Henry3959

Sharkey

iTrader: (1)

well assuming it didnt get put in like that, id have to guess you broke a piston and it smashed the plug. looks like there is some aluminum speckles on the porcelain

Henry3959

Nope... wasn't put in like that. I was at the top of second just going into third WOT when power dropped off a bit and then the CEL and appropriate codes set. Plug is black from driving home around 2 miles.

Not a piston strike....

Sharkey

iTrader: (1)

did you look around that hole with a bore scope? any time ive had a plug gap close up in an ecotec with stock pistons it was missing a piece of piston.

umrdyldo

iTrader: (1)

A squirrel.

TELL US ALREADY

Slowbalt2000

iTrader: (1)

Guarantee it was a broken piston ring

jdbaugh1

iTrader: (1)

In for what happened. Also, what spark plugs and heat range are those?

Henry3959

Yup, took my 5mm Boroscope to it after pulling all plugs but that cylinder was really wet and reflecting back. Bead blasted the plug , put it back in and it ran great. Drove it the rest of the day and re-pulled the plug to find it was looking like all the rest again.

Boroscoped the piston all the way around and the cylinder wall..... Nothing. Been driving it back and forth to work the last 5 days. Uploaded the log file to show you how nice the fuel is trimmed.

Running the NGK V-Power LFR6A-11's. Although the incorrect seat as discussed earlier, they are burning great.

Henry3959

That would actually be a good clue... Squirrel... Nuts... cleaning

I have only seen this happen 1 other time in the dealership on a carbureted 454 after a tune up.

royce777

iTrader: (29)

I would run a compression test

Henry3959

Sorry... did that after pulling the plugs the second time. Didn't do it right away as #1 cylinder had not been firing for a while. 130-135 at the 4th rotation. 2,3 and 4 were no higher. We don't get as good of compression tests at this elevation if these are low but with them all being even I moved on.

Think what would result in no damage and the ground electrode after cleaning had no strike marks. What would close it and not leave a nick.

Henry3959

Damn.... I was sure after seeing nothing, a chunk of carbon let loose as I have seen happen before. Boroscoped again tonight and looked and looked, comparing to piston 2 and saw a small reflection. Got right on top of the edge of the piston and sure as crap, there is a small, and I mean small piece of piston right at the valve relief missing. The reflection is the ring of c.ourse. It was so sooty after running with no combustion it mast have been darker

I have been wanting to upgrade pistons and rods so I guess it is now time. Did a compression test again and still the same. #1 is not down but maybe 3 pounds from the rest. I wonder how often this happens and goes unnoticed if it misses the plug?

Slowbalt2000

iTrader: (1)

Time for custom pistons

Henry3959

Sure's the hell can't put OEM back in if this is common. Googled a build a guy was doing and didn't know he had the same failure till he took it apart for the upgrades. I'm glad it found the plug on the way out but hope it didn't get between an exhaust valve and seat once on the way out. I hope forged don't do this. I also saw an LNF with the same area damaged and aren't those forged from GM?

user 72239

iTrader: (4)

Were you ripping around when it was hot as ****?

Sharkey

iTrader: (1)

the problem isnt the pistons being weak, its the ring gaps are too tight for boost. what happens is with the extra heat the rings will expand more and when the end gaps butt together the ring has to go somewhere so it pushes up breaking the piston. the ecotecs have the top ring so close to the top of the piston it breaks so easily. other engines with the top ring lower down the piston will take a little more before it breaks the piston, however in the meantime it will scuff the hell out of the cylinder wall.

i think the stock pistons would last a lot longer in the 2.2 and 2.4 under boost if you opened the ring gap up. factory top ring gap is between .008-.014", if they were opened up around .018-.022" for the top ring they would be a lot happier.

chevygirl2006

They do last. At least for my car. I ran 17psi on stock 2.4 Internals for 2 years. Now 22psi currently. Multiple track passes and a lot of beating on. I recently checked compression and it's basically perfect across all 4 cylinders and car runs great. Could be the tune making it reliable. Who knows.

63 Nova SS

iTrader: (3)

How frequently you beat on it, and for how long, makes a difference. I would think the worst would be road course due to being in boost a lot, for several laps at a time.

chevygirl2006

Yes and his car has been boosted for like a month or two. And yes I've beat the crap out of my car in the 8 years I've had it. Lol.

jdbaugh1

iTrader: (1)

You are running the TVS on stock pistons?

chevygirl2006

Everything about my motor is stock. She's still kicking.

jdbaugh1

iTrader: (1)

HGT, if you're going to install pistons you may as well join the TVS club.

Slowbalt2000

iTrader: (1)

Stock le5 pistons are not weak, ive put some stock motors through hell and the block always breaks first. Either the piston had a manufacturing defect or the timing was a bit much.

Henry3959

I-25 doesn't allow that anymore, I would rather bask in the cold AC back and forth to work. This actually happened last weekend when it was a little cooler. I have had zero knock and am still keeping my timing conservative on 91 octane so I can't imagine that was the issue. Fuel trim is a little on the rich side in PE so I guess it just doesn't like the 6800 RPM shift point to second.

I'm not surprised considering the 130K miles and how weak those corners look. I suppose if I keep the boost to 5 psi or so I should be able to keep the other 3 edges on till I can build another engine. I don't want to be rushed over a weekend so I am looking for another 2.4 locally and thing I found the same year etc.

Slowbalt2000

iTrader: (1)

Get an 06-07 le5