Hello All:

Long time reader of the forum---so much helpful info over the years -- first time posting!

Reaching out for some thoughts on some recent strangeness with a routine spark plug change.

The car is a 1967 Plymouth Valiant---225 Auto Trans

As recommends time and time again on this forum I decided to swap out the old Champion RN14YC plugs with the NGK ZFR5N minus the crush washers gaped at .035. Following this procedure and recommendation.

http://www.slantsix.org/forum/viewtopic ... t=#p138010

Car has a Petronix ignition conversion kit—everything else is stock.

With the Champions the car ran smooth but has a noticeable hesitation on light acceleration.
Carb is the correct Holley 1920 and was recently rebuilt.

Immediately after install the idle was rough and the engine had a noticeable miss.

Took for a spin. Much better acceleration—terrible idle—but not stalling.

Decided I would check the gap and change the wires thinking they may have been damaged in the install.

Upon removing the plugs to re-gap, much to my horror, I found the plug in the number 3 cylinder to be damaged—the electrode is bent.

https://drive.google.com/open?id=1N1Noj ... RncIijeJ0c

Spark plug tubes are in good shape and I replaced the gaskets prior to installing the NGKs.


Fearing engine damage, I Reinstalled the old Champions with the crush washers on and idle is smooth again and things SEEM fine.

However upon installing the old Champions I found one with a slightly misaligned electrode—unfortunately I do not know if it came for cylinder number 3. (Did not reinstall)

https://drive.google.com/open?id=1ZkbXs ... EApBLr-vrt

https://drive.google.com/open?id=1oH98t ... XtwOxidzMf

But so many questions....

What hit the plug?

What happened that would cause this?

Why is one of the old plugs misaligned ?

What plugs should I run?

Did I cause engine damage that I am not aware of yet?

Why do I have a light acceleration hesitation?

How was it possible that higher RPM performance was good and acceleration was smooth with a bent plug and a likely a dead cylinder...?

The engine runs runs well. Sounds good. Uses no oil. No smoke. No water. Mileage on engine and car is unknown but assumed to be low. Ive owned for 12 years....

This is confusing.

Thoughts ?


Thanks.

Is something bouncing around in cylinder 3? Do you have access to a bore scope?

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Casually looking for a Clifford hyperpak intake for cheap.

You could buy an endoscope on ebay or amazon for around $20
You install the app on laptop and plug in the usb cable from e scope then you can see the video on computer screen. The wireless one can be used on smartphone or laptop.

I’ll order one...but what could be in there that would not be causing other issues? No weird sounds as all.

The NGK looked worse than the champion. The champion was just a little off center. The Gap on the NGK was 0. It was right against the electrode.

Carbon build up is a possibility.

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63 Plymouth Valiant Wagon

Looking at the backstrap on the NGK it looks like it has a couple of contact ridges...I would suspect a bolt or something... It takes a bit
for this to happen on a stock 60's engine, I know on a 70's 225 shaved .100 a 5/16" nut laying on the piston face will stop the piston when
the intake valve is opening and the cam lift is .435 with proper lash... so what ever it is...it has to be close to 3/8" or so to make contact
with the NGK or a combination of something like a washer and carbon build up... too bad our engines don't have large exhaust valves or
it would have gotten blown out during aggressive driving...(seen that happen on a 383...lol)

Endo scope will help, if its iron based and can fit through the spark plug hole a magnetic probe might get it... anything bigger will require
the head coming off...FYI.

Could they have changed the extended tip to be longer? I would measure and see how much further the new plug sits down in there relative to the old plug. Probably not, but worth a look. Hard to see that carbon buildup would do it, but maybe. If there were something loose in there, the plug type would not matter and you would hear something while it's running.

Lou

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Home of Slant6-powered fun machines since 1988

No. The ZFR5N is the same as it's always been.

Also, they fer sher didn't change the design long enough to make one spark plug for the OP's № 3 cylinder, then change it back again. I think the problem is with the OP's engine, not with the spark plugs. It's also not carbon buildup doing it.
OP stated one of his ordinary Champion plugs got bent, too—and from the pics we can see his Champions had washers on them that weren't supposed to be there, pulling the electrodes even further away from the piston.
Maybe or not.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Here's my opinion. It could be wrong. Judging from the grungy looks of that 'new' plug, and the bent electrode, and the fact that you say it has happened other times.....

I think you're a sloppy mechanic and keep bending the electrodes when you install the plugs. I don't think there is any mechanical damage going on inside the engine.

You should be using a clean socket that has a rubber foam piece inside that holds the plug in the socket. You should take the new, clean plug, check the gap, and then give it a final wiping with a clean cloth to remove any fingerprints etc. The new plug is clean coming out of the box...it should never get dirty anyway. Then, it should be installed gently and without fanfare such that the electrode never touches anything....and if it does touch, it touches so lightly that it doesn't have a chance of bending.

Plugs that get bent electrodes from internal strife seldom bend that nicely. IMO that bend is from bonking it against something prior to insertion.

I have a bore scope ordered---just to see what is going on...

I cannot say for certain the Champion was from cylinder 3---When I change plugs I always keep them in order--but as luck would have it they fell off the table and got mixed up.

The damaged Champion was misaligned - but not smashed like the NGK.

I have since driven the car 20 miles and pulled the number 3 plug (Champion)---no damage noted. Going to drive tonight.
Idles smooth...still has a nasty low RPM hesitation....but runs nice at highway speed and sounds as it should.

Was considering installing another NGK just to see...but I am a little hesitant...this is still a very good running engine

Could a crushed / bad spark plug tube have allowed the NGK to sit lower than it should have..?

For years plugs with the crush washer have been installed---could they have damaged the tubes..? or am I thinking of this wrong..?

THANK YOU all for the replies, it is much appreciated!

GregCon:

I wish you were correct, but Im not sure you are here....

The Champions I removed had been in the car for about 12 years....I may have bent it back then..who knows...I'd need a time machine...but that's a different forum....

None of the NGKs were mis-handled during the install----They were all gaped properly at .035

I have 3 slant six powered cars and some other stuff...this is not the first time I've installed plugs...not great at it, but generally careful---Id love this to be on my mistake...I hope it is

I should have cleaned up that plug for the photoshoot...

However, I would agree that I am not convinced something is banging around in the engine

Thanks

There's a troll living in your № 3 cylinder, behind the intake valve. Aside from smelling terrible, he's a bigot—he doesn't like Japanese-brand spark plugs, so after you install the spark plug but before you start the engine he climbs into the cylinder, bends the electrode, then runs and hides behind the valve again.
Probably accelerator pump and/or vacuum advance
How about un-bending the NGK plug you have and putting it in again to see what will happen? It doesn't look fatally killed to death.
Can't imagine how. The spark plug tube is very thin aluminum. What actually stops the plug when it's fully screwed in is the iron cylinder head.
Might have chewed 'em up slightly, but almost certainly not enough to make any problem like this.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I would just unbend the electrode and put it back in to try.

Lou

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Home of Slant6-powered fun machines since 1988

Dan:
For now I think I was able to convince the bigoted, smelly troll in my 225 that Japanese spark plugs are good and we should give them a chance.

I cleaned, reset the gap to .035 and reinstalled the NGKs.

Very smooth idle...still has a nasty low RPM hesitation (especially when cold) but more responsiveness at the higher end---especially full-throttle downshifting to 2nd gear.

Ordered a vacuum advance---current one appears to be original. I assume the distributor will need pulled? Hoping this will cure the low RPM hesitation.

Had hesitation with the old carb...rebuilt carb (different, but correct number) still has same hesitation...so I'm thinking ignition/timing related.

Will check the timing as well---what is the specific recommendation of the folks here for a fully stock 1967 225 auto trans, Holley 1920..?

When the borescope arrives, Ill pull and inspect the plug, look in cyl 3 and will post a picture....who knows maybe we will see the troll...

Thanks again for the help.

Yes, you'll need to pull the distributor, but it would've been a good idea to test your present vacuum advance to see if it even needs replacing. Maybe it's fine. Maybe it's just your vacuum advance hose that has a hole in it, or isn't hooked to the correct carb port, or it's on the correct port but that port isn't getting vacuum because of a problem in the carb, or…
Could be. But did you verify your accelerator pump is working (at all/properly)?
5° Before Top Dead Centre, trans in Park and engine idling at 650 rpm and the vacuum advance hose pulled off the distributor and plugged (of course, here again, the hose needs to not have any holes or cracks).

Tune-up parts and technique suggestions are in this post. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.