CP Carrillo Connecting Rods Guide: WMC vs. CARR Fasteners Explained

CP Carrillo Connecting Rods Guide: WMC vs. CARR Fasteners Explained

Pushing a stock bottom end past its mechanical limits usually ends in catastrophic failure, specifically, a factory connecting rod exiting the side of your engine block. When you are investing thousands into big turbos, aggressive cams, and high-octane fueling, your rotating assembly needs to be bulletproof.

Based in California, CP Carrillo represents the undisputed gold standard in forged engine internals. Trusted in Formula One, MotoGP, and 3,000bhp drag racing applications, they combine proprietary metallurgy with relentless quality control. If you are forging your engine, here is why Carrillo connecting rods are the ultimate insurance policy for your block.

Seeking a set of connecting rods for your engine build? Check out our CP Carrillo brand page here!

The Carrillo Advantage: Precision & "Carrilloloy"

What separates Carrillo from budget forged rods is their manufacturing precision. Every Carrillo rod is forged from a proprietary chrome-moly steel alloy dubbed "Carrilloloy."

Unlike mass-produced rods that leave heavy machining work for your local engine builder, CP Carrillo rods arrive ready for extreme duty. Every single piece is:

  • 100% CNC Machined: Ensuring flawless dimensional accuracy and perfect grain flow.
  • Magnaflux Inspected: Subjected to magnetic particle inspection to detect any microscopic surface or sub-surface flaws before leaving the factory.
  • Weight Matched: Sold strictly in perfectly matched engine sets, balanced to an incredibly tight tolerance of +/- 1 gram.

The Rod Bolt Dilemma: WMC vs. CARR Fasteners

A connecting rod is only as strong as the bolts clamping it to the crankshaft. At 8,000+ RPM, the inertial load on the exhaust stroke actively tries to rip the rod cap off the rod. CP Carrillo offers two distinct fastener options depending on the severity of your build: WMC and CARR.

Fastener Spec Material Type Tensile Strength Best For Application Reality
WMC Bolts High-Grade Tool Steel (H-11 equivalent) ~220,000 psi Fast road, track days, and standard big-turbo builds. The benchmark. A robust, highly cost-effective fastener that provides serious clamping force. More than capable for 90% of high-performance street engines.
CARR Bolts Multiphase Super-Alloy (Custom Age 625+) ~285,000+ psi Endurance racing, extreme RPM, and high-boost drag builds. The ultimate upgrade. Delivers maximum clamping force to prevent big-end bore distortion under punishing cyclical loads, massive boost spikes, and extreme rev limits.


Which should you choose? If you are building a fast road car or a weekend track toy (e.g., a 500bhp EA888 or 700bhp B58), the WMC bolts will comfortably handle the abuse. However, if you are building a competitive motorsport engine, chasing 9,000 RPM, or pushing massive boost pressures that generate violent torque spikes, spending the extra money on CARR bolts provides unparalleled peace of mind.

No matter which fastener you select, ensure your engine builder strictly follows CP Carrillo’s exact bolt-stretch torque sequence during assembly to guarantee perfect clamping force.