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  #1  
Old 09-12-2003, 07:32 PM
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jleilich jleilich is offline
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Help is my wallet about to get alot lighter? help!

ok , went to the track about a month ago. my car was running fine, then my last run it wouldnt idle.. turned out to be a float all the way up and the bowl was full on my 850 demon. Don said it was my N/S so i changed it. ran better but then it was surging all the time and not running right. the carb was ok, so i changed all my plugs.. then oh no..!! my number 3 plug , the little arm over the electrode was touching.. (it was at 0 gap) didnt notice any other plugs damaged. did i wreck a piston, or worse wreck a piston and damage my aluminum heads? the runs fine now. Im afraid to race it again. friend of mine said put a leak down tester on it. but im thinking just pull the head and do a visual check.. what is eveyone's opinion.??????

by the way.. i think the N/S and the plug were just coincidental. dont think they were related...
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Old 09-12-2003, 08:02 PM
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You say it's running fine now. No knocks ect?

I don't think you need to do anything. Something may have hit the electrode, but, it for sure wasn't the piston. There isn't enough give in everything, unless you grenaded it. But if you grenaded it, it wouldn't be fine with just a plug change.

Do a compression test if you want' but since the running cleared up after you changed the plug, it would seem obvious that there is compression on that cylinder. If there wasn't then the running would be unchanged with the plug.

You may want to look at a few things, like pushrods, rockers ect, but I don't think you'll find anything.
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Old 09-13-2003, 04:20 PM
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dwc43 dwc43 is offline
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I'd pull that head and inspect and then do some serious measuring. Plugs just dont go to 0 gap by them selfs. Something hit it and that can only be a piston. Check your piston to valve and piston the head clearences. It's possible it hit at high rpm.
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Old 09-13-2003, 07:21 PM
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I think the chances of a piston moving up into the combustion chamber, on a closed chamber big block head, are pretty slim.

How could it have come up and hit the plug, but not the head, and now run fine??

Not a realistic scenario, unless I'm missing something.
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Old 09-13-2003, 07:26 PM
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Dome pistons and incorrect clearences. Heat exspands parts and rods stretch especially if they are aluminum.
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Old 09-13-2003, 07:35 PM
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I suppose, but...

It's a 440 with closed eddy heads, and 9.5:1 comp.

That said, the pistons can't be domed(or the compression would be higher) And if the quench was done right at time of assembly, the piston is already coming within .040 of the head all the time.(in the quench area)

Jleilich, who assembled the motor? Any idea on pistons used, deck clearance, ect?
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Old 09-13-2003, 07:40 PM
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Where did you get the 9.5 to 1 cr figure? Did you misread the Dynamic 9.5 converter part or did I miss something too?
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Old 09-13-2003, 07:44 PM
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Good point.

Again, what are the specs on the motor?

I guess what I'm wondering is how a piston could have moved enough to hit a plug, yet not enough to take up the .040" quench clearance on the closed area of the head.
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Old 09-14-2003, 06:13 AM
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ttraut@unlockit ttraut@unlockit is offline
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wow

If this had happened to ME, I would have suspected that I dropped the plug on installation OR on removal. But I'm dealing with an ignoramus for a mechanic...

Terry
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Old 09-14-2003, 08:33 PM
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Glen440 Glen440 is offline
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My guess is something passed through the engine. If it was a clearance prob more than likely you would have done more than 1 plug. I would do a comp test and if it passes keep on racing.
Most likely a valve would hit a piston way before the piston could hit a plug.
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Old 09-15-2003, 12:03 PM
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hey guys,, no the compression is about 10.5:1 the converter is 9.5 in. ... a local engine builder with a very good reputation built my motor, I thought of me possibly hitting the electrode on somthing or dropping it, but then it would have been running like crap the whole time.

somthing had to have hit it , but like i said the car runs great now. no problems.. dunno the mystery builds,, I probably need to do a visual check just to be sure.. a friend of mine is a service manager at a BMW dealer. he said he's got a tiny camera that is used that you can stick in your spark plug hole and look around. i think im gonna ask if i can use that.. heck i think it would be cool just to use it anyhow.
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