How to tell a Scratch from a Crack in a Cylinder?

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eekvonzipper

eekvonzipper

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All Clean, Ready to Assemble. Did a Final Hone with a Flex-Hone
and Saw This Line at the Bottom of Cyl 6... (on a 273)
It is Perfectly Straight, up/down.
Ran the Stone-Hone thru it One-More-Time and it was Still There!
I can't feel it... but I don't have fingernails (just nubs)
The Flex-Hone cleans up the lines left by the Bore Gauge but not This Line.
How do I know if I should just Stop? I tried to do a Budget Build at Home w/ No Machining...

scratch.jpg


scratch2.jpg
 
I also think it is a scratch, two reasons. You can see in the close up another line next to the main line. Both lines are dead straight which would be extremely unlikely from a crack, which you would expect to have a jagged/wobbly line.
 
I say it's a scratch too.

You could have the block magnafluxed.

Might be cheap enough at a machine shop, I assume the block is empty at this point.

If it were a crack it would have some signs on the surface that is 90 degrees to it (top in the photo)

Plus cracks are not that clean they follow the grain of the metal.

Plus the second mark to the left (in the closeup photo)

If it really bothers you you could bore the cylinders but then your budget would increase by a few thousand dollars for oversized pistons, and machine work.
 
IMO, Looks like a scratch since it's so straight. This looks like a particle was dragged up and down the bore and it's filled up with carbon.
A fresh scratch, even with depth to it, should tend to reflect light.
Magnafluxing may show a deep scratch as indication, as the iron powder will bridge the gap.
 
Looks like a scratch to me.
Magnaflux would most likely show an "indication" because the magnetic lines of flux would obviously be disrupted there so I'm not sure that would tell you anything...just scare you. Dye penetrant would indicate if there is any depth to it beyond what you could see due to the fact it would get sucked out of the depths of the crack if there was one, when you apply the developer.
 
I agree it looks like a scratch, but what made it that deep in the bore? i suppose a skirt could do it. Any chance you have the piston that came out of that cyl? Any debris down that low would have to come from the crankcase, right :)
 
That scratch was made because whoever honed it left the stones too far out when they pulled the hone out of the bore and it scratched it on the way out. Unless you can feel it with your fingernail, I wouldn't worry with it.....but I would run a dingleberry in it and clear it up.
 
OldmanRick said:
I agree it looks like a scratch, but what made it that deep in the bore? i suppose a skirt could do it. Any chance you have the piston that came out of that cyl? Any debris down that low would have to come from the crankcase, right :)
Click to expand...
Here's That Piston (Untouched, as it came out)
and the Line as seen from the top...
It's 3 1/2" down from the top So, it's Under the Rings.
I didn't do that Honing it... It had a (Very Bad) Previous Rebuild. Sorta. The Ring Gaps were All Waaay Too Big and it Smoked, Alot.

p1.jpg


p2.jpg


l1.jpg
 
Shiny areas on the pistons are fairly normal. The scratches all across look some trashy oil was run thru it at some point. That said, i think you're good to go. :thumbsup:
 
RustyRatRod said:
That scratch was made because whoever honed it left the stones too far out when they pulled the hone out of the bore and it scratched it on the way out. Unless you can feel it with your fingernail, I wouldn't worry with it.....but I would run a dingleberry in it and clear it up.
Click to expand...
I found an old Pic of that No.#6 Hole from the Teardown last November... The Line was there already when I tore it down.
I think that's why I was worried that it might be a Crack.

l2.jpg
 
In your pic in the first post, that's a freshly honed cylinder. That's what I was basing my guess off of. Also in the picture above, it appears the scratch does not go as far up the cylinder as in the first picture, leading me to think it's not the same scratch. But whatever. If you're happy with it, send it.
 
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