|02-22-2017 10:47 PM|
Seizure = " the action of capturing something using force." Webster ( can be seen with a visual inspection )
Galling = " Galling is a form of wear caused by adhesion between sliding surfaces." Webster ( can be seen with a visual inspection )
These words with definition are used commonly with pistons ( both meaning basically the same thing ) when the side wall of the skirts of the piston loose lubricant , excessive heat or excessive wear removing some of the outer layers of the piston and depositing them in most cases onto the Cyl wall
But here we are talking about
Collapse = " to fall or cave in " Webster
What happens is the skirts of the pistons fall in , get smaller , they dont brake , they dont seize they actually get smaller from when they were new/installed , the skirts still look to the eye perfect in every way , When gaulded or seized the skirts look almost like they were ground on , in most cases dark from the heat and in most cases deposits of aluminum on the Cyl walls
But when your mic the collapsed piston skirts there .003-.008 +/- smaller then they were installed or what the spec sheet was when the pistons were bought new which makes the pistons slap in the bore and causes a knock
The collapsed pistons are still very usable just not in the block that you did the bore for when they were first installed , bore a new block to match the piston size which we do with every engine we machine and the collapsed pistons work perfectly " the major piston shape is still 99.9% solid. " if it was 99.9% solid to start with
Only the piston skirt size changes , the ring area and everything else in most cases stays as good as it was new
" Piston collapse
A reduction in the diameter of the Piston skirt caused by heat and constant impact stresses. " http://www.motorera.com/dictionary/p...iston_Collapse
A good read on how to measure a piston and how pistons can be reduced in size from collapsing
I hope this helps
|02-22-2017 05:35 PM|
They seize to remove the upper high points prevalent at the time it happens, it's called a seizure. 2 strokes can do that all day long, in fact you run them hard if a race engine and then pull pistons out and look for the seizure points to then dress them down and put it back together to run it again. Factory procedure for mechs racing back in the day and even now. I do it all the time.
If you truly have collapsed a piston you won't be running it again, it is no longer dimensionally stable as it has been yielded.............if it were possible think of the possibilities of someone 'rebuilding' pistons. Of course l like Tom I have done it, but I wouldn't call the pistons 'collapsed', they more accurately fit the definition of seized I gave above, the major piston shape is still 99.9% solid.
|02-20-2017 08:53 PM|
Many things will break a piston skirt debris , to much timing , piston to wall clearance , to short or small a piston skirt for what your using them for etc most are from excessive skirt load
I have actually taken 4 pistons that had collapsed the skirts and bored the block to match them and ran them in my Focus for 6 years making north of 300hp to the wheels
|02-20-2017 06:26 PM|
BTW - two definitions of 'collapse' led to the disagreement it appears.
Common definition of physical failure vs. a specific one of reduced diameter from a previous overheating of the piston.
Which definition was meant by the piston company quoted as evidence is questionable, as reinforcement to prevent physical collapse will NOT prevent the reduced diameter situation from overheating.
|02-19-2017 08:58 AM|
|02-19-2017 02:05 AM|
To all concerned, I started this and shouldn't have, pistons CAN collapse................what I should have said was that they commonly don't collapse just a little to rattle a little bit like mentioned early on in this thread, rather, a collapse is a major fail pretty much rendering a part as junk. At least to me.
I apologize for any misleading I did there, it was wrong. I don't do well when trying to out bullsh-t people and that one is on me alone.
|01-20-2017 03:44 PM|
Ahhhh .... right
I have had more then likely 10,000+ sets of Forged pistons go through my shop , I know hands down that the skirts of a piston can collapse
Probe easily could of said breaking , cracking but they chose collapse and yes I am sure they chose that word specifically for there advertisement because it is a known problem and they addressed that specific problem and why its in the advertisement
Email and company that makes Forged pistons or call and ask them if its possible for a Forged piston to collapse with over heating it
Just because you dont know or think its BS doesnt mean it doesnt happen
|01-20-2017 02:23 AM|
|01-19-2017 11:05 PM|
LOL I am not talking about the reinforced
" Reinforced piston skirts to eliminate piston skirt collapse. "
Not the reinforced skirt yes most Forged Piston Companies do that part but Probe specifically used the word collapse not break and Probe is a very well known Forged piston company
If I searched there is talk all over the net from major piston companies about piston skirts collapsing , just because you think its BS doesnt change its a fact that it happens
|01-19-2017 09:22 PM|
|amc49||ALL PISTONS MADE ON THE PLANET have reinforced skirts. All that means is that the piston won't suddenly fail by breaking the skirts out of it.|
|This thread has more than 10 replies. Click here to review the whole thread.|