Nissan RB26DETT N1 engine block (casting code 24U) is the reinforced high-performance version of the legendary Skyline GT-R inline-six. Designed by NISMO for Group A and N1 endurance racing, it features thicker cylinder walls, revised water passages for better cooling, and a higher nickel content in the iron for superior structural rigidity.

Listing Details

• 2.6-Liter RB26DETT Inline-Six Engine Block
• Manufactured by Nissan
• Produced for N1 Skyline GT-R Models
• Cast Iron Construction
• Main Bearing Caps & Studs
• Manufacturer’s Packaging

In 2026, the N1 block remains the gold standard for builds exceeding 700–800 hp, where the standard 05U block is prone to “crack-walking” or cylinder wall failure under high boost.

1. Key Technical Differences

While the N1 block looks nearly identical to the standard block externally, the internal reinforcements are what command the premium price.

2. 2026 Market Value & Availability

The N1 block has officially entered the “collector asset” phase. Following the NISMO Heritage Parts program relaunch, new units are produced in limited batches, but demand consistently outstrips supply.

• Bare N1 Block (New/NOS): $7,500 – $9,500$

  • Note: Some specialized retailers (e.g., GTR Europe) have listed new units as high as $70,000+ when sold as a complete, verified assembly.

• Used/Core N1 Block: $4,500 – $6,500$

  • Caution: Always borescope used N1 blocks for “core shift” or prior over-boring. If a 24U block has already been bored to 88mm, its structural advantage over a fresh 05U block is largely diminished.

• Billet Alternatives: $12,000 – $16,000$

  • For extreme builds (1,500+ hp), many builders are now pivoting to Billet Aluminum blocks (like Bullet or Mazworx), which are lighter and even stronger than the iron N1.

3. Verification: How to Spot a Fake

Because of the massive price gap between 05U and 24U, “fake” N1 blocks (restamped 05U blocks) are a known issue.

• Casting ID: Look for the 24U stamp on the rear-left side of the block, near the oil filter housing. The font should be crisp and consistent with factory casting.

• The “V” Groove: Genuine N1 blocks often have a specific “V” shaped casting mark near the bell housing area that is absent on standard blocks.

• Weight: An N1 block is slightly heavier (approx. 1–2 kg more) than a standard block due to the extra material in the deck and walls.

4. Buying Recommendations

• For Street Builds (<600 hp): Save your money. A brand-new NISMO Heritage 05U block ($4,200 – $5,500) is more than sufficient and much easier to source.

• For Competitive Racing: Insist on a New N1 block or move directly to a Billet block. The risk of fatigue in a 30-year-old used N1 core often outweighs the savings.