The Ultimate: Bamford Rose 4.7L GT4

For builds starting with a 4.3L engine, the block is bored out with the bore increased from 89mm to 91mm (the new piston grade is selected to match bore dimensions). Note also that also an engine built from a 4.3L basis will additionally have its stroke increased from 86mm to 91mm.

The most important removal of metal, however, is the work undertaken on the cylinder heads. The cylinder head is CNC machined with combustion chamber reprofiling, volume optimisation and regrinding of valve seats. This reprofiling and volume optimisation enables the compression ratio to be raised from 11.3:1 to the optimal 12.5:1. This is a ratio which is unachievable in production engines because of the tooling safety margins required to account for wear. CNC machining is also used to port and re-profile the intake and exhaust ports to optimise (c+20%) gas flow throughout the engine. The original engine inlet valves are replaced and upgraded to 36.99mm valves manufactured to the highest standards. These valves are 1mm larger than the standard 4.7 inlet valves (2mm larger if a 4.3 engine is used as the basis of the build).

Additionally, the rotating and reciprocating systems of the engine are upgraded to forged connecting rods and forged pistons. The standard OEM crank is of very high quality so there is no need to upgrade it (an original 4.3 crank, will be replaced by a 4.7 item), however, crank web weight balancing was skimped at the factory so we dynamically balance.

The Bamford Rose build is, however, much more than just the best quality components and machining.

Each component is subject to pre-machining, lightening and balancing to F1 tolerances. Compare the OEM standards with our standards for the components below;

• Piston weight variance minimum to a maximum Aston OEM part tolerance = 7.6grams. Variance from Bamford Rose = 0.1gram
• Connecting rod variance minimum to a maximum Aston OEM part tolerance = 4.6grams. Variance from Bamford Rose = 0.1gram
• Crankshaft balance at flywheel end Aston OEM part =2,014 g/mm. Variance from Bamford Rose after dynamic balancing =32.3 g/mm
• Crankshaft balance at damper end Aston OEM part =2,118.5 g/mm. Variance from Bamford Rose after dynamic balancing =48,45 g/mm
• Lightweight flywheel balance = 54.44 g/mm Original car damper pulley balance = 199.2 g/mm Original car damper pulley balance after dynamic balance = 22.4 g/mm Lightweight damper pulley balance = 140.22 g/mm Lightweight damper pulley balance after dynamic balance = 8.0 g/mm

This attention to detail transforms the engine. The lightening and balancing work makes the engine feel super smooth and also dramatically improves throttle response. This smoothness additionally improves engine durability dramatically reducing vibrations that contribute to engine wear.