We must admit that the reason is quite logical.
The Cadillac CT5V Blackwing has been released. While it does not have the legendary Blackwing engine of the CT6V, it is still the most powerful and track-capable Cadillac ever built.
Despite these numbers, the LT4 may not be the most powerful V8 GM has ever produced. The LT5 can produce 755 hp (563 kW), and 715 lbft (969 Nm), in the C7 Chevrolet Corvette ZR1. In an interview with Cadillac Society, Mirza Grebovic, V-Series Blackwing Chief Engineering provided answers to your questions about why Caddy didn’t use the more powerful mill for their halo car.
Grebovic claims that they had considered using the LT5 to power the CT5V Blackwing, but ran into problems. The CT5-V Blackwing would be affected if the LT5 was incorporated into it.
Moreover, the LT5 engine requires dry-sump lubrication. This could lead to the engine not sitting as low as it does now, as the architecture of the Corvette is different from the CT5.
The CT5-V Blackwing doesn’t have the power to handle the LT5 and more power won’t necessarily make it faster, given the modifications required to the chassis to accommodate the V8.
Grebovic stated that although it would have been powerful, the car would not be faster on the quarter-mile track. “305 tires with that much power would prove very difficult to manage.” Grebovic said Cadillac Society.
If you are curious about the sound of the LT4 V8 engine in the CT5-V Blackwing, here’s a link: