Aluminum Blocks
Jack McInnis: "The perception that aluminum blocks lose power through decreased ring seal, as compared to iron blocks, is largely based on early aluminum blocks, which lacked the integrity we can achieve today. Aluminum blocks might have sacrificed power many years ago, but that's not the case anymore. A properly engineered modern aluminum block will make the same power as an iron block. We were recently involved in a direct comparison test with a big-block dragster engine making in excess of 1,100 hp. The engine was assembled and dyno tested with an iron Dart block, then disassembled and rebuilt using an aluminum Dart block. At the end of the day, the power figures were nominally identical for the iron and aluminum blocks."

Jason Neugent: "In the early days of manufacturing aftermarket aluminum blocks, the material that was used did indeed move around a lot under heavy abuse. This caused the cylinder sleeves to move, sink, or go out of round. The consequence was that this deflection would cause water leaks and poor ring seal, which are prime ingredients for poor reliability and power loss. Today we have solved these problems with the use of our virgin A-356 aluminum recipe, tighter tolerances, and more rugged sleeve materials. In independent testing, Brodix has witnessed our own aluminum blocks seal as well as a quality cast iron block."

Core Shift
Jack McInnis: "Core shift can be a major issue on some production blocks, as it results in inconsistent cylinder wall thickness from one block to another. Dart addresses the core shift issue in a couple of significant ways. We design and machine our own tooling for greater control of the mold-making process. Most importantly, we qualify and machine every block to maximize the cylinder wall thickness in the finished piece. Dart's CNC machining centers are designed to hold extremely tight tolerances over long production runs. Likewise, our fixturing process cuts down on the number of setups required and reduces stack-up tolerances. We also inspect our cutting tools at specific intervals to ensure that surface finishes are optimal in the machined parts, and continually check the finished blocks for quality control. In comparison, an OE block would be located for machining based on an external surface to speed production, which makes cylinder wall thickness very inconsistent. Dart blocks are actually located to maximize cylinder wall consistency during machining. Our block castings are made with much more attention to detail than the mass produced OE blocks, and this hands-on approach keeps core shift to a minimum."

Jason Neugent: "At Brodix, we have the advantage of having our own in-house foundry. As a result, our core shop is right next door, making it easier to monitor the entire casting process. With this arrangement, making changes to the tooling or machining is much easier and more efficient. Consequently, our aftermarket blocks are made with much tighter tolerances and much better core prints. Our system for coring blocks is very modern and watched over daily. Unlike the OEMs, we're not making thousands of blocks per week, so this lower production volume allows us to maintain better quality control. If there is a problem, we can catch it early on and scrap the problem blocks. On the other hand, if you're paying an outside foundry and don't catch a problem until several hundred blocks have been cast, you might be more inclined to try to fix the blocks and put them into circulation."

Rocko Parker: "Core shift is unacceptable in a performance engine build, so the new GMPP LSX block has five additional core plugs. This allows for the sand casting cores to make contact between the outside of the block and the cylinder liners. In total there are six supports inside and outside of the block when the iron is poured into the sand mold at the foundry. These additional efforts help keep the core from shifting."