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Component Weight
In the "Tech Tip" arena we attempt to address information of concern and enlightenment. In an effort to follow that lead, this bit of information will relate very generally to the recent aggressive efforts toward lighter components within the racing and high performance engines of today.

Carrillo has developed a reputation as a supplier of high quality and extraordinarily durable connecting rods to virtually all facets of the racing community. With this enviable reputation comes the assumption that our parts are "overbuilt" for the applications. This is often illustrated by the fact that a used set of Carrillo connecting rods generates top dollar at swap meets. This certainly may be true to some degree as we have always swayed to the conservative side when supplying parts to the general racing environment. The engineering incorporated in these parts has been basic in nature. Our intention is to supply a part that IS NOT the "weak link" of the system. If the rotating/reciprocating components within the engine were to be taxed beyond their capabilities, the Carrillo connecting rod was not to be the first part to fail. These design criteria may be faulted, but we still maintain it as valid.

As other associated components, pistons, wrist pins, crankshafts have been lightened, so have our parts. Unfortunately, connecting rods are not a significant contributor to performance enhancements. They simply absorb and distribute to the power generated within the system. If the power (loads, not horsepower) is reduced within the system, the strength capability requirements of the connecting rod are reduced as well. In very empirical terms, a piston pin assembly in the area of 700 grams total at 3.800 inches stroke and a 525-gram assembly with a 3.200 stroke do not require the same design connecting rod and crankshaft assembly. Arguably, one could attempt to assign power levels to the design, but alternatively, Carrillo clearly and confidently presents the fact that at a particular weight level, the Carrillo connecting rod is unsurpassed relative to its durability.

In an effort to address the advantages of weight conservation, it must be noted that weight and friction are the enemies of power production. These two elements are considered parasitic losses within the engine. Since we are addressing weight at this time, note that the most detriment is generated in an attempt to accelerate the weight. The effort to sustain the inertia of a rotating mass is significantly less that that effort to accelerate it. Relative to a connecting rod, there are two very critical masses to consider, often not addressed in advertising and promotion. Rotating mass is that weight rotating around the centerline of the crankshaft at half the distance of the stroke of the engine. Far more critical is the reciprocating mass that in conjunction with the piston/pin assembly must move down the cylinder, stop, start, move up the cylinder, stop again and proceed once again down the cylinder. This action incorporates acceleration from stop and deceleration to stop. One does not have to consider this process very long to realize which is most effectual.

Now that the seed is planted that all engine designers and builders have decided to employ nothing but "light" components, lets address the negative side.

Most experienced and credible engine builders have suffered a component failure. Often this failure has been attributed to an inadequate component. Often the component was adequate for an application, just not the one it was subjected to. If you use a piston that is too light for the application, it often cracks due to movement and or annealing. If you employ a pin with a wall thickness too thin for its environment, it may break the rod, damage the piston or spin the bush as well as perhaps fail the pin. Certainly, if the connecting rod is too light, the housing bore distorts, fails a bearing or the blade it compromised by excessive tension load. The point is very simple, as an engine builder, be aware of the component's limitations. There is a very thin balance between weight and durability.

As an example, Carrillo Industries have supplied connecting rods for Ford, Chevrolet and Chrysler contemporary V-8 applications that have ranged from 690 grams total to as little as 465 grams total all for 350/358 cubic inch normally aspirated engines. These parts have all been manufactured from Carrilloy (our steel)!

Regards,
Fred Carrillo and Jack Sparks
CARRILLO INDUSTRIES