An engine is no better or stronger than its rotating assembly: the crankshaft, connecting rods, and pistons, all paramount to longevity and power potential. A key part of a healthy rotating assembly is having the correct connecting rods moving the pistons up and down as the crankshaft spins. Callies makes a variety of connecting rods for different applications and they share some of the knowledge they’ve acquired on how to ensure you have the correct rods in your engine.
Choosing a good connecting rod for your engine goes beyond just a few size measurements; there’s a vast array of things to consider. Caley Lambert from Callies provides information on the three biggest things to look at when sizing your rods.
“First, what are your long term goal with the engine setup? Sometimes people will initially build an engine, with “future plans” and certain components such as the rods will need to be taken into consideration. Second, what is the application? A rod that would be great for a street/strip car may not be a good application for an all-out racecar. Third, what is the combination of the engine? Sometimes, certain strokes of crankshafts and rod lengths will cause interference in the block, requiring ‘clearancing’ of the block and/or rods. This clearancing can be avoided by using a smaller journal diameter rod, shorter length rod, or using a rod with an offset cap,” Lambert explains.
When you’re looking at building an engine, the type of connecting rods you select will be based on the specific type of build or power-adder,” Lambert continues. “Naturally-aspirated, turbo, blower, and nitrous builds will all require different connecting rods to see the best performance and fewest issues. “In a high-revving N/A build, guys will lean towards a lighter-weight and smaller big end journal connecting rod to try to shed as much mass as possible. In a big boost or nitrous application, weight should not be the major concern; the main point should be longevity and durability. These types of builds will typically have a heavier rod used in them.”
After you know what your plan of attack is with the engine build, then it’s time to get all of the crucial measurements required for the connecting rods. Lambert provides the variables you need to take into account when measuring for the connecting rods in your motor. “You need to measure for the big end and small end bore diameter sizes, widths, proper bearing clearances, as well as side clearance. You also need to get the correct overall length for the crankshaft stroke and piston compression height before you pick the connecting rods,” Lambert says.
Lambert’s final bit of advice when it comes to selecting connecting rods revolves around what not to do, and how to avoid mistakes people commonly make. “When it comes time to pick out parts, people will purchase a rod that’s good for a certain application, and try to reuse it for a different purpose. You can’t use a rod from an N/A build on a blower build — it will cause problems. Also, some people are driven purely by cost instead of what’s best for their application, and that can lead to serious failure of the connecting rod.”
Make sure you check out the Callies website for more information on how to choose your connecting rods and see all of the many connecting rods they offer!