As soon as GM's factory LS3 block hit the street, its large siamesed bore brought the potential for affordable, big-cube LS motors to the masses. Simply honing these blocks out to 4.070 inches and combining them with a 4.000-inch stroke nets an easy 416 cubic inches, which explains why that particular bore and stroke combination has become so popular with LS enthusiasts. BluePrint takes the displacement tally a few notches further by packing a 4.125-inch stroke crankshaft in its LS crate engines for a total of 427 cubic inches. While some engine builders contend that the stock cylinder sleeves are not long enough to support a 4.125-inch stroke, which can lead to piston rock and increased oil consumption at BDC, BluePrint worked with Mahle to figure out an effective solution. "Our chief engine designer was able to work with the engineers at Mahle to design a revised piston skirt to stabilize the piston at BDC," Dru Freese explains. "This eliminates concerns of piston rock and oil consumption. We can't be piston experts like a large OE piston supplier like Mahle, but we can work with them to leverage their technology to come up with something that solves the problem."
Camshaft duration plays a significant role in an engine's idle quality and drivability. Although BluePrint's primary focus is in the street engine market, customers still expect a healthy dose of power to go along with a smooth idle and a streetable torque curve, and striking a balance between both extremes requires extensive development work. Likewise, by maximizing cylinder head airflow, BluePrint is able to employ cam designs with shorter duration specifications and wider lobe separation angles to preserve drivability while still producing impressive hp figures. "The first thing we have to take into consideration is the application in which we are designing a new engine for. Once the application is finalized, we start the design process using computer simulation software, which gives us a good idea on determining camshaft specifications," Chris Larson explains. "This is definitely one of those areas where we do a lot of consulting and a lot of testing. Even though we have been designing crate engines for a very long time, it's still a good idea to consult with the camshaft manufacturers. After determining the basic architecture of the engine by analyzing specifications such as bore and stroke dimensions as well as cylinder head airflow, we then work with camshaft manufacturers to come up with three or four baseline camshafts we feel will work best in a given application. While dyno testing, we advance and retard the cam four degrees from the intake centerline until finding the installed position that delivers the best performance. This is a very time-consuming process, but it ensures that we not only choose the best cam design but also the best installed position. Idle quality and manifold vacuum play a very important role in the decision also. Since our engines are designed for street use, not racing, we need to make sure all these factors best fit our customers' needs."
Using a combination of SuperFlow and DTS engine dynos, BluePrint dyno tests every single engine that it builds to verify horsepower and torque output. Although hot rodders will naturally fixate on these figures, the dyno serves as the ultimate tool for ensuring quality control by simulating the operating conditions of a running engine as installed in a car. "We want to make sure that we can show our customers the power that their engine actually made. They are paying for that power and we want them to have the peace of mind that their engine is going to do what we say it will do," Chris Larson explains. "However, a lot more goes into a dyno session than extracting hp and torque numbers. Once we get the water and oil up to proper operating temperature, we set the idle rpm, ignition timing, and air/fuel ratio at idle and wide-open-throttle. To make sure that the engine is breaking in properly, we check the lifters to confirm that they are rotating and seating properly. Additionally, we check intake manifold vacuum, and run a dye through the oil system to check for leaks using a blacklight. By actually running every engine before it leaves our facility, it ensures that customers are getting the performance and reliability they expect from one of our engine packages. It really is the last quality checkpoint for an engine has before it ships out."
Pro Series engines
For those seeking maximum hp and durability, BluePrint recently introduced its top-of-the-line Pro Series engines. These offerings range from 427ci Gen I small-blocks with a stout 540 hp, to 632ci big-block monsters belting out 815 hp. Not surprisingly, Pro Series engines come packed with premium components. "Our original catalog of crate engines are based on seasoned blocks that have been bored, honed, decked, and align honed. These engines are very affordable and represent a great value," says Dru Freese. "However, we still had a lot of folks who wanted a new aftermarket block, which prompted us to develop our own unique block casting. Our BluePrint blocks boast thicker cylinder walls, taller deck heights, and additional clearance for stroker crankshafts. This allows building small-blocks as large as 454 cubic inches, and big-blocks as large as 632 cubic inches. Pro Series engines also feature hydraulic-roller valvetrains and forged rotating assemblies for the ultimate in durability."