With the proliferation of crate engine assemblies and the cultural groupthink surrounding Chevy components, the selection of specific reciprocating parts has become almost an afterthought.
Building a bulletproof small-block? Then hand over the forged crank, rods and pistons, please. Forged is the strongest, right? But what about the forging? As long as it is the right diameter, length or whatever spec the engine calls for, most of us don't question things until those things come apart somewhere around the 1,000-foot mark.
So, it was with great curiosity that we took a look at the new powder metal-forged connecting rods from Howards Racing Components (a manufacturing division of Howards Cams). Produced in partnership with GKN Sinter Metals, a company that manufactures O.E.M. engine components, these new rods promise to redefine the perceived link between "forged steel" and "strength."
The new rods are made from sintered powder metal, a specialized mixture of metallic elements that is pressed and heated to form super-strong, lightweight parts. It's an alloy part, really, and sintering is the heating process that bonds the powdered elements together, but without melting them. (Some elements in the powder mixture are added for their bonding capability.)
The elements of the metal composite mixture, like the Colonel's chicken recipe, are a secret GKN Sinter Metals keeps close to its corporate chest. There's not a single magic formula for all powder metal parts, either; it varies from product to product, with the Howards Racing rods using a mixture different from other parts manufactured by GKN, with the primary component being ASTM 4260 steel.
Strength advantages come in the denser grain of the materials packed into the forging, as well as more uniform weight. Howards tells us that each rod is within just a few grams of the next (the average weight is 585 grams for a 6-inch small-block rod), which makes matching components and balancing an engine easier. The rods are easily resized, too, by simply honing out the big end and inserting readily available oversized bearings.
These are high-end, racing-quality rods designed to withstand extended, high-rpm performance, such as circle track racing. Consequently, they're not the cheapest rods on the market, but surprisingly, they're certainly not out of the reach of the average enthusiast-they run about $600 a set.
Stronger than "pink"
The sintered powder metal connecting rod is a mainstay of almost every auto manufacturer, as this construction method produces very strong and comparatively lightweight parts. The Howards rods also use a "fractured" cap. This means the rod and cap are formed as a single piece and the cap is carefully "split" afterward. The idea is to create a puzzle-piece fit that is ultimately stronger and better sealing than machined/saw-cut rods and caps. Howards specifies premium ARP hardware, including ARP 2000 cap screws. But before you wave off the thought of mere regular-production engines not being up to the performance standards you would expect, the truth is, that compared to old-school rods of the muscle car days, powder metal parts are much stronger. In fact, the powder metal rods in the garden variety 3800 V-6 of your wife's Impala are stronger than the old Chevy "pink" rods. And as for the rods in the new Corvette's LS2 or LS7 engine, well, those much-respected forged steel pink rods are downright brittle in comparison. Howards says their new rods rate a 42 on the HRC hardness scale, with the typical "pink" rod delivering around a rating of 20.
Simply put, these rods are stronger than 4340 forged steel. In fact, Howards says the strength is closer to 300-M, but without the brittleness. That's pretty darn strong, if you ask us. As we finished this story, Howards was just ramping up full production of their Chevy rods, with the first ones offered in a 6-inch length. Other versions are on their way-and likely already available as you're reading this. The rods are made in a Michigan plant, which is close to all the domestic auto manufacturers. We're told they produce about 100,000 connecting rods per day! And as a testament to the durability of powder metal-forged rods, GKN says they have never received a failure complaint of a rod used in an original equipment application. We think that's a good enough reason to try them in your Bow-Tie's performance 350.
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 The assembly process begins...  The assembly process begins in a tumbler where the powdered metal-base material is mixed with several other ingredients that add strength and other necessary properties to the forging formula. The mixture has roughly the consistency of flour. |
 Prior to hot forging and sintering,...  Prior to hot forging and sintering, the powder metal material is first compacting into the rough shape of the connecting rod. This form is known as a briquette. |
 After being pressed into the...  After being pressed into the general shaped of the rod, the fragile piece is hot forged to give it more accurate shape and detail. |
 Here's a look at a forged...  Here's a look at a forged rod, which definitely has the right shape, but it hasn't been hardened through sintering. |
 Sintering fuses the powder...  Sintering fuses the powder elements of the part into a solid piece. This is done by heating the forging to just below the melting point of the primary metal ingredient. The process solidifies the part and greatly reduces porosity. |
 Here's a look at the finished...  Here's a look at the finished part. Note that the rod and main bearing cap are formed as a single part. They are separated during another step in the manufacturing process. |
 The rod and cap are one piece...  The rod and cap are one piece during the forging and sintering processes, but are separated--or fractured --to produce a more precise seal. The rough surfaces fit together perfectly in only one way: the way they were split. |
 Here's a look at a fractured...  Here's a look at a fractured cap (top) and a conventional, saw-cut cap (bottom). The fractured cap has the advantage of grip, as the textured surfaces provide almost a Velcro-like quality. |
 Here's a look at the three...  Here's a look at the three primary manufacturing stages of Howards Cams' new rods: a pressed briquette of powder metal alloy (left), a hot forged part and a finished, sintered component middle. Note the hardware, too, on the finished piece; it's from ARP. |