Alumunum Rods In A Street Engine ?

[Paul Kane]

Originally Posted by olddog

Aluminum has a nasty habit of creeping. It is used commonly for electrical entrance service in houses. When you torque the wires down in the lugs, you need to do it right once. The connection will loosen over time as the aluminum flows out from under the lug. If you check the lug a few months later they will not be tight, but you do not want to keep tightening them up or you will eventually cut the wire in two.

The point is aluminum does not hold its shape in high stress applications.

This may be the case for electrical lugs for home power, but it is a poor and unfair comparison (and not even an analogy) for con rods. It's pretty safe to say that aluminum electrical lugs are not made of 7075 aluminum. Nor would the aluminum lugs be heat treated to T6 hardness. Etcetera, etcetera, etcetera.

[olddog]

Originally Posted by Paul Kane

This may be the case for electrical lugs for home power, but it is a poor and unfair comparison (and not even an analogy) for con rods. It's pretty safe to say that aluminum electrical lugs are not made of 7075 aluminum. Nor would the aluminum lugs be heat treated to T6 hardness. Etcetera, etcetera, etcetera.

Yes Paul, you are absolutely correct. Aluminum wire is a poor comparison to the higher grades of aluminum available. I only used this to illustrate what creep is. I should have pointed out that rods would be made of a much better grade. My bad.

However even the best grades of aluminum will not hold up in an engine, like steel does.

You did make an interesting point. If you put aluminum rods in a street engine that made little power and let grandma drive it nice and easy, they would last the life of the engine. No doubt in my mind that if you stay under some rpm (stress level) they will last forever.

I only knew of one person to run aluminum rods in a small block chevy on the street. That was 30 yrs ago. I think he got about 10,000 miles out of them. I cannot remember which end failed. I'm thinking it was the wrist pin knocking, but I just do not remember for sure. This memory thing bums me out.

[Paul Kane]

Originally Posted by olddog

You did make an interesting point. If you put aluminum rods in a street engine that made little power and let grandma drive it nice and easy, they would last the life of the engine.

I did not say, "grandma," I did say, "street-driven performance engine."

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"In a hot street application, using the aluminum rod is a no brainer," BME President, Bill Miller, said in an interview with an automotive magazine. "I don't know how the myth that aluminum rods can't be used on the street got started, but I'll guess that, back in the 60s and early-70s, they weren't making them using the process we're using today. With the material we've got and they way we manufacture the connecting rods, they'll live a couple hundred thousand miles on the street because a street application is, for the most part, low load. Our basic Aluminum Rod is made for an 1000-hp, 10,000 rpm race engine. The design criteria for the connecting rod is way overkill for what it's going see on the street. We been running aluminum rods on the street for more than two decades."

~Bill Miller

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