I have a good running aluminium slant six in my car and understand that these engines were subject to corrosion. What can I do to prevent this.

When I used to built 747's (ok, helped built them) every surface was painted or sealed with a primer. I would assume this would be true with an aluminum block (on the outside). The oil will take care of the inside and for the water jackets, anti freeze has corrosion inhibiters that help prevent, well, corrosion. Of course, you also have cast iron sleaves in the block, so I don't know what can be done about electrolysis between dissimilar metal.

Pull it out and put it away! A running aluminum slant is a rare find. But if you must run it, make sure you keep that cooling system flushed! Does anyone know what those pellets that Cadillac had for their engines (the 4100 comes to mind) are made of?? that series of engine has gained a bad reputation but I have had friends that have had good luck with them .They have told me that the secret is putting 3 pellets that you have to get from Cadillac in the rad once a year to keep the dissimilar metals from reacting with each other/corroding themselves to death. I'm guessing its sort of like the barges/large ships do when they hang blocks of zinc on their hulls to be sacrificed to keep the ship from rusting thru in salt water. (electrolysis)

Found a couple of articles:
http://www.autosite.com/garage/encyclop/ency01e.asp
http://www.auto-repair-guy.com/repairgu ... olant.html

NEVER EVER use tap water. Get good distilled water (or deionized if you can get it). Use good quality antifreeze.

Also, never us tap water to top off a battery. The ions and sediments in tap water will corrode your engine/radiator, and contaminate your battery.

Your neighborhood chemist,

Lou

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Home of Slant6-powered fun machines since 1988

Do not use any pellets of any kind in your cooling system.
Do not use 100% antifreeze.
Do not feel you have to pull the engine and put it on a shelf somewhere.
Do not panic.

The aluminum 225s were indeed subject to corrosion because they were introduced at a time when antifreeze formulations were primitive and scarcely anyone used them (or if they did, they only used them in winter), running plain water in the cooling system instead.

Modern coolant formulations are VASTLY improved in their ability to prevent electrolytic corrosion, if you will choose and use them correctly. "Correctly" in this case means use G-O5 coolant in a 50/50 ratio with clean water. Proof is here:

Part 1:
http://www.caranddriver.com/article.asp ... e_number=1

Part 2:
http://www.caranddriver.com/article.asp ... e_number=1

G-O5 coolant is now readily available at any well-stocked parts store in, I believe, the Zerex brand.

DON'T be tempted to use Dex-Cool! It will rapidly cause corrosion in your radiator, heater core and possibly even more critical parts.

Also make sure that your battery negative cable is sufficiently large (I use 2-gauge cables) and is well-secured to a clean part of the block.

-DS (ran two aluminum 225s in daily service in Denver for a decade, never a coolant-related problem until I foolishly used Dex-Cool in the '62, which resulted in needing a radiator recore and a new heater core).[/url]

I have also run Aluminium Block Slants without any problems and as Dan states, keeping the cooling system in excellent condition is a key to success.

I also go through extra efforts to properly ground the electrical system.
I run a longer ground cable from the "-" battery post down to one of the starter motor's mounting bolts. I also run ground straps directly to the radiator and to the alternator. Basically I want to run the ground "return" current directly to the battery through cables and not through the Alm.engine block to help reduce the chance of electrolysis.
DD