Engine Tear-Down and Reasons for the Rebuild
The engine had been previously built elsewhere and had accumulated around 60,000 kilometers. At the turn of the year 2024–2025, we decided to inspect its condition. During the inspection, we discovered cracks in the pistons and that several pistons were missing pieces. We also made other observations that confirmed our suspicion that the engine needed to be disassembled.
In addition, the piston-to-wall clearance was too tight for forged pistons, which typically require a larger gap. It’s also likely that the engine had not been properly warmed up before driving, increasing the risk of damage when running forged pistons.
New Components and Tolerances
The engine block was thoroughly cleaned, and the cylinders were lightly honed and measured before ordering a set of CP forged pistons and Carrillo connecting rods. All clearances were measured and adjusted to suit the intended use.
The block was also inspected with attention to the fact that the new ARP bolt kit requires higher torque values, which can potentially distort the main bearing housings — a common issue that often leads to premature failure in built GT-R engines.
On a deeper technical level, bearing clearance accuracy and proper oil viscosity selection were emphasized. The oil was changed to one with the correct viscosity for these specific bearing clearances, replacing the previously incorrect 10W60 oil.
Balancing and Valve Clearances
The engine balancing was performed with greater precision than before: pistons, connecting rods, and their assemblies were balanced to within half a gram of each other. This significantly reduced the vibrations that had previously been noticed in the engine.
The valve clearances were adjusted by replacing the lifters — in this particular engine, the adjustment requires changing the entire lifter, unlike in some other engines (such as certain BMW engines) where the clearance can be adjusted directly.
Cylinder Head, Gaskets, and Camshafts
The head gaskets were replaced with original metal versions, and both the cylinder head and engine block surfaces were lightly resurfaced. This process introduced a challenge with the fitment of the timing components, but it was resolved by modifying the alignment dowels.
Since the cam gears do not have built-in adjustment in the stock setup, the cam timing cannot be easily altered, which can slightly affect the camshaft timing after resurfacing the head and block.
Other Upgrades
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Charge pipes were replaced with flow-optimized components
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Radium crankcase ventilation system installed
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Turbos serviced
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Bell housing bearings replaced
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Front differential serviced (bearings and seals replaced)
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Injectors inspected and tested
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Wiring harness renewed and tidied up
Engine Specifications
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CP forged pistons
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Carrillo connecting rods and bolts (torqued by stretch, not by torque spec)
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OEM metal head gaskets
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Stock camshafts and stock turbos
Power Figures and Reliability
Last summer, the car produced 720 hp and 940 Nm of torque. A stock engine would not withstand this level of power reliably, which made the forged engine build essential.
The story continues — this GT-R is now being prepared for the 1500 hp+ range.