Piston Corrosion

RobE · Dec 9, 2018

Just picked up a 68 440 block with a set of "unused" pistons, however they have some minor corrosion mostly on the combustion surface but some has drifted down to the sides and appears to stop at the first ring groove. I'm not sure how or if I should proceed with these parts.
scotch brite? soda blast? or maybe just some soap and water followed up with assembly lube.
Any help is appreciated.

miller · Dec 9, 2018

RobE said:
scotch brite?

I would use one of the 'fine' grades of scotchbrite, to re-polish them. Be sure to make a wipe in the ring grooves, too.
Whoever put it all together, appears it was done dry...so the corrosion. Hopefully, it was caught in time, maybe they will clean up.

If there's any question about the moly coating on the sidewalls, don't worry about it. It doesn't last that long, anyway.

66Satellite47 · Dec 9, 2018

Scotchbrite works really well. Maybe use a little WD 40 on the Scotchbrite pad. I use the commercial green all the time. I would not worry about moly on sidewalls, I don't recall any coating on any of my pistons. A little scuff above the top ring sure wouldn't bother me, carbon fills micro scratches up.

miller · Dec 9, 2018

Piston on the left, far left side, up top...is that a big nick?

69roadr · Dec 9, 2018

WD-40 and fine steel wool

Demonic · Dec 9, 2018

miller said:
Piston on the left, far left side, up top...is that a big nick?

Some aftermarket pistons have locating notches, similar to factory ones. They indicate direction. That's what it looks like to me.

BSB67 · Dec 9, 2018

I clean this up several years ago in an attempt to sell these fine, rare, and apparently worthless 0.030 over, forged, 68-69 440 piston set.

I was pleased on how it turned out, but now don't remember exactly what I did. But I'm pretty sure it included the use of stainless or brass wire detail brushes with WD40 and compound, followed by short bristle tooth brush and some compound to clean up in the tiny divets left from the corrosion.

fratzog lover · Dec 9, 2018

Spray them with WD 40 and wipe them off so you can see what your looking at. Yes , it looks worse than it probably is now. If you have access to a polishing wheel (or have a HF 3 inch unit for a cordless drill) do a quick rotation over the ring area to expose any deep scratches or nicks.

RobE · Dec 9, 2018

Thanks for all the replies! The notch is intended to be there. I have a pretty good idea of what to do next.
WD 40 then inspect and then tooth brush and some gentle cleaner Non Abrasive.

zyzzyx · Dec 9, 2018

I use Simple Green concentrate on aluminum before I tig weld to clean all the oxidation off.
bare aluminum starts to oxidize right away, so if it sits for more than a day or two, it must
be cleaned. Fine scotch brite and some Simple Green should do the trick!

Piston Corrosion

RobE

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miller

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66Satellite47

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miller

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69roadr

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Demonic

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BSB67

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fratzog lover

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RobE

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zyzzyx

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