LO 8-3 Identify and describe the construction techniques and composition of cylinder blocks and outline the advantages and disadvantages of each design

LO 8-03: Identify and describe the construction techniques and composition of cylinder blocks and outline the advantages and disadvantages of each design.

Compacted Graphite Iron

Using CGI (or sintered graphite) for a block material is the latest engine block construction technique. The construction method and material provide blocks with greater strength, rigidity, and durability at a reduced weight and brittleness compared to cast iron. Theoretically, a CGI block can be constructed with the strength of steel but with almost the weight of aluminum. The stronger, steel-like-strength material enables the use of thinner block and cylinder walls without sacrificing stability or strength. CGI construction starts with powdered iron and graphite alloys squeezed into molds at high pressures that are then heated to bond the metal particles together. This construction technique yields blocks with at least 80% higher tensile strength, 45% greater stiffness, and approximately double the fatigue strength of conventional gray cast iron and aluminum. The weight of an engine block made from CGI alone can be reduced by 22% through a 15% reduction in the thickness of the block walls. Noise transmission through the block is dramatically reduced as well because of the vermicular (wormlike) grain structure of the material, which has sound-absorbing properties. By reducing the block size and weight while increasing strength, CGI materials allow engine designers to improve power density, performance, fuel economy, and durability while reducing engine weight and noise. Many LD, MD, and HD diesels are now made from CGI, including blocks from Audi, Cummins, International MaxxForce 7.0 L (427 in 3 ), 13.0 L (793 in³), and the latest Navi star A25 12.4 L (757 in³). Other models include John Deere 9.0 L (549 in³), Paccar MX-13 (in which both block and cylinder head are made from CGI), VM Motori (Fiat Chrysler Automobiles [FCA] RAM 3.0 L [183 in 3 ] EcoDiesel), and Ford’s F-150 3.0 L (183 in³ ; introduced in 2018) and 6.7 L (409 in³) Power Stroke (introduced in 2010). Ford claims that the 6.7 L (409 in³) Power Stroke is made from patented SinterCast CGI material that is 40% more rigid and 100% more fatigue resistant than gray cast iron Figure 23. CGI has allowed Ford designers to reduce the engine block wall thickness by 15% in comparison to the thickness that would be needed if it used gray cast iron. A weight reduction of 160 lb (70 kg) is achieved in comparison to the earlier cast iron 6.4 L (391 in³) engine.

CGI engine blocks have their own unique service challenges in terms of machining. CGI is steel-like in hardness but also abrasive and “gummy” to cutting tools when machined. Special machine tools with extraordinary hardness are needed to cut the material. Honing cylinders of CGI blocks is much more difficult due to the harder material; a coarse-grit honing stone will produce a smoother finish than the same stone will produce in a cast iron block. CGI blocks cannot be repaired when damaged, so they must be replaced.

FIGURE 08-23: A popular example of a CGI engine block is the Scorpion 6.7 L (409 in³) Power Stroke. CGI block material provides for a quieter, stronger, and lighter design.

©2026 - CDX