{"id":1179,"date":"2018-01-31T00:01:57","date_gmt":"2018-01-31T04:01:57","guid":{"rendered":"http:\/\/maxtorqueperformance.com\/?p=1179"},"modified":"2018-01-31T00:03:36","modified_gmt":"2018-01-31T04:03:36","slug":"debunking-aluminum-rod-myths","status":"publish","type":"post","link":"https:\/\/maxtorqueperformance.com\/staging\/index.php\/2018\/01\/31\/debunking-aluminum-rod-myths\/","title":{"rendered":"Debunking Aluminum Rod Myths"},"content":{"rendered":"
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By Andrew Wolf<\/a> <\/span> <\/span><\/p>\n

For as long as connecting rod manufacturers the world over have been using blends of aluminum to create lightweight, high performance rods, said pieces have lived under constant scrutiny regarding their long-term durability and usefulness. Even today, as technology has advanced light years beyond what the early aluminum rod manufacturers believed was possible, it continues. And while these concerns may have been warranted decades ago, those in the industry view them as nothing more than common myths these days. And they are myths they\u2019d like to debunk, once and for all.<\/p>\n

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GRP Rods is among the industry leaders in connecting rod technology, and produces a complete line of aluminum rods, including those for Pro Stock, Pro Modified, and HEMI pieces for Top Alcohol and Top Fuel engines.<\/p>\n<\/div>\n

In order to zero in on the tall tales surrounding any discussion of aluminum rods and to help set the story straight, we placed a call to our good friend Brian Scollon at\u00a0GRP Connecting Rods<\/a> \u2013 one of the most respected and successful manufacturers of aluminum rods for the racing and high performance industry. Considering their experience in everything from Top Fuel Dragsters to muscle cars, suffice it to say, they know a thing or two about what an aluminum rod does and doesn\u2019t do.<\/p>\n

Over the years, only a couple of common myths regarding aluminum rods have stood the test of time, and while a \u201ccouple\u201d may not seem like that big a deal of a deal, they strike right to the very core of the usefulness of aluminum for construction of such vital components.<\/p>\n

Aluminum Rods Stretch, You Say?<\/strong><\/p>\n

From web forums to print magazine articles, virtually anywhere that aluminum rods are discussed, you\u2019ll surely find the topic of rod stretch somewhere in the conversation. Or to be more specific, permanent stretching of the rods. It is the most commonly discussed \u201ccon\u201d of choosing aluminum connecting rods for an engine, and according to GRP\u2019s Brian Scollon, is also purely false in this day and age.<\/p>\n

\u201cEveryone out there is under the impression that aluminum rods permanently stretch, but this simply is not the case,\u201d said Scollon. \u201cIf anything, we see that they actually compress. If there\u2019s something going on, be it a hydraulic situation or just simply not enough rod for the power level, they can compress.\u201d In his 17 years entrenched in the connecting rod business at GRP, Scollon adamantly states that not once has he seen an aluminum rods exhibit signs of permanent stretching.<\/p>\n

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The amount of time that you can get out of a rod is completely application-dependent, and people tend to group them all into one.<\/p>\n<\/blockquote>\n<\/div>\n

As every engine builder out there is aware, all connecting rods, regardless of their material or construction, stretch under higher RPM use, and aluminum is certainly no different. Tolerances for such stretch are accounted for and combustion chamber measurements are planned out accordingly depending not only on the material, but the process (billet, forged, cast). As a general rule of thumb, aluminum rods tend to stretch less than .010\u2033 more than a steel rod. Thus, if you\u2019re setting the deck of a Big Block for .050\u2033 total piston to head, you\u2019ll want to provide clearance for .060\u2033 when utilizing aluminum rods. GRP actually tests such occurrences in-house by dropping their rods in boiling oil and measuring the growth.<\/p>\n

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All connecting rods stretch under high RPM use, and aluminum rods will tend to stretch .010\u2033 more than steel with all other variables being the same.<\/p>\n<\/div>\n

This expansion that aluminum rods endure is attributed to the inherent thermal expansion of aluminum as a material more so than high RPM movement. \u201cWe\u2019ve been hearing it for years, and have just never understood where that myth is coming from,\u201d explains Scollon. \u201cSome say that back in the early days with the old rods and some of the other original aluminum rods use to stretch, but they don\u2019t do that anymore.\u201d<\/p>\n

Life Insurance<\/strong><\/p>\n

Another common topic that many folks commonly misstate or underestimate is the overall life of aluminum connecting rods. Sure, on average, aluminum rods tend to carry a slightly shorter life expectancy than steel and other materials, but many out there would have you believe that you\u2019ll be chucking a set of rods in your bracket racing engine every few passes like a nitro car. Scollon insists that this too is simply a misconception.<\/p>\n

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While more extreme applications tend to deliver shorter lifespans on an aluminum rod, milder bracket racing applications can expect hundreds and hundreds of passes out of a set of such rods. This of course is another common and unsubstantiated myth.<\/p>\n<\/div>\n

\u201cThe amount of time that you can get out of a rod is completely application-dependent, and people tend to group them all into one,\u201d says Scollon. \u201cA guy will call us to order rods for a bracket car and someone has told him he can only run an aluminum rod 25 passes before it needs to be replaced. That may be the case in a nitro or blown alcohol car, but in something milder, you can get hundreds and hundreds of passes out of them.\u201d<\/p>\n

What it essentially comes down to (and such is the case with all sorts of components), is selecting a rod that\u2019s built for the combination. Even steel rods, while certainly carrying a longer life expectancy than aluminum, won\u2019t last long if a proper part for the horsepower isn\u2019t chosen.<\/p>\n

In nitro engines, the compressive load placed upon the rods on the top end of the track is extreme to say the least, limiting their use to 8-10 passes at best. Blown alcohol and Pro Stock engines meanwhile, put a different form of extreme stress on the rods thanks to rotations at or above 10,000 RPM. For these racers, however, the performance benefits outweigh the cost and maintenance.<\/p>\n

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Aluminum rods in nitro engines will typically last no more than 8-10 runs, thus the reason for teardowns for inspections or replacements between each pass.<\/p>\n<\/div>\n

But for the weekend warrior bracket racers out there who would be most concerned about connecting rod life, Scollon explains that it\u2019s nothing for a customer to put several hundred to a thousand-plus passes on a set.<\/p>\n

Flexing Their Muscles<\/strong><\/p>\n

Think steel rods are stronger than aluminum? Aluminum rod manufacturers would beg to differ. \u201cThe topic of overall strength is also very application-dependent, but can we build an aluminum rod stronger than a stock steel rod? Absolutely,\u201d Scollon exclaims.<\/p>\n

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