In setting out the engine specification, MCT had to take account of the fact that the Daytona 24-hour race covers 3,000 miles and that longevity was therefore essential. The other 2004 season races ranged from 200 miles to six hours, which would equate to over 600 miles. Qualifying engines are not allowed. An ideal engine platform for the new car was available in the form of the Infiniti Q45, an all-aluminium, DOHC, 4.5 litre V8, an engine which MCT used as the base for the forty engines they prepared and supplied to the single-make Menards Infiniti Pro Series (MIPS).

This series was set up as a feeder into the IRL championship and the Indy 500, using a spec chassis from Dallara and spec engine from MCT. The engine was developed to produce 450 bhp from 3.5 litres at a fixed cost, and the 2003 season saw 19 drivers use it in 12 races with no failures, thus providing a valuable durability history to MCT. With a change of capacity to 4.35 litres, the engine was brought up to a maximum capacity within the 2100 - 2125 lbs car mass bracket, the Grand-Am benchmark performance of 500 bhp and 400 lb/ft was predicted to be exceeded.

MCT used one-D analysis code validated against real MIPS test data to derive the initial specification for the new Grand-Am engine. Keeping the MIPS engine combustion chamber shape meant that combustion and dyno data could be carried over accurately to support the validation. Early predictions showed that in addition to the swept volume, several other changes would be required. Airflow through the inlet and exhaust ports would need to be increased by 7% and 12% respectively, and valve lift would need to be increased by 18% and 33% respectively. Further improvements in inlet airflow were realised by increasing the throttle area and by re-profiling the inlet valve.

The crankshaft design was changed to provide a bespoke design for the series, through extensive analysis utilising our in house resource, a mass reduction was also achieved despite the increase in throw. The consequent changes to valve lift and firing order meant that the Q45 cast-iron camshaft blanks could no longer be used, nitrided steel camshafts were therefore adopted for the new Grand Am design.

Piston speed was reviewed in the light of the required rebuild interval. Previous experience showed that 22.5 - 23.0 m/s would be acceptable and the projected stroke at 4.35 litres conveniently resulted in 22.7 m/s @ 8500 rpm. The 2000 Opel DTM engine, originally designed by MCT engineers, also had a requirement for a long-life (by racing standards) at 5000 km, so was deemed to be a good physical guide for the Grand-Am engine. FE analysis using Abaqus validated the piston design.

Early durability testing of the MIPS engine on rigs and dyno had thrown up unacceptably high wear rates of valves and guides. A development programme had resulted in replacement of the standard sintered steel guides with Colsibro, and identified that the surface finish on the PVD-coated valves was causing the wear. Although the production titanium valves were retained, their relatively low price was offset by having to super-finish the valves to give a stem Ra value of 0.15 - 0.20 µm. For the Grand Am engine the valves were replaced with steel items, the increased valve mass and higher acceleration from the new cam profile required MCT to design a new valve spring with a predicted float speed of 9,600 rpm. The bespoke wire valve spring design software of MEL also crucially predicts stress levels, even taking account of the relative movement of individual coils. Valve springs are often the Achilles heel of endurance racing engines, and wire springs are mandated by the Grand Am rules, so careful design backed up by rig testing was required.

MCT usage of rapid prototype technologies allowed the team to accelerate intake system testing and development programmes. For the initial manifolding, a sintered steel with an epoxy filler was chosen to make the dyno inlet manifold, this emerging material allows parts to be built up directly from CAD models using a laser to bind steel powder in 0.1 mm layers. Components are then baked in a furnace and are ready for use with minimal machining. Manifolds were made over a weekend and assembled and tested the following week.

The engine was fully approved in Dec 2005