BoostLine Connecting Rod Design

Not all rods are created equal. Take a deep dive into what sets BoostLine connecting apart as we explore the processes of design, engineering, and manufacturing a boost-ready rod.

When it comes to the rotating assembly, connecting rods can be a bit of an afterthought for builders, with piston design and crank selection often positioned near the forefront of the build strategy. But not all rods are created equal, as BoostLine’s products clearly illustrate. Engineers took a clean sheet approach with these designs, taking the best attributes of many connecting rod styles and merging them into one purpose-built connecting rod that’s capable of handling over 2000 horsepower right out of the box.

BoostLine connecting rod patented 3-pocket designBoostLine connecting rod patented 3-pocket design
BoostLine's patented 3-pocket design is purpose-built for the rigors of boost.

“The primary application for these are forced induction or nitrous combinations,” explains Nickolaus DiBlasi, Director of Product Management for BoostLine Products. “There may be some folks who would use these in a naturally aspirated build, but it’s really intended for folks who are making big power. But no matter what kind of build you’re doing, this is likely to be the last solution you’re ever going to need.”

FEA showing improvement in bending strength for BoostLine rodsFEA showing improvement in bending strength for BoostLine rods
Because of the high cylinder pressures associated with big boost, BoostLine engineers focused on making the rod more resistant to bending under massive power loads.

While aluminum rods offer some inherent benefits, DiBlasi notes that their longevity is a relative unknown. “The thing about aluminum rods is that you have an unpredictable failure rate – nobody really has good data on how long an aluminum rod will last. The difference between steel and aluminum in that regard is that you’re going to get much, much better life out of a steel rod. These rods are for the guy who’s running a 1,500 hp LS on the street, or a someone with a thousand horsepower Supra that sees double duty as a competition car and a daily.”

But there’s much more to BoostLine’s connecting rods than simply the 4340 forged steel used to produce them. To get a better sense of what makes these rods stand out from the pack, we dove into BoostLine’s development and manufacturing processes with DiBlasi and one of BoostLine's lead engineers, Thomas Van.

BoostLine connecting rod in-process inspectionBoostLine connecting rod in-process inspection
BoostLine rods are carefully finish machined in-house and inspected to within .0001in on aerospace-grade inspection equipment.

Heavy-Duty Goes High Tech

Although BoostLine’s three-pocket design is geared toward massive power, the team’s ability to leverage sophisticated development technologies resulted in a rod that wasn’t excessively heavy in order to provide that level of durability. “The clean sheet approach gave us the opportunity step back and look the design on a fundamental level,” says Van. “And because we have this huge repository of data to work with from our other products, we know what people are doing with the pistons, the rings, the cranks, the blocks, etc. We have a better understanding of the entire picture what these rods are going to need to handle because we touch every part of the engine.”

Armed with that data, BoostLine developed a product that was distinctive even on a visual level. “When we progressed through development and started doing finite element analysis, this ended up being a good, strong design that also kept the weight to a minimum,” Van says.

In the quest to maximize the performance and durability of these rods, BoostLine put every aspect of the design under the digital microscope. “For each application we were 3D scanning blocks and OEM connecting rods to determine what we felt the maximum envelope was,” says Van. “We’re limited by block geometry, so working with our development partners, we were able to determine how we could provide as much strength as possible in a very specialized manner for each application while working within the given envelope.

It also helps that we know what people are doing with these engines – for instance, we might note that there aren’t really any stroker cranks available for a given application, so we’d optimize that specific part for a stock stroke. But in other cases stroker cranks are very common, and we obviously want to support that, so with each application we really try to look at the whole package and anticipate how these rods will be used.”

BoostLine connecting rods available for domestic and importBoostLine connecting rods available for domestic and import
BoostLine rods are available for a plethora of domestic, diesel, import and European engine applications.

The finite element analysis process that Van mentioned earlier also plays a significant role in the development process. “FEA is something that engineers can use to determine stress levels in a part,” he says. “Putting a component through that process gives us better understanding of how and why a part might fail. In the past people would just do simple calculations to find a general range, or they’d produce the part the way they felt it should be made and then just do trial and error testing. We now have the option to come up with new ideas and try them in the software before moving to the prototyping phase. We can try ten, twenty, even fifty different designs if we want to, and while it’s still a labor-intensive process, it allows us to develop parts more precisely and efficiently. 

That, in turn, yields a better part. “With some of our competitors, you’ll notice that their rods are really heavy,” says DiBlasi. “And that’s because they have to build an extra factor of safety into the design because they’re not doing this kind of advanced, data-driven analysis.”

BoostLine connecting rods ARP boltsBoostLine connecting rods ARP bolts
All BoostLine rods come standard with ARP 2000 series bolts but can be upgraded (in sport compact applications) to ARP 625+ bolts for even more strength in extreme power applications.

State Of The Art Production

BoostLine forges their rods from 4340 steel, after which they are then milled and machined. “We fully machine the part not only to get the geometry we need, but also to keep our tolerances tight,” DiBlasi points out.

“We probably have the most comprehensive inspection process in the industry, and that’s to make sure that the product is perfect for the customer. Everything is measured to .0001 of an inch on a coordinate measuring machine. This is something you’d normally find in aerospace factories. All of BoostLine’s rods are put through two comprehensive inspection processes, and we provide an itemized sheet that is custom tailored to every set of rods we send out which gives you the exact dimensions, the weight spread – basically everything a balancer is going to need to use our rods in a setup.”

BoostLine rods 1,000 horsepower K series Honda build - 4 PistonBoostLine rods 1,000 horsepower K series Honda build - 4 Piston
Top builders such as 4 Piston Racing trust BoostLine connecting rods in their high-power turbo builds. Shown is a set of BoostLine Honda K series rod.

And every set is also weight-matched to two grams. “Matching rods to within two grams of one another isn’t an easy task over that large of a distance, especially when you’re using steel,” he adds. “But it’s also pretty critical in our opinion. It’s just one of those things that we’re doing above and beyond the standard to ensure that exactly what you’ve asked for is exactly what you’re getting.” 

BoostLine connecting rod CMM inspectionBoostLine connecting rod CMM inspection
Weight-matching to two grams isn't the only critical component of connecting rod quality. Each BoostLine rod is also subject to a 25-point inspection on CMM equipement to ensure manufacturing accuracy.
BoostLine connecting rod inspection reportBoostLine connecting rod inspection report
Each set of BoostLine connecting rods is supplied with an inspection report detailing all critical specifications obtained the 25-point inspection, eliminating any guess work.

A Rapidly Growing Lineup

BoostLine now offers connecting rods for a wide range of different engine applications, including GM’s LS family of engines, Chevy big-blocks and small-blocks in various lengths, Ford’s modular V8s, Gen III HEMI, GM and Cummins diesel, Mitsubishi, Honda, Subaru and more applications. BoostLine is always in the midst of identifying the next round of engine applications that can benefit from BoostLine rod technology.

All BoostLine connecting rods include ARP 2000 bolts as standard, which are rated to a clamp load of 220,000 PSI. ARP Custom Age 625+ bolts are also available for certain applications, an upgrade that extends that rating to 280,000 PSI. BoostLine diesel connecting rods utilize ARP 2000 12mm fasteners, both improving clamping force and aiding in ease of engine assembly.