96 mer cruser 5.7 burned piston

M

moparmanglhs

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Feb 9, 2013
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Im trying to find out what is wrong before i put this thing back together again. I hope someone can help. Eng. ran strong and idles smooth for several seasons then one day running it started hammering and pushing.oil out dipstick and breathers. pulled heads and found #6 piston burnt through. other pistons were fine. had eng. bored and rebuilt by eng.shop. reinstalled eng. and after about 8 hrs. on the eng. same thing happened to the same cyl. someone told me the thunderbolt v ign can cause this. Any one know of this problem ?
 
Don S

Don S

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Re: 96 mer cruser 5.7 burned piston

Timing, running lean, water, hard to say without seeing the damage.
 
Bondo

Bondo

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Re: 96 mer cruser 5.7 burned piston

Ayuh,.... Welcome Aboard,.... My guess is, You've got a Detonation problem,....

A Lean condition caused by bad fuel is probably the #1 cause...
 
achris

achris

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Re: 96 mer cruser 5.7 burned piston

Bond-o said:
Ayuh,.... Welcome Aboard,.... My guess is, You've got a Detonation problem,....

A Lean condition caused by bad fuel is probably the #1 cause...
Click to expand...

or an overloaded engine... What rev did it make at full noise before the piston left the building?

If it was low grade fuel the knock sensor on the TB-V would have retarded the timing....

Chris.......
 
M

moparmanglhs

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Feb 9, 2013
Messages
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Re: 96 mer cruser 5.7 burned piston

Bond-o said:
Ayuh,.... Welcome Aboard,.... My guess is, You've got a Detonation problem,....

A Lean condition caused by bad fuel is probably the #1 cause...
Click to expand...

Thanks for any ideas or advice on this problem. The damage looks like it could be detonation but it only happened in one hole. #6 both times. makes me think it could be the ing. system firing that plug to early but Ive never heared of that happening to one cyl. Fuel was fresh both times out.
 
M

moparmanglhs

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Feb 9, 2013
Messages
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Re: 96 mer cruser 5.7 burned piston

achris said:
or an overloaded engine... What rev did it make at full noise before the piston left the building?

If it was low grade fuel the knock sensor on the TB-V would have retarded the timing....

Chris.......
Click to expand...

Thanks Chris. Nothing came apart. the piston began to melt and burn, molten alum. spatered cyl wall and head. we were running about 4200 to 4500 at the time
 
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