Its simple really, it was the better engine for the car and which is why its in the car. The camaro with LT1 has same underhood as the CT5, CT4 is way smaller and a small block just doesnt fit to OEM requirements. Open up the hood and also note how tucked that LF4 is and its behind the front axle. The LF4 is truly a marvel and one reason why I bought the car too, I personally love that engine and it makes more power than the LT1 and is lighter (and costs a lot more so it wasnt a cost play). I own a few small block cars and my CT4 doesnt make me ever wish it had one. I needed some turbos in my life