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Hey, are we off-topic?

Nah, I think it is still indirectly related to the original topic :tonque:

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Originally Posted by NZConvertible (Post 7541965)

People regurgitate info all the time. Doesn't mean it's right.

Most NA owners don't make nearly enough power to need a radiator upgrade. Capacity-wise the stock one is fine. Even mildly modded turbos (which use exactly the same radiator remember) don't have problems in normal duty. Track work might be a different story though.

The stock radiator is crap because the plastic parts fail at 20-odd years old? Show me plastic radiator parts that don't. Welcome to the real world. Like any other part, if it fails you replace it, and you can expect another 20-odd years of service.

Upgrades aside, the only real advantage an all-aluminium replacement radiator has is that they tend to be cheaper because they're not OEM.

Agreed. The stock radiators are multi-louvered and have a high fin count. They are well made, but after 20 years, the plastic breaks down.

I have heard of many people having cooling problems after installing big aluminum race radiators or all copper replacements.

The big aluminum radiators have such a thick, dense core that they do not get enough airflow with stock ducting/fans.

The copper rads usually have low fin counts and fins that aren't multi-louvered. Cool enough under low loads, but have been seen to creep up to high temps on hard runs.

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Originally Posted by scathcart (Post 7540819)

Aluminum alone, yes. However, it is my understanding that once the aluminum has oxidized, and formed itself a layer of aluminum oxide, which is far less reactive, the zinc becomes the sacrifical anode.

Having examined the slight pitting on an installed zinc anode, it would seem that the theory holds true.

My aluminum outboard engine also uses a zinc anode. Where the paint has been scratched off and bare aluminum has been exposed for years, no corrosion has taken place to the aluminum, while the zinc is badly corroded.

I would like to point out what you already said. "The aluminum has oxidized, and formed itself a layer of aluminum oxide..." This would be the reason that you really don't need a sacrificial anode in the first place. Unlike most steels and irons were the oxide layer cracks open on the surface, aluminum does not. I beleive zinc develops the same type of protective layer also, which is the benefit of galvanizing steel. Many mufflers are aluminized which is a coating of aluminum over the steel.