up until it hit the side electrode. It was like it had a little spring inside there.

I still have it. I was tempted to cut it up to see what was going on with it but decided I'd rather have it as a discussion piece.

K

That's one the craziest things I've every heard, wow :confused2

Any updates?





http://race-1.com/p-26201-what-shoul...ug-gap-be.html

Nothing yet. Weather is still not conducive to enjoying classic cars. Hopefully in the next few weeks I can get back to it. It's 18* with 30 mph winds at the moment. Hi of 16* tomorrow. :(

I feel it here too! :snow:

This one has me wondering. Saw the link I provided and your issue came to mind.