Repairing piston damage

[91r/t]

So I had some serious **** going through my motor. The block is junk as the scratches are way deeper than I can bore but I think the Pistons are salvageable. The crank, rods, and all the bearing surfaces are untouched but the cylinders seemed to have take the brunt of it. I have no idea what happened as I have not found anything in the filter or oil pan but I recently acquired the car from my buddies estate so I’d like to reuse the parts I can to keep costs down. All the damage seems to be above the piston rings which I know was the least crucial area for sealing. I’m thinking with some really fine paper knocking the high spots off and reusing my forged aluminum pistons. What do you all think ? I have included one piston which was the worst one and a couple of the cylinder walls which are garbage. The block has already been bored .030 over and with a stroker kit I really don’t want to run .060 over plus I’d like to save my $700 Pistons. The skirts have scratches that I cannot feel with my fingernail but the top ones are pretty decent.

 

[coronet68mx]

Did the piston rings break?

 

[oldbee]

Wow, IMHO the only way to reuse pistons is to sleeve the block. Price? 50/50 either way. Fresher block or new pistons; not really up on machining costs.

 

[threewood]

Sleeve the block. Is that the only hole damaged or is that average for the rest as well?

 

[Demonic]

Sleeve it.

 

[91r/t]

No sleeving.....6 of the 8 holes are like that. My buddy has a virgin 1972 std. bore 440 I will grab and bore it .030 again to match my pistons. Rings were all fine and no sharp edges.....had to be metal of some sort. My rockers and shaft were all chewed up, so maybe that went through the cylinder walls? Anyway I am just concerned with reusing pistons due to cost and the fact they are balanced with my assembly. I do not want to run a .060 overbore and chance thin cylinder walls with my 500" stroker kit.....besides these scratches are huge and will not clean up I do not believe anyway. I work in a machine shop and am pretty good at gauging depths or scratches and these are DEEP! I am going to clean the pistons up with 1000 grit then micron paper and go that route I believe.

 

[miller]

I am going to clean the pistons up

You already know, but just to remind...be sure to dig all bits of steel, out of the pistons. Or, you'll look a more scored cylinder walls.

 

[91r/t]

You already know, but just to remind...be sure to dig all bits of steel, out of the pistons. Or, you'll look a more scored cylinder walls.

Yea I am going to soak them in my clean tank after all my sanding and polishing to clean them up nice.

 

[tmaleck]

I feel your pain, but I would say every time I have 'saved' money by reusing or buying inferior parts it has bit me in the ***. After 40+ years, I learned my lesson. Buy what you need in as best a quality grade as makes sense.
Tim

 

[91r/t]

I feel your pain, but I would say every time I have 'saved' money by reusing or buying inferior parts it has bit me in the ***. After 40+ years, I learned my lesson. Buy what you need in as best a quality grade as makes sense.
Tim

Agree 1000%. I didn't build this thing and quite honestly, it has good stuff on it. I think it basically boils down to the wrong combo of parts. I will figure it out and get er back on the road.

 

[68 HEMI GTS]

Tape the ring lands off and use glass bead (low pressure) on the piston skirts. Polish them after with red scotch brite soaked in mineral spirits or wd40. Or you’ll have to dig the metal out with a pick. Glass beading is the better way to go.

 

[91r/t]

Tape the ring lands off and use glass bead (low pressure) on the piston skirts. Polish them after with red scotch brite soaked in mineral spirits or wd40. Or you’ll have to dig the metal out with a pick. Glass beading is the better way to go.

I don't have access to any glass bead blasting, but I can use the red scotch brite on a wheel at low rpm at work.

 

[68 HEMI GTS]

Dig the metal out first. Then Use the scotch brite by hand. Polish the surface with horizontal motion to how the piston travels. I lay a soaked scotch brite in my palm then use the other hand to stroke the piston.

 

[91r/t]

Dig the metal out first. Then Use the scotch brite by hand. Polish the surface with horizontal motion to how the piston travels. I lay a soaked scotch brite in my palm then use the other hand to stroke the piston.

It is an aluminum piston and doesn't look like there is any metal in it....you mean the edges of the scratch and get it "flat" before polishing? Also you mean polish the piston the opp way it travels in the cylinder bore or same direction?

 

[91r/t]

Now I see what you mean....Little bit of steel left in the scratches. I am picking that out with a dental scraper......good thing my sister is a hygienist haha!

 

[wyrmrider]

OK give that block a few strokes with a RIDGID hone and see what happens how many thou to clean up?
no glass beads they are everywhere you should be able to find one
use NEW glass bead
or pick all out as you are doing and sand above the rings
below the rings you want a cross hatch or you can Knurl
Knurl would work also if block cleans up with a few thou extra clearance
there has to be crap all the way though the motor so clean all the hidden spots
did you cut open the filter?

 

[mopar_chuck]

I realize that the block is bad the way it sits but DO NOT throw it out. Big blocks are stating to getting hard to find and lots of people would be happy to re sleeve it if they knew it wasn’t cracked..... including myself. Good luck on the rebuild

 

[68 HEMI GTS]

It is an aluminum piston and doesn't look like there is any metal in it....you mean the edges of the scratch and get it "flat" before polishing? Also you mean polish the piston the opp way it travels in the cylinder bore or same direction?

Oppisite or across the skirt if that makes sense.

 

[BSB67]

You mention building a stroker twice. Is this already a stroker motor? If you are building a stroker, you will not be using those pistons anyways.

Have the block checked. A 0.060 block will be fine. Just have it sonic tested to be sure something odd isn't going on.

New block or new pistons. Either way. But if this is just a beater, I'd consider bore and new pistons. Then you can focus on the 500 motor.

Why did you tear into the motor to begin with?

 

[popslavaz]

Check in to Swain Tech Coatings for coating the skirts on your pistons.I have used them for years for skirt and dome coating with great results.Our Nicom -chrome cylinder walls were tough on pistons.We used Swain Tech coatings saved our expensive top pinned pistons from looking like yours.If they are still round,get them PC9 coated. So slippery oiled can’t hold on to them!!!