Collasped Piston???
- Thread starter Loafer409
- Start date
59elcooldsuv
Well Known Member
What do you mean by "collapsed"?
It's burnt a hole in the top?
The wrist pin bore has broken?
The ring lands have broken?
The rod has broken through the side of the crankcase?
The entire piston has simply vanished into thin air?
Until you define the word "collapsed" in the context of a piston's design or function, no one could possibly give you an answer.
I have never heard anyone describe a piston as "collapsed". I have seen many pistons which have been severely beaten , for example, stricken by valves after the timing chain "collapsed"; had their skirts ground away against the cyl bore after the piston rings "collapsed"; smashed from the underside by the conn rod after the wrist pin bosses "collapsed"; and a variety of other damage.
Can you be a bit more specific? Describe the exact symptoms as objectively as possible in terms normally used by most mechanics.
It's burnt a hole in the top?
The wrist pin bore has broken?
The ring lands have broken?
The rod has broken through the side of the crankcase?
The entire piston has simply vanished into thin air?
Until you define the word "collapsed" in the context of a piston's design or function, no one could possibly give you an answer.
I have never heard anyone describe a piston as "collapsed". I have seen many pistons which have been severely beaten , for example, stricken by valves after the timing chain "collapsed"; had their skirts ground away against the cyl bore after the piston rings "collapsed"; smashed from the underside by the conn rod after the wrist pin bosses "collapsed"; and a variety of other damage.
Can you be a bit more specific? Describe the exact symptoms as objectively as possible in terms normally used by most mechanics.
"Collapsed" refers to the piston skirt. The measurements at the bottom of the skirt will be less than specs by an amount greater than normal wear. A collapsed piston will usually have a noticeable knock. You may not be able to visually see it, but a micrometer will tell the story.
Ron
Ron
59elcooldsuv
Well Known Member
Amazing.
So is this caused by wear? Lack of lube? Or a factory defect? I've heard of severe wear and factory defects, just never heard it called "collapsed".
So is this caused by wear? Lack of lube? Or a factory defect? I've heard of severe wear and factory defects, just never heard it called "collapsed".
Follow up Question... What is the advisability of boring one cylinder. I have a buddy who has a marine V6, 4.3 with very few hours on it. Developed a knock tear down shows one piston/ cylinder badly scored, piston collapsed, all other look like new, crank/bearing looks like new, cam is good...Engine has less then 200 hrs, maybe even less then 100 hours... he wants to bore that cylinder, new rings and bearing through out and go for it...Sound resonable to me, I have never done one cylinder and not the rest...thoughts??? 
:
:one cylender
if everything looked good on the rest i would do just the one cylender as long as it cleaned up with little machining. .010-.020 is going to make a very small difference and I am sure it probally wouldn't even be noticable. now if it was a high rpm or race motor no way but in a boat i woud do it.
Jesse
if everything looked good on the rest i would do just the one cylender as long as it cleaned up with little machining. .010-.020 is going to make a very small difference and I am sure it probally wouldn't even be noticable. now if it was a high rpm or race motor no way but in a boat i woud do it.
Jesse
Southtowns27
Well Known Member
Just sleeve the bad cylinder, that way the bore stays the same in all 6 holes