How did THIS happen to my plug? BROKEN PISTONS!

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frosty_the_punk

frosty_the_punk

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Noticing a lot of ticking and some smoke out the exhaust in my freshly built 318. have a couple hundred km on it now and thought I was in the clear.

WRONG

I Pull off the vacuum line to the rocker cover and notice HEAPS of blowby.

Crap....rings?

So I pull the plugs for a compression test and see THIS in number 5 :banghead:

All cylinders came up at 145-150 PSI except number 5 which was 110.

The porcelain is gone from the inside of the plug. but the electrode is still intact and has no signs of interference.

When I built the engine i had heaps of piston to valve clearance.
 

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Surely not the answer you want but...
The mfgr of the plug will argue that it was dropped and damaged before it was installed.
They have seen this too many times before. They cant prove you dropped it. You cant prove you didn't.
They will argue that nobody buys an extra plug just incase they might drop one. When it falls it lands on that end at closes the gap. If the porcelin wasn't damaged at impact it may have happened in you method of resetting the gap.
In a pefect world a spark plug would shatter like a light bulb when dropped and/or shop floors would be padded.
 
If there is a foreign object in that cylinder you'll find it when you remove the head.
 
I honestly couldn't say with absolute certainty that I never dropped the plug on the ground or that it never fell off the bench however nothing comes to mind.

I can guarantee that i will never do it from now on! lol.

I checked the gaps on each one and fitted it one at a time to my engine while it was on the stand.

In any case, I think I just had some bad luck.

Had the bore scope down there tonight, the chamber is fubar and I am expecting to have to sleeve the bore and do a VJ on the head..not to mention a new dome top piston.
 
I have been informed that this can be caused by detonation.

I definitely did have detonation at one point. and severe detonation at that!

my detonation was caused by the distributor hold down not being torqued down and the timing becoming advanced.

When this was rectified it ran for a few hundred km no worries. The plugs looked fine.

I guess you live, you learn. Next time I won't reuse plugs that have been subjected to detonation.
 
frosty_the_punk said:
I honestly couldn't say with absolute certainty that I never dropped the plug on the ground or that it never fell off the bench however nothing comes to mind.

I can guarantee that i will never do it from now on! lol.

I checked the gaps on each one and fitted it one at a time to my engine while it was on the stand.

In any case, I think I just had some bad luck.

Had the bore scope down there tonight, the chamber is fubar and I am expecting to have to sleeve the bore and do a VJ on the head..not to mention a new dome top piston.
Click to expand...

Year ago ( before cell phones ) a guy named Garner had a Camaro called Street Cleaner. I dont remember exactly what he had just completed, carb change or something. Anway..He left it running without the breather and went inside to use the phone. While he was away the engine knocked and stopped.
When he tore it down he found a small piece of allthread that held the breather on had vibrated out of its hole and fell into the engine. A piston was busted into several large pieces. Bottom line, anyone is subject to bad luck.
Here's wishing you good luck.
 
Thanks RedFish, yeah if it were cheap and easy to build and maintain these dinosaurs everyone would do it!

I'm going to kick it into overdrive and try to have this engine sleeved, honed, valve job and piston replaced and fitted back into the car for my first ever time out drag racing on December 1st.

I'll take all the luck I can get! :burnout:
 
frosty_the_punk said:
I have been informed that this can be caused by detonation.

I definitely did have detonation at one point. and severe detonation at that!

my detonation was caused by the distributor hold down not being torqued down and the timing becoming advanced.

When this was rectified it ran for a few hundred km no worries. The plugs looked fine.

I guess you live, you learn. Next time I won't reuse plugs that have been subjected to detonation.
Click to expand...


YUp - the porcelain cracked, then prbably started to fall out in pcs. It's not really common but it does happen.
 
My uneducated opinion is the plug was damaged before you put it in. This can happen during shipping and handling. My wife knocked off a bag containing a set of /6 plugs and a set of v8 plugs. Two days later she told me about almost spilling her coffee and knocking the bag off.
 
Yeah I'll never know for sure but I will certainly never underestimate the need for plugs to be in good nick from now on!

I swear I'll treat spark plugs like they're nitroglycerin after this!

At this point as much as it sucks having to pull the motor down I'm glad I found the problem so I can have a plan of attack and make it right.

And I feel I can rest a little easier feeling confident that it wasn't an assembly error on my part.

If not for the heartache these cars bring from time to time the joy would somehow be less deserved.
 
frosty_the_punk said:
I swear I'll treat spark plugs like they're nitroglycerin after this!.
Click to expand...

Hate to be the bearer of bad news, but it won't do you much good. As pointed out above, it could have been dropped anywhere from the plant of manufacture to the kid putting it on the shelf, or even taking it off to sell to YOU. Plugs are not packed in any protective way, as you've seen from the package yourself

If it's any comfort, broken plugs don't happen that often. I sold parts for 15 years in a previous life, and in my life I've only seen 4 or 5 plugs that seemed to have broken from no apparent cause.

One time, our old Nash Ambassador, AKA the inverted bathtub, broke a plug where the threads meed the shell. My father was an outboard mechanic (aluminum heads) so he was well aware of "not" overtightening plugs.

1954Nash-Ambassador-Custom-Country-Club.jpg
 
It probably won't do much good but it certainly can't do any harm :wink:
 
First time I've seen anything like that. Most plugs I've bought have a cardboard sleeve on the threaded portion of the plug that protects the electrode.

All the same, you still have a substantial compression drop in # 5. Can't say if it is a result of assembly of the engine or the plug coming apart. Apart from using a borescope to see if anything is apparent, it looks like you're going to have to pull it apart.

#-o
 
It happens to the best of us. I've dropped them and not checked a time or two and got bit, and I've re-gapped them a bunch after I looked and they were closed. My ex-wife's Ranger had a ping problem. It was fine running super unleaded, but pinged with the cheap stuff. A plung came apart, the porcelain got stuck at the edge of a piston and smacked the head, breaking the (hyper) piston and ruining the engine. The pcs were still stuck to the bottom of the cylinder head when i pulled it...lol.
 
The porcelin is gone because of detonation. Oil in the cylinder will cause extreme cases of denotation. I think you should put another plug in that hole and run it for a few minutes and recheck your compression. More than likely you now have a piston problem on that cylinder. The grooves that hold the ring pack are probably broken causing the blow by and oil in the cylinder. did you use stock cast pistons on this motor?
Steve
 
Cheers, This motor runs Keith black pistons with a dome top. (KB399)

I think the plug damage was was caused by detonation but it's always a good idea to handle plugs with care. I think this is a worst case scenario for plug failure.

The first few hours of running the motor it never burned any oil and the plugs looked like they would through normal use

I'd say the detonation caused the plugs to fail and then came the oil burning. not the other way around.

when I saw this plug I ran the motor with fresh plugs and it didn't change anything. that's when i checked it out with the bore scope monitor and saw all the damage to the combustion chamber. amazingly this plug was still working with no insulator and a bent electrod!

It's too difficult to accurately see how badly damaged the bore and piston is with the bore scope because they're both highly reflective. but the chamber looks FUBAR.

I'll have the head off in about 12 hours (I'm at work for the next 7) so I'll post pics then.
 
I would say the entire damage was caused by the denotation. Most likely the denotation caused the top of the piston to brake off and that rattled around in the chamber causeing more damage.
 
There's another theory now that my ring gaps may have touched and broken the top ring land off.

The motor did get pretty hot once during tuning and idling in between..

I did triple check the ring gaps and spent a good few hours file fitting them to make sure each one was spot on. I think from memory they were .039" but can't recall with certainty.

This is the first motor I've built from scratch and I triple checked everything and did everything by the book, cleaned everything to an almost surgical standard and followed all cam break-in procedures.

I'm anxious to have the head off now. I am hoping for the best but expecting the worst.
 
Unfortunately for me. When I removed the head on the left bank #3 and #5 were FUBAR.

The top ring lands had large chunks missing and there is some minor bore damage. at first glance it seems like I might get away with a Hone and 8 new pistons.

I'm unsure at this stage whether the damage was caused by detonation or tight ring gaps. or both.

Now I'm faced with the option of swapping Forged Icon IC845-30 pistons in there. which I'm confident can be weighted to match the pistons I have, eliminating the need for a rebalance of the rotating assembly.

KB399 advertised piston weight:541g, pin weight 132g. = 673 grams
IC845 advertised piston weight:525g, pin weight 118g. = 643 grams

This plus a cam swap should result in a superior motor to the one I originally built.

I'm thinking of a Hughes cam. HEH3742AL

Specs on it are
IVO 13.5
IVC 43.5
EVO 52
EVC 10

237/242 @ 50". Comp would be 10.25:1

Thoughts?
 
frosty_the_punk said:
Unfortunately for me. When I removed the head on the left bank #3 and #5 were FUBAR.

The top ring lands had large chunks missing and there is some minor bore damage. at first glance it seems like I might get away with a Hone and 8 new pistons.

I'm unsure at this stage whether the damage was caused by detonation or tight ring gaps. or both.

Now I'm faced with the option of swapping Forged Icon IC845-30 pistons in there. which I'm confident can be weighted to match the pistons I have, eliminating the need for a rebalance of the rotating assembly.

KB399 advertised piston weight:541g, pin weight 132g. = 673 grams
IC845 advertised piston weight:525g, pin weight 118g. = 643 grams

This plus a cam swap should result in a superior motor to the one I originally built.

I'm thinking of a Hughes cam. HEH3742AL

Specs on it are
IVO 13.5
IVC 43.5
EVO 52
EVC 10

237/242 @ 50". Comp would be 10.25:1

Thoughts?
Click to expand...

Ive run that cam, its on the small side 'lift fools u' and that int closing might put u back into detonation with that static comp ratio. id like to see a later int closing.jmo but what cam did u have in now? cause 150psi isnt high or too high for an open chamber head...so i guess ring gaps and or WAY TOO MUCH timing.
If you lost ring lands...id definitely think about what kind of top ring gap you had. you have to gap the top rings bigger with hypers, period, what you describe is the stereotypical consequence of not following piston manufactures recommendations for top ring gap.
examples..
My 340=kb243 4.070 gaped at .028
My 410 stroker kb356 4.040 gaped at .026
340 kb243 4.080 i just put together a member of this board=.030
 
In the above picture you can see the ring lands missing chunks on both cylinders.

The plug no longer looks to be the cause. Especially since the ring land is damaged on #3 as well where the plug was still intact somehow!

The detonation was caused by massively over-advanced timing. A loose distributor hold down on an early drive not long after running the camshaft in was the culprit. (my own stupid fault)

It is possible I didn't get the ring gaps right, I did file fit them myself and haven't done any before these. I'll have my machinist check them when I get the pistons out.

My current compression is 10.39:1. I also thought 150 PSI sounded friendly enough for 98 octane.

Cam is a comp Thumpr 227/241 @ .050"

IVO 11.5
IVC 35.5
EVO 52.5
EVC 8.5

There's no damage to either cylinder head, valves or valve seats. The bores look to me like they will be salvageable with a hone but I will have to get an expert opinion.
 
Just for those who are interested. The bore will be salvageable with a hone and I'm going for forged pistons and a solid cam.

Turns out the ring gaps were fine, The head gasket damage leads my engine builder/machinist to believe that the detonation is the culprit for the damage.

While the outcome remains the same, it's good to know that those rings gaps were right. :D
 
If I read this right you lost two cylinders side by side #3 and #5, sounds to me like you may have been leaking some coolent into the cylinders. Maybe something else to look at.

I have had one plug failure in 30 years of driving, I blew the ceramic insulator clear out of a plug in a slant six, the threads were still in the block so I just unscrewed it. These were old plugs and the gaps had opened up pretty good.
 
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