Originally posted by grapeape
The I-Beam rod is the most popular type of connecting rod. It is what almost every engine manufacturer uses as original equipment. They are cheap to make and very reliable. They can be made as strong as is needed for the application and are well supported by the aftermarket. Even stock I-Beam rods can handle much more power than they were originally designed for with some careful prepping, as shown in the Prepping Stock Rods article. With the aftermarket support today, you may find that the time and money spent on prepping stock rods is not the best option. There are inexpensive rods for most popular engines that can handle more power than prepped stock rods (as well as save you a lot of time).
H-Beam Rods
H-beam rods are becoming more popular. They have some benefits over an I-Beam for certain applications. For high hp, low rpm engines, the rods need more strength in compression. For high rpm engines, rods need tensile strength. Today the use of nitrous, blowers and turbo's is getting very high hp at lower rpm levels, so tensile loading is not as much of a problem as it used to be. This is where an H-beam design can pay off. With high rpm, the tension on the rods are pretty much straight, so when the rod fails, it's usually torn apart. The teasel strength of a rod is most dependent on the material and the cross section of the rod, so for that application the shape (I-Beam or H-beam), has little bearing on strength. For compressive loads, this all changes. When I rod fails from compressive loads, it bends. The compressive loads are not straight, this makes the shape of the rod very important to strength. The design of an H-Beam rod helps them resist bending more than an I-Beam design. Well, let me clarify that a bit, an I-Beam rod can resist bending about the same as an H-Beam, but the H-Beam does it with less weight. Many people have argued that H-Beam rods are not any better and are a waste of money, and their number 1 argument is that you'll never see an H-Beam aluminum rod and all big racers use aluminum. To make sense of that, just think about what an aluminum rod is designed for. They are designed to reduce rotating and reciprocating weight, for high rpm engines. Aluminum is a poor choice for a high output low rpm street engine like a nitrous, blower or turbo motor. My twin turbo small block make peak power under 6000 rpm, ultra light reciprocating parts are not a big concern to me, strength is. I chose H-Beam rods to handle the very large compressive loads.
