Today's aftermarket engine part manufacturers are making everything under the sun from stock replacement parts to wow, that's possible to build? In a nutshell it seems like we have the parts covered for just about every application of the small-block Chevy we want to build. So where to begin, or better question is, what is the weak link to your current engine? Usually we find out when it's to late, like in my case of a broken crank. This was all my fault because I was pushing the limits of what the last crank could do. Some of you may say it was a bad crank and I have to disagree – it was my driving habits.
In my case, repetitive 6,000-plus-rpm shifts with almost 456 hp and 481 lb-ft was pushing the capacities of the cast crank material. The good news is that the engine never self-destructed, but it did send main bearing material all through the engine. One of the positive things in all of this is that we can now provide you guys, the readers, with some details on how to beef up the bottom end and squeeze some more power out of that old small-block.
Although a plethora of available engine parts may be a logistical nightmare for novice engine builders, companies like Lunati, Comp Cams, Summit Racing, and Airflow Research (AFR) all have tech lines to help you. Mix and match the wrong parts and you'll wind up not making any more power than you started with, so start by doing some research. Questions I would ask include, do you want a stump-puller engine that will not rev up past 5,500 rpm or do you want an engine that revs to the moon, but has trouble getting the truck moving? Or is it a combo of the two? For me I definitely want the engine to rev, but I also want the engine to pull like a freight train from off idle to max rpm. The best way to achieve this is by choosing parts that work well together. Let's talk about the 383 bottom end and different rod lengths, etc.
Popular 383 kits have a 3.750 stroke crank, 5.70 rods, and 1.425 pistons, and if you add up the total of the combo you get a 9-inch deck height. This kit is popular because pistons are available in different CC's from dished, flat-top, and domed. The Lunati VooDoo Engine Kit we choose has a non-twist forged 4340 steel crank with a 3.750 stroke (part number 70137501), 6-inch H-beam rods (part number 70160001-8), and a shorter piston compression height of 1.130 inches (part number 201006K1) kit with rings and pin.
The Lunati Balanced Kit comes with main bearings and rod bearings that are designed to fit the standard small-block. So why did we choose to go with the longer 6.0 rods versus 5.7 rods? The 5.7 rods with the 3.750 stroke have what is called sidewall load. When the 5.7 rod and piston is at top dead center (TDC) or bottom dead center (BDC) the piston is forced to the side of the block causing increased friction. The 6-inch rod will have the wrist pin sit higher in the piston which optimizes the rod ratio for higher rpm's and puts less stress on the cylinder wall because of the decreased angle the rod is at during its cycle. The downside to the long-rod build is that the piston has smaller ring-lands due to the higher wrist pin location, so it is not as conducive to a boosted application.