Alumunum Rods In A Street Engine ?
 

I came across a side oiler with Michael Giannone aluminum rods.

Cool for a light weight racing engine, but how would they be on the street, any problems and why ?

I guess this is one big reason unless you live in Ca., Fl. etc. Where your car is driven all year.


"Do not leave the fasteners torqued for a period greater than 6 months if the connecting rods will be sitting in a box on a shelf or installed in an engine if the engine is going to sit without use. It is good practice to remove all torque and therefore tension and load from the fasteners to avoid housing bore distortion and to avoid over stretching the fasteners beyond yield strength".

they need to be changed frequently, no bueno for the street

Aluminum is a poor metal choice for rods. It is light and if money doesn't matter they make a great race engine that can rev quickly. However you need to replace them often.

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. The rods are likely the highest stressed part in an engine. It is a great metal for polishing. It is easy to machine. It is light weight. It is a superb conductor of heat. It is reasonably corrosion resistant. It is inexpensive compared to other light weight materials, such as Titanium (which is much stronger and lighter). However it has a large linear coefficient of thermal expansion (it grows a bunch when it gets warmer). That makes pistons get closer to the head, when the engine warms up. It creeps under high stress. Those nice round bearings do not stay that way very long.

With todays quality metals, why would a guy use aluminum rods, even drag cars ?

Because they're cheaper than titanium, and in a race engine that's being pulled apart (or blown apart) every few meets they become an option for some.

We have come a very long way from the beginnings of aluminum rods which were originally sawed and shaped from aluminum plate. Those kinds of rods I might not trust.

There are aluminum rods manufactured today that may be run reliably in the typical street-driven performance engine for literally tens of thousands of miles (or more) without any issues. Indeed, aluminum is a different animal than steel, and so the builder needs to understand the intimacies/idiosyncrasies of each rod material and build accordingly.

The short simplified answer: Yes, a connecting rod capable of sustaining several thousand horsepower (for a short period of time) may be run successfully in an engine generating just several hundred (for a longer period of time).

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.

Addendum To My Post #7 Above:
 

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

___________________________


"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

Bill Miller Home Page

The real issue with aluminum wiring is oxidation. Speaking from the owner of a mid '60s home with an unfortunate amount of the crap.

Interesting read. Thanks for the link. A sale of $500 to $750 per set right now. Lower than I would have guessed. These over stock sales, where you can save because someone else canceled their order, are often a snake oil salesman trick and not genuine.

Well on the one hand, I know metallurgy has come a long way over the last 40 years. I also know that one set of data is not enough to state anything for certain.

On the other hand, I do recall books written way back in the day, stating that aluminum rods would not hold up long on the street. They were great for racing where you pull them down and check them frequently, but not for the street. Now this may have been all wrong, but I believe there was something to it. To say "I don't know how the myth got started" might be a little disingenuous and a sales pitch. I have been around long enough to know that people who have a financial interest to sell you something are not always the best source of information.

So have I been passing on an old wives tail that is patently false? Was it once true, but things have changed? Are the manufactures of aluminum rods trying to sell them and conveniently leaving out some things? I do not know.

Assuming they hold up perfectly well, and knowing that the cost is reasonable, why would I want to run aluminum rods? Lighter weight is the only benefit I can think of. The thermal expansion thing is real. Aluminum is 13.1 x 10^-6 verses 7.0 x 10^-6 for steel. A 6.0" aluminum rod a 50 F will be 6.012" at 200 F where a steel rod would be 6.006" at the same temps. It might make sense in a all aluminum engine though.

Well this article talks a bit about the past and that some of the wives tales may have been true back then, and some maybe not. Certainly things are different now.

Anyone interested? Here is the link.
Debunking Aluminum Rod Myths With GRP - Dragzine

Maybe my view in the past was rooted in a lot of half truths, at best, when it comes to aluminum rods.

In industrial experience, I have seen aluminum fail, when the wrong grade was used and the correct grade last. A half million dollar machine failed catastrophically in 6 months use. The correct grade aluminum has lasted 30 yrs now and still going strong.

That said thanks to Paul for opening my eyes on aluminum rods. I'm not sure I would ever choose them in a street engine, because I tend to be conservative. I do not like to rev past 6000 rpm and 7000 is tops for me. The lighter rotating assembly seems to me to pay off more at high rpm and that is just not me. However light rotating assembly can rev quicker, so I wouldn't totally rule them out.

I'm not sure they had NoOx back in the 60's. It is a tube of a grease like stuff that help reduce the oxidation. If your wires do not have that on them, you should put it on.

Bottom line, no electrician I ever talked to likes aluminum wire. It was cheaper than copper. It is not as good a conductor as coper. Other than cost, it has no advantage for electrical wire use.

In the 60's we had some very smart people explain why drag cars could not exceed 160 in the quartermile. They had some very impressive math to back up their representation. Today many cars exceed 160 in the quarter mile. Lots of math doesn't prove anything in the real world if you do not understand the basic underlying physical phenomena you are attempting to model.

Bill Miller is absolutely correct in his comments about street usage. Additionally there are no Funny Car or T/F engines that use anything but aluminum rods today for a very important reason and it isn't weight, it is strength! The beam bending strength of an aluminum rod dwarfs any other rod.

In the FWIW bucket for those who think Titanium is lighter than Aluminum, the density of Titanium is 4.5g/cc and the density of Aluminum is 2.7g/cc. The use of a four function calculator will show that Aluminum is 60% the weight of Titanium or said another way Titanium is almost twice as heavy as Aluminum.


Ed

specific gravity listed in engineering toolbox is
aluminum 2.7
steel ----- 7.8
titanium 4.5

Tensile Modulus - Young's Modulus or Modulus of Elasticity - is a measure of stiffness of an elastic material. It is used to describe the elastic properties of objects like wires, rods or columns when they are stretched or compressed.

Yield strength (you have bent it past the point it will spring back to it original shape).
aluminum 95
steel ----- 345
titanium 730

So we have been loose with terms. Aluminum is not stronger than steel. Steel is stronger, but much heavier. When both materials are made to the same strength level, aluminum is lighter but must be bigger to achieve that. So pound for pound aluminum is stronger than steel. Now fuzzily, I remember, something about, even though two beams , one aluminum the other steel, is at the same yield strength, the aluminum beam will flex more at a given load than the steel beam. I believe the engineer told me that if deflection is the critical factor steel is better.

Titanium is stronger than steel (about twice) and half the weight. It is twice as heavy as aluminum, but 7 times stronger. Lb for lb, titanium is stronger than steel and totally blows aluminum out of the water. The US government didn't spend millions of dollars building aircraft out of titanium in stead of the much cheaper aluminum because they wanted to waste money. It has its advantages.

There are many other factors that must be considered. The experts are saying that because aluminum is more flexible than steel, it can act like a shock absorber in certain critical extreme condition for engine rods, which allow it to not fail where steel rods would fail. I expect kind of like a building too strong to flex will not withstand an earth quake where a less strong, more flexible, building will stand.

Here's the ad. The rods are in a 1966 side oiler, 438ci.

Any idea how much the rods alone cost ?

https://m.facebook.com/permalink.php...84180784988138

Probably faster to just contact the manufacturer directly yourself.

MGP | High Performance Aluminum Connecting Rods - About

Although I did not mention steel, your point and data appear to be the same as I had indicated — and I agree with both.



Although I did not address this attribute your representation is again correct.



The explanation is correct but the actual numbers are alloy dependent and the high strength super steels vastly outperform the best aluminum and or titanium alloys.



This engineer may have been related to the engineers that determined factually and absolutely that 160 mph was the highest speed attainable by wheel driven vehicles in a quarter mile.

When we play fast and loose with this type of information it is possible to send the uninitiated or uninformed down a painful and potentially destructive path. It is not fair to them. They have a right to know the facts and if they choose poorly then, they are big boys and that is their choice.

Connecting rod beam deflection is the #1 connecting rod issue in supercharged alcohol and/or nitromethane fueled engines. A deflection in any given power cycle is followed by mechanical failure in the next. The resistance to beam deflection because of the beam section / girth of the forged aluminum rod is what makes it the universal choice for these high powered large displacement methanol and nitro fueled engines.



This is again alloy dependent. It possible to find low grade steels that are not as strong as high grade titanium alloys. However when you are looking for the ultimate strength and toughness, like for example in a crankshaft, you will find no titanium cranks at any price in blown alcohol or nitromethane engines — because they are not as strong or durable.

You will find ultra pure electric arc vacuum remelt 4340 steels that carry various marketing names like Kryptonite®, M300 etc. The absolute strongest steel currently used for these cranks is the Timken® 4330V alloy steel which will almost but not quite double the service life of the best 4340 steels.




The compressive strength qualities and relative cushioning effect that aluminum rods provide is important if you detonate the engine. Absent the detonation this quality brings no real benefits to the table.

Experts tend to be a dime a dozen with the occasional sale for even less. I have never met an expert that actually ran the rod materials he promoted as being the best, in these types of engines. Bill Miller is the current exception to that rule. It costs a lot of money when you experience a failure in one of these engines and the so called experts want no part of that risk.

Interestingly the alcohol and fuel racers all use high strength super steels for their cranks and high strength aluminum alloys for their rods. Sometimes the rods are forged sometimes billet plate. Most often they are forged and they tend to be Miller's. In general the forgings provide better strength, toughness and service life and the billet pieces provide greater ability to be tailored to special dimensions and or applications.


Ed

I'm not sure they had NoOx back in the 60's. It is a tube of a grease like stuff that help reduce the oxidation. If your wires do not have that on them, you should put it on.

Yup, been over every outlet and light switch in the house with the stuff.

Maybe try looking into Lentz rods? They are very good. I have them in my car.