Aluminium vs Steel rods

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6.50camaro
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Aluminium vs Steel rods

Post by 6.50camaro »

What are the advantages or disadvantages of aluminium vs Steel rods in a drag race only motor 355 sbc? Dan
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Re: Aluminium vs Steel rods

Post by Charliesauto »

There are 0 positives to be gained by using an aluminum rod.
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Re: Aluminium vs Steel rods

Post by BillK »

Charliesauto wrote: Sat Jul 28, 2018 9:52 pm There are 0 positives to be gained by using an aluminum rod.
Then why do people use them ?
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Re: Aluminium vs Steel rods

Post by pdq67 »

I think one reason is that they are more forgiving when used to handle high compression and nitro.

In other words they absorb some of the, "hammer", from combustion that high compression and nitro will throw at an engine. They tend to not beat the rod bearings to death is all.

How far off am I you guys that know more about this than I do??

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Re: Aluminium vs Steel rods

Post by swampbuggy »

Advantages= 1. MAYBE a little lighter, is this an advantage, maybe/maybe not. Depends on just what you are doing with the engine.
2. MAYBE a little cheaper to buy, ???
3. Engine will rev a little quicker IF the rods are indeed lighter, will it make more H.P., "NO".

Dis-advantages= 1.WAAAY shorter service life.
2.More likely to fail at any time.
3. Much more bulky which may mean grinding for clearance is necessary
4.Bearings have to be pinned to retain their location.

There are probably some things i left out. Mark H. :)
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Re: Aluminium vs Steel rods

Post by engineguyBill »

The ONLY advantage to using aluminum rods is to reduce rotating weight, which will result in higher RPM potential in a properly designed maximum-effort race-only engine. The engine must have the right induction system, camshaft timing events, compression ratio and exhaust system in order to reap the benefits of high RPM operation.

Most currently-available aluminum rods have service life comparable to similar high performance steel rods and aluminum rods are not any more prone to failure than compabable steel rods.
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Re: Aluminium vs Steel rods

Post by MadBill »

This article talks about comparable lifespan under approriate conditions and also mentions the 'shock absorbing' aspect of aluminum rods that pdq noted: https://www.dragzine.com/tech-stories/e ... -with-grp/
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Re: Aluminium vs Steel rods

Post by Mark O'Neal »

I used to manufacture aluminum rods. Their principle advantage, at the time, was that they were one third the cost of a steel rod (Small Block). They were the basis for the formulation of Mark's first Law of Racer Economics: "it's easier to come up with $300.00 three times a season than it is $900.00 once."

I don't think I've sold two sets in the past 20 years.
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Re: Aluminium vs Steel rods

Post by Mark O'Neal »

engineguyBill wrote: Sat Jul 28, 2018 11:12 pm The ONLY advantage to using aluminum rods is to reduce rotating weight, which will result in higher RPM potential in a properly designed maximum-effort race-only engine.
Well, you also have the fun of guessing when they are going to flee the relative comfort of your engine block for the freedom of the road......
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Re: Aluminium vs Steel rods

Post by mike hohnstein »

Maintaining steel rods, changing bolts and bushings, magging and keeping both ends round, doesn't cost much more to throw a new set of aluminum rods at the engine every 200 pass's.
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Re: Aluminium vs Steel rods

Post by Charliesauto »

engineguyBill wrote: Sat Jul 28, 2018 11:12 pm The ONLY advantage to using aluminum rods is to reduce rotating weight, which will result in higher RPM potential in a properly designed maximum-effort race-only engine. The engine must have the right induction system, camshaft timing events, compression ratio and exhaust system in order to reap the benefits of high RPM operation.

Most currently-available aluminum rods have service life comparable to similar high performance steel rods and aluminum rods are not any more prone to failure than compabable steel rods.
Explain why a reduction in rotating weight will result in higher rpm potential?
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Re: Aluminium vs Steel rods

Post by hoodeng »

As pdq67 said , alloy rods take some of the hammer out of fuel engines , this is part of the reason they are used in fuel HD engines , the rods are checked regularly for distortion ,but as Mark pointed out they are cheaper so its easier to make a decision to ditch the part if it has been subject to detonation, distortion or its cycles are up.

There is some pretty big stuff flying around inside a 180 inch twin.

The photo is of a set of stock Twin cam HD rods, and a fuel HD rod and piston ,which has been subject to detonation.

Cheers.
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Re: Aluminium vs Steel rods

Post by cab0154 »

I have run some in a 4" stroke shifting around 7800 and saw no advantage in ET or MPH at that level. So I wouldnt even bother unless you are going to be turning one hard enough to need titanium valves.
"Anyone who thinks the low RPM engine will be faster just does not have as much experience as the rest of us" -The late, great Joe Sherman.
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Re: Aluminium vs Steel rods

Post by swampbuggy »

Mark O'Neal at 12:30 am July 29th..... :lol: :lol: :lol: :lol: :lol: Mark H.
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Re: Aluminium vs Steel rods

Post by swampbuggy »

I will betcha NASCAR mandates STEEL con-rods.......and i betcha i know why ! :wink: Mark H.
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