Has anyone ever had a plug gap close under WOT?

bigmoose

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How much boost? That can only happen from detonation. I'd be worried about that Cylinder now.

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big dad

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What plug are you running? Check the top of the piston and the cylinder wall with a video scope for damage or any marks. My first guess would be that something is kissing the ground electrode which is not good.
 

Weather Man

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That is knock. On 91 I could only do 12 psi and 15 degree's timing on my turbo setup. Anymore boost or timing and I had knock. Back some timing out.
 

01yellercobra

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Yep. Happened on my old engine. When I pulled it apart I found signs of detonation. Might be worth having your injectors flowed and cleaned.

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BlckBox04

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definitely have a problem with that cylinder. all good advise in this thread.
 

01yellercobra

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Sounds like a broken ring land......don't ask me how I know!!o_O

Doesn't have to be a broken anything. Mine had the marks from detonation, but nothing was broken thankfully. But then if he keeps going something could end up broken.
 

Coosawjack

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Scope it and you may be surprised......mine ran good with ring lands broken on 3 pistons and a bent rod!!:eek:

Plug gaps close when hit by the piston pieces that incidentally will end up in your intake manifold!!o_O

I hope I'm wrong but it's hard to believe preignition would close a plug gap??:confused:
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bigmoose

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According to NGK when a plug gap is closed its from detonation. If you broke off pieces of your piston you'd hear it afterwards.

"Hot spots will allow the air/fuel mixture to pre-ignite. As the piston is being forced upward by mechanical action of the connecting rod, the pre-ignited explosion will try to force the piston downward. If the piston can't go up (because of the force of the premature explosion) and it can't go down (because of the upward motion of the connecting rod), the piston will rattle from side to side. The resulting shock wave causes an audible pinging sound. This is detonation. Most of the damage that an engine sustains when "detonating" is from excessive heat. The spark plug is damaged by both the elevated temperatures and the accompanying shock wave, or concussion"

http://www.ngksparkplugs.ca/tech-info-spark-plugs.cfm

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01yellercobra

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Scope it and you may be surprised......mine ran good with ring lands broken on 3 pistons and a bent rod!!:eek:

Plug gaps close when hit by the piston pieces that incidentally will end up in your intake manifold!!o_O

I already had my engine apart. None of the pistons or rings were broken. There were marks of detonation all over the piston though. I always thought it was from the heat causing the electrode to soften and give. But bigmoose's post makes sense.
 

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