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aluminum residue

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Today was a bad day:( I man I had hired to work in the machine shop was making a mistake that could have been if not caught costly. Many of us have broken rods or had pistons seize but I have found that at least in my shop one person in particular was polishing the residue and letting it go on engine rebuilds "arhggg!" So having to retrain him on the basics of engines I began to help him understand that the aluminum was softer then the steel cylinders and the crankshafts, so the light silver that was being polished and left behind would someday if not immediately cost the engine another rebuild as it could cause premature engine wear on the new parts. here is what we usually practice in the shop for this problem hope it helps some of you to have better success in your engine building practices. If the piston or rod has seized and smeared aluminum on the cylinder or crank you will need to remove it before you measure it. You can do this with Mauriac acid. Just take a medicine dropper and put just a few drops on the aluminum that has been smeared on the part. The acid will eat the aluminum but will not hurt the steel. DO NOT GET THE ACID ON YOU . If you do get it on yourself, water and baking soda will get it off. Also don't get it on any aluminum unless you want that aluminum eaten up ! You can get Mauriac Acid at any home improvement store. They sell it buy the gallon, which will do about a years worth of cleanup. Some people use emery cloth or paper to clean aluminum off the parts but that also takes the metal (steel) in the course of removal. after clean up, a mild soda water cleaning will stop the reactions and prep the part for machining if needing. we tend to polish the cranks and hone the cylinders in our rebuild procedures but if the cylinder and crankshaft are within specification we proceed with the rebuild. Something to remember, if you are working on an Old Engine and are having trouble finding a piston. As long as the wrist pin diameter is the same and you can bore the cylinder to fit it. Almost any piston will work. You might have to cut the piston skirt down or have to lathe the piston head to fit the combustion chamber or grind inside the skirt to make it the right weight, but with some imagination you can make it fit and it will work,there is no such thing as NLA pistons because of this practice. we fit the bore to the piston as long as it is within a .30 over spec.

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