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Fasteners

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 pays close attention to the above mentioned variables. Dimensional integrity is foremost -- the qualities of the 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. This product 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.

PRODUCT UPDATE – Pro Series 3/8 CARR FASTENERS (PN# BLT-CARR6-PS)

As load requirements have increased over the years, CP-Carrillo developed an improved 3/8 CARR fastener to meet the rigorous performance standards one expects from Carrillo connecting rods. This fastener, known as the 3/8 CARR Pro-Series, has been used in many forms of racing.  This stronger, higher clamp load 3/8 PS CARR fastener is replacing our standard 3/8 CARR to provide the best performance fastener in every application.   The 3/8 PS CARR bolt has a thicker shank and does requires more bolt stretch, to get the desired clamp load. Please follow the instructions closely.

The Standard 3/8 CARR fastener (PN# BLT-CARR6) has the head marking of S6-X-XXX

The Pro-Series 3/8 CARR fastener (PN# BLT-CARR6-PS) has the head marking S6-X-XXX-PS

 

Installation Instructions:

  • Con rod supplied with 3/8 PS CARR fastener:

Use the listed stretch number of 0.0065-0.0075” to get the best performance of the PS Bolts.

  • Replace existing 3/8 CARR fastener without resizing the big end:

Stretch the BLT-CARR6-PS bolts to 0.0060-0.0065”, it is safe to go slightly higher as much as 0.0070” but bore may change slightly. Values must not be lower than 0.0060”.

  • Replacing 3/8 CARR fastener and resizing the big end:

Use the listed stretch number of 0.0065-0.0075” to get the best performance of the PS Bolts.

 

 

“Rather than simply offer instruction details we feel that if engine assemblers fully understand the dynamics of the fastener, successful implementation is achieved”.