Frequently Asked Questions - Rods

Each connecting rod is Rockwell tested to validate the heat treat procedure. The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload.

Magnetic Particle Testing, also referred to as MPI Testing and Magnaflux Testing, helps identify surface flaws in metal products that can be magnetized. We use MPI testing to help identify cracks, laps and seams in our forgings during and after production.

All CP-Carrillo Steel connecting rods are manufactured from an oversized forging resulting in the proper grainflow as well as the surface removal of any potential inclusions or surface conversions generated by the forging process. By insuring proper grain flow with our proprietary material, the strength and durability of each Carrillo rod becomes more consistent and reliable from the first point of manufacturing all the way to the extreme uses in the racing world.

Shot peening relieves tensile stresses built up in the grinding process and replace them with beneficial compressive stresses and increase fatigue life. Shot peening is a cold working process in which the surface of a part is bombarded with small spherical media called shot. Each piece of shot striking the material, acts as a tiny peening hammer, imparting to the surface a small indentation or dimple. In order for the dimple to be created, the surface fibers of the material must be yielded in tension. Below the surface, the fibers try to restore the surface to its original shape, thereby producing below the dimple, a hemisphere of cold-worked material highly stressed in compression. Overlapping dimples develop an even layer of metal in residual compressive stress. It is well known that cracks will not initiate or propagate in a compressively stressed zone. Since nearly all fatigue and stress corrosion failures originate at the surface of a part, compressive stresses induced by shot peening provide considerable increases in part life.

All critical CNC machines at CP-Carrillo are equipped with probing to accurately validate dimensional integrity. In the production process each part is magnafluxed at least twice, further each piece is Rockwell tested to validate the heat treat procedure.  A final controlled and validated shot peen operation completes the part. Once manufacture is completed, the rod a job number is lasered for traceability.

CP-Carrillo offers two types of fasteners: H11 tools steel (WMC) and a Multiphase (CARR) Fastener. The difference is in the material and the longevity. The H11 tool steel bolts are good for about 15-18 torque cycles and the Multiphase fasteners are good for indefinite torquings when stretch method is followed for installation.

CP-Carrillo uses a proprietary steel to manufacture its connecting rods, named Carrilloy. It is a chrome, nickel, moly, vanadium alloy which meets all VAR (vacuum arc re-melt ASTM standards). Carrilloy is simply a modification of an existing SAE specification.  We just tighten up the acceptable attributes of the heat as it is manufactured. The heat is validated, both by the supplier and an independent metallurgist whom confirm the desired physical and chemical properties of steel.

Every rod leaves our facility with a specification card.  This spec card displays a part number, critical dimensions, weights, job number and bolt installation chart; all for ease of identification and tracking.

Since 1963, the name Carrillo is recognized as the preeminent custom connecting rod manufacturer in the world. CP-Carrillo has provided custom and prototype connecting rods to virtually every major automotive and motorcycle venue, most notably to the high performance and speed equipment industry. Whether it is a development engine or a modified existing engine, when nothing but the finest, most accurate, proven part is needed, Carrillo earned the reputation of simply being the best. In addition to our well known H beam connecting rod, we offer an A beam configurations as well. All versions of Pro-H and A are stocking parts, which are limited to the more popular dimensions and part numbers. To decide which beam type is best suited for your application, please call our Technical Sales staff. Together we can build a rod that is best suited for your application and needs.

The fastener system of a high performance connecting rod is most likely the most critical unit of the assembly. As a result it is important that the fastener is installed per instructions and with recommended lube. CP-Carrillo has close to fifty years of experience of working with what have become the most recognized fasteners in the connecting rod industry. Much of this has come from experience which has been tested and validated repeatedly.
Each CP-Carrillo fastener design is based on a known yield load. During linear stretch of the bolt this load should never be reached. The recommended stretch value is 80% of yield load calculated in a tension – torque diagram.
Torque figures are the more commonly used method for tightening fasteners, however this is not CP- Carrillo’s preferred method and we will explain why: Torque is affected by numerous variables, all of which can alter the true preload figure you are trying to attain. Particularly, the lube utilized, the condition of the threads, the spot face, dimensional integrity, as well as other variables have an effect. Nearly all of these elements are alleviated if the assembler uses a “stretch” method. CP-Carrillo found that the consistency of high quality fasteners offers the least deviation when using the stretch method, with the result that the fastener will exhibit proper preload using designated stretch.

CP-Carrillo is often asked about general horsepower ratings for the various designs of its connecting rods. Unfortunately, this cannot be answered in a simple way. The most relevant rod design parameters are Inertia forces (a function of engine speed, crank train geometry and assembly weights) and Cylinder firing pressure (tuning, fuel, boost, etc.) Through increased engine speed, displacement, firing pressure or a combination thereof, horsepower is gained. However, though the various changes in the cycle, the demand on the rods varies greatly. Moreover, extreme dynamic loads on the drive train such as intermittently free spinning wheels or propellers (Hill Climb races, Off-Shore boat races) should be considered the when making the right choice of rod. Based on our experience combined with our analysis methods we like to provide you with our best suggestion for your specific application.

At CP-Carrillo, we not only build high performance connecting rods, we provide service, knowledge and support.  Our high-tech design, engineering and manufacturing operation is backed by a world-class service department.  Our full staff of dedicated technicians, engineers and customer service is prepared to help with all of your design, application and service needs.

Throughout the manufacturing process and before leaving our facility, CP-Carrillo rods are under the control of a rigorous Quality Assurance system.  Each rod is subjected to a variety of inline quality checks, to ensure dimensions meet our stringent tolerance requirements.  We employ a variety of testing equipment to accurately assess these tolerances, including a CMM, Air and Height-Gages to name just a few. The initial quality assurance starts with our selection of material, followed by a strict forging and heat treating process.  As a rod moves through the manufacturing process, quality assurance follows every step of the process; testing dimensional integrity and quality, providing an electronic trail of certification throughout the entire manufacturing and shipping process. Thus enabling us to become ISO 9002-2008 certified.

Often copied, but never duplicated. We laser engrave Job number on the side of the cap, utilize CP- Carrillo fasteners and laser our logo on the beam. If in doubt, call our office and we would be happy to help identify your connecting rod.

Yes, we offer a hand held stretch gauge to check rod bolt stretch the proper way. Our gauge includes a special high-tension spring that allows adjustability for bolts up to 2.75 in. long.

Majority of our rods have great serviceability and we offer a recon service. Recon service includes a visual inspection and magnaflux. If the rod can be reconditioned, we check straightness and alignment, re-hone and re-bush. We check the bolts and perform a Rockwell test. Bolts are not included in the recon charge, but are available for purchase if a replacement is recommended.

We recommend using the lube we provide and here is why: Dimensional integrity is foremost importance-- the qualities of our fasteners have set the standard in the industry and we have continually looked at improved lubrication. The results of this continued effort is a new, improved lubrication for the fasteners. This is still molybdenum based lubrication grease, but with enhanced properties. CP- Carrillo lube offers an improved clamp load repeatability, greater resistance to high pressure and temperature (range -22F to 1200F), and no oil contamination. The coefficient of friction stays unchanged, even after several bolt re-tightening and loosening processes. The implementation of this new lube is simply another example of CP-Carrillo’s efforts to continue to offer the finest connecting rod in the industry.

Yes, you can buy a spare connecting rod. We try to match to +/-1 gram weight of the set. If it is a more popular item we should have a spare on the shelf, if not we will manufacture one.

Absolutely.  Our heat treat operations are designed by our contracted metallurgist.  We heat treat via the a mar-aged operation, resulting in UTS of 195,000 with a yield of 182,000 while maintaining the critical elements of low notch-sensitivity and ductility.