To outsiders looking in, hot rodding can seem rather juvenile. We are talking about grown men who still play with blocks, for goodness sakes. Rather than groveling in shame, however, it’s time to embrace our natural gravitation to these large lumps of iron (or aluminum) and learn all there is to know about them. Let’s face it: Stock cylinder cases are fine for many engine builds, but keep on pushing the limits of horsepower, and sooner or later you’re going to need an aftermarket block. Aside from the irrefutable advantages in strength that they offer, aftermarket blocks are packed with goodies that promote easy cubic inches and unparalleled reliability. Thicker cylinder walls, priority main oiling systems, four-bolt main caps, and commodious crankcases are common fare on any aftermarket block, and the ante can easily be upped with taller decks and raised cam tunnels. The one downside to all these options is that the selection process can get confusing. That’s why we called up Jack McInnis at Dart to sort through it all.
Dart is a company that needs no introduction. Founded by legendary Pro Stock engine builder Richard Maskin, the Dart brand has been synonymous with high-end engine components for decades. Although the company’s rugged aftermarket blocks have been staples of potent street and all-out race cars for decades, it has recently ramped its block program way up. Not that long ago, the Dart block line was comprised of the Little M and Big M blocks. However, in just a few short years Dart has diversified its portfolio substantially. These days, there are multiple variants of Big M and Little M in addition to tall- and short-deck blocks, siamesed blocks, full-water blocks, aluminum blocks, spread-bore blocks, race series blocks, and even a Vortec 8100 series block. That’s a whole lot of blocks. In addition to explaining the differences between them, we used this opportunity to explore the different types of alloys used during the casting process, and also picked up some useful tips on how to keep extreme cylinder pressure sealed in the bores.
Aftermarket Block Basics
When GM was manufacturing small- and big-block Chevy engines, the typical production rate for an assembly plant was one car coming off the assembly line every minute. This meant that every part of the car, including the engine block, was designed with reducing manufacturing time and cost as top priority. In contrast, Dart blocks are designed and manufactured with performance as the number-one priority. The alloys, casting designs, and machining methods are all geared toward performance. Our blocks are heavier than stock because more metal is added to strengthen critical areas, and provisions for upgrades are integrated into the block as well. For instance, all Dart blocks have a true priority main oiling system that supplies oil to the main bearings first, then feeds the cam and lifters. This is the opposite of a standard OE small-block oiling system. The standard system was designed to simplify high-speed production and works adequately for normal passenger car use, but for high performance using a priority main system is vastly superior. Additionally, Dart’s four-bolt main caps feature splayed outer bolts, which go into the strongest part of the bottom end. The stock four-bolt design used straight bolts that actually weaken the main webs, which is why many engine builders prefer two-bolt blocks over the OE four-bolt design. All our blocks also have expanded water jackets for better cooling, and blind head boltholes, which don’t go through into the water jackets, eliminating leaks from the head bolts.