frito1

iTrader: (12)

This is my #7 piston after about ~1200 miles and quite a few track runs. NA motor. Why?

memphisTa

iTrader: (2)

Only 1200 miles....you must have just had it built. Man that sucks

bearcatt

iTrader: (41)

Looks like detonation.




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frito1

iTrader: (12)

The '04 shortblock had 27,000 miles on it. I added ARP 2000 rod bolts and built from there. Yeah, it didn't stay in the engine bay for very long...

Would the stock LS1 PCV system dump in enough oil to cause that much detonation? I know it dumped a bunch after the piston came apart from all the blowby

94'BLKBRD

iTrader: (76)

Damn that sucks

Beaflag VonRathburg

iTrader: (176)

Called it in the last thread:

That sucks, but yes it looks like detonation even more now that we have pictures.

vettenuts

iTrader: (4)

I don't think it was detonation (unless it was more than this cylinder). Looking at the white exhaust valves in the other cylinders I would think you were too lean and #7 usually is the first to let go when this happens.

04gtod

iTrader: (3)

Same thing happened to me. Probably lean. #7 is the leanest cylinder due to intake manifold design.

frito1

iTrader: (12)

To be somewhat fair, I have to say that I drove the car home from the track not knowing I had serious issues like this It never made any bad noises or nothing too bad anyhow. Well it is a ~50 mile trip back home. The broken piece of piston hit the spark plug making it go no gap. That was causing a complete miss (hence all the black fouling) and raw fuel going out the headers. o2's saw that raw fuel probably leaned up everybody while going home?

BTW, thanks for you help, Vette setting up the YT's. I had a perfect line across the middle of the valve stems!

dlove

iTrader: (23)

car was dialed in with about 27-28 degrees (pretty much a stock table) and an air fuel of 12.9. We ran at the track with 12.5-7 afr just to try and it didnt pick up any.

I think he told me the rest of the plugs looked ok.

redtail2426

iTrader: (10)

did the previous owner spray on the shorblock.??

frito1

iTrader: (12)

That is a question I'm trying to get answered. I bought it out of state. I have several friends sticking me in the sides saying my motor didn't last very long and it kind of sucks because I didn't have anything to do with this (that I know of). I really want to figure why this happened so it doesn't happen again. Do I need to have the injectors flow checked??

BTW, SCR is 11.33:1 and DCR is 8.5:1 and 91-92 octane was always ran. I should have been plenty safe there.

NOW, I have to figure out where I go from here. I still have the stock longblock with 120k on it. And I have this longblock with a bad piston. The sleeve is fine believe it or not. I'm not looking to spend a ton unless I have to (I have to buy a FLT trans this winter too). I was happy with the power. I do not plan on spraying. What do I do with this mess? TIA

99blancoSS

iTrader: (115)

I'll pm you

Grimes

iTrader: (3)

I would get some forged pistons at least (rods too if you have the cash), and use one of the short blocks you have now.

bjamick

iTrader: (31)

Ya you need to find out why it went so lean in that particular cylinder. I know the intake design causes this but only 1200 miles .

SS4Luck

iTrader: (10)

i just had to replace 5 and 7 because of the same thing... they even broked in the same spots

redtail2426

iTrader: (10)

okay well then 2 NA motors losing piston skirts..Its really not as easy as people think to run an NA motor lean enough to do serious damage like that,just not enough cylinder pressure..Maybe its a cooling issue in that back corner???

frito1

iTrader: (12)

I'm up for more discussion and talk about it. An engine guy I know is calling my situation detonation all the way. He says that my oil mist was causing the uncontrollable detonation. The oil will flash when it hits the combustion chamber and the computer couldn't pull out enough timing. And the log showed the car was pulling timing out.

bearcatt

iTrader: (41)

What about your full system ?

Were you using the stock fuel pump and injectors, if so what about
your duty cycle ?

And

I don't know... running your AFR in the high 12 isn't exactly safe
with 91 pisstane. All that it takes is a little bit of sediment in the
fuel and it's over.

Running 91 pisstane ... it's usually much safer to stay in the mid 11s
at most.

Just my 2 cents.


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frito1

iTrader: (12)

My sig shows I've got 42lb injectors. With a stock fuel pump. My tuner would know my cycle duty. I'm sure it's fairly low.

11's AFR on a NA motor seems pig fat rich to me! We used to run 13.5:1 AFR all day long on our pump gas 12:1 SCR racing atvs. I'll have to read up on 11's AFR.