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Cadillac 42TT LTA specs: 255 ci (4.2L) 8-cylinder, 3.386 x 3.563 in (86 x 90.5 mm) bore and stroke, 9.8:1 compression. Rated 550 hp. DOHC.
The Cadillac 42TT LTA is close to square: 3.3858" bore against 3.563" stroke, within 5.0%, which splits the difference between a high-revving layout and a torque layout. The 3.563" stroke puts mean piston speed at 4,000 ft/min around 6,750 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 31.9 ci (522 cc).
9.8:1 on aluminum heads is in the range that usually runs on pump premium; aluminum sheds heat faster than iron, which makes the same number a little more forgiving.
It is one of 4 engines in the Blackwing family, sitting between the 217 ci and 256 ci members. Factory fitments include the Cadillac CT6-V, Cadillac CT6 Platinum.
| Displacement | 255 ci / 4.2 L |
|---|---|
| Bore | 3.3858" |
| Stroke | 3.563" |
| Cylinders | 8 |
| Compression ratio | 9.8:1 |
| Bore/stroke ratio | 0.95 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 550 hp |
| Bore/stroke character | 0.950 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,563 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 31.9 ci |
| Static compression | 9.8:1 — in the range that usually runs on pump premium |
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