It really wasn’t that long ago that you could pop down to your closest wrecking yard, pull an engine, do a basic re-ring, and slap it back together, because the available cores were mostly clean and rust-free. These days, if you’re still looking at classic muscle-car mills, you’re more likely to have to drag the thing out from behind some guy’s shed where it’s been sitting in the rain for 15 years, all while fighting off the raccoon who lives on the intake manifold. If you don’t want to do a full machine-shop work-up, you’re going to need a magic trick so you don’t end up putting together a block clogged solid with iron oxide.
Introducing electrolysis. It’s the enemy of your aluminum parts when electricity flows through the water in your cooling system and eats your expensive radiator, but it can be your best friend in rust removal. All it takes is a big tub of water, a sacrificial piece of steel, a battery charger, and water softener (sodium carbonate).
Clean your rusty engine and dump it in the bath. Negative lead goes on the part to clean, the Positive goes on the sacrificial iron (do not use stainless steel, it releases poison in the water). Turn the charger on, and let it soak. The electricity flowing through the solution breaks the bonds of the iron and oxygen (rust), and the block gets clean while the anode gets rusty. Don’t panic about the electricity, this is a low-current DC situation. But do this outside; the breaking bonds release hydrogen gas, and it would be a shame to blow up your shop. Check the block regularly and swap out the anode as needed. Then pressure-wash the engine, oil it up, and finish your cheapie rebuild. Thanks, science!
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