Junk Pistons
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Junk Pistons
I have just received these hyper-eutectic pistons for a near enough to stock SBC build.
Considering this part of the piston between the ring grooves will never touch the cylinder walls, would you use them?
Considering this part of the piston between the ring grooves will never touch the cylinder walls, would you use them?
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Re: Junk Pistons
JUNK
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Re: Junk Pistons
Is it on all of the pistons or just one?
This is the reason I ask.
This is the reason I ask.
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Re: Junk Pistons
X2!DCal wrote:I can't wait to hear the logic on this one!
I guess it's easier to just add a note (disclaimer) to the instructions than to fix it.
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Re: Junk Pistons
How is that piston "junk"? Most pistons have exactly the same machining marks what does that hurt?
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Re: Junk Pistons
I've used that piston many times in stock marine rebuilds. I'm not seeing the problem.
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Re: Junk Pistons
Pistons have had those marks for years. I think the machining term is "catheading"? No idea what it is but I was concerned when I first saw it too.
"do it right or do it right away"
http://www.motionmachineinc.com/
https://www.youtube.com/watch?v=ZgIZbveknDs
http://www.motionmachineinc.com/
https://www.youtube.com/watch?v=ZgIZbveknDs
Re: Junk Pistons
[quote="DaveMcLain"]How is that piston "junk"? Most pistons have exactly the same machining marks what does that hurt?[/quote
It may be OK but I'm betting its part of the Skirt Cam turning operation and if so it shows a concentricity issue between the ring grooves, the lands and the skirt. You want those within a thou. if possible. The skirt being machined off center to the grooves is not good.
It may be OK but I'm betting its part of the Skirt Cam turning operation and if so it shows a concentricity issue between the ring grooves, the lands and the skirt. You want those within a thou. if possible. The skirt being machined off center to the grooves is not good.
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Re: Junk Pistons
I wish my brain would retain more important things, and forget less significant things like "catheading". Here's a link that explains it all in detail. https://www.google.com/patents/US4612833
According to the patent dates, this process, "Diamond turning machine for forming pistons of elliptical shape" was first used in 1938! Basically the piston is held stationary as the skirt is machined. Today's version of "cam ground" I guess.
According to the patent dates, this process, "Diamond turning machine for forming pistons of elliptical shape" was first used in 1938! Basically the piston is held stationary as the skirt is machined. Today's version of "cam ground" I guess.
"do it right or do it right away"
http://www.motionmachineinc.com/
https://www.youtube.com/watch?v=ZgIZbveknDs
http://www.motionmachineinc.com/
https://www.youtube.com/watch?v=ZgIZbveknDs
Re: Junk Pistons
Its not to say these pistons will not be ok for the application, but you have to admit, these are not a good example of quality control. My guess is you paid under a $100 dollars for the set. Curious as to where they were manufactured. Piston Guy must be cringing at this thread. Phil D.
Re: Junk Pistons
The 2nd reply to my initial post will give you some indication of where they came from.
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Re: Junk Pistons
I have several new sets at the shop now with the same marks on them and have installed who knows how many in the past with no problems.
For a stock type replacement or a mild performance piston there will be no problems at all with them.
This is a copy and paste directly out of the new silvolite catalogue.
Silv-O-Lite has been diamond finishing piston skirts for over 25 years .
Silv-O-Lite’s diamond finishing is not a lathe or grinding operation . This unique process actually holds the piston stationary while spinning the cutting tool around the perimeter of the piston . In one simultaneous action ellipse, taper, & barrel are cut . One trade mark of the diamond finishing process is a small half moon cut that may show
up on the second land . If this mark is not present, it is because the piston requires less ellipse or has smaller land diameter . even without this identification you can be assured that all Silv-O-Lite pistons are finished with this proprietary process .
This is one that will be going in an engine in a few days.
Andy
For a stock type replacement or a mild performance piston there will be no problems at all with them.
This is a copy and paste directly out of the new silvolite catalogue.
Silv-O-Lite has been diamond finishing piston skirts for over 25 years .
Silv-O-Lite’s diamond finishing is not a lathe or grinding operation . This unique process actually holds the piston stationary while spinning the cutting tool around the perimeter of the piston . In one simultaneous action ellipse, taper, & barrel are cut . One trade mark of the diamond finishing process is a small half moon cut that may show
up on the second land . If this mark is not present, it is because the piston requires less ellipse or has smaller land diameter . even without this identification you can be assured that all Silv-O-Lite pistons are finished with this proprietary process .
This is one that will be going in an engine in a few days.
Andy
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