In a previous thread; I indicated that I would be pulling my 383 and taking it apart to get all components balanced to eliminate some annoying vibrations.

Hard to tell from pics without actually seeing, and feeling the cylinder walls, but that appears to be the results of piston slap. Can you feel anything in the shiny area, like scratches? OR is it more cosmetic?
Then, I see the circular rings at the upper edge of the bore, right where the rings would ride at the top of piston travel(TDC)...that's not really "normal". I would have the block/cylinders checked before doing anything else...see if the cylinders are good enough to hone, or if they need to be bored to the next larger size. IF the cylinders measure out well, and are not egg-shaped, you can prolly get by with just a good hone job. I would also check the piston size, and make sure the pistons are the correct size of the cylinder bore size...they may be a smidge too large.
 If this is a 400 block, it may not be able to take a larger bore size safely.(but then again, I don't see any steam holes between the cylinders, so it's prolly not a 400..)


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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

I would strongly recommend you follow the thoughts and recomendations of Adam's Apple.

I am with Joel on this one also..do all the cylinders look like this one..or just the one pictured..I can see some hone in the shine area but the flash takes some of the picture away..maybe more pics with less or no flash but other than that can't do much with just one picture..oh are you sure its a 383..now is the time to get it right..you say the pistons are already 30 over..have a machine shop measure everything and see where and what would need replaced..you ask about rings..I have always been a fan of the gap less ones..gets the leak down close to 1%.
Rich

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My first parade at Carlisle 2010

IT would APPEAR to me that this engine does not have many miles on it. No carbon build up on top, and it LOOKS like a recent hone job has been done, with cross hatch lines. Also LOOKS like the rings were never seated correctly. Just my thoughts.

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383's are usually 350 block and 400 crank, if you have to bore to 40 thousands and if not matching numbers I would go with a GM 383/425hp short block and bolt your other stuff back on or go with a long block, much quicker and comes with a 1 yr. or 24 k. 

What is the piston number, it should be stamped into the top or maybe cast into the under side. As said the lack of steam holes makes it more likely to be a 350 block.
The 400 blocks are bulged in the outside walls from the large cylinder bores and some have 3 plugs per side.

http://i80.photobucket.com/albums/j199/64elcamino/block.jpg
http://i80.photobucket.com/albums/j199/64elcamino/400rtsd.jpg

This photo shows the steam holes in the block

http://i80.photobucket.com/albums/j199/64elcamino/77%20Nova%20project/engine/pistons.jpg