Heads, GM Caprice LS1 engine heads. It has air intake porting. Sport springs, valves, and valve seals are all new. Of course, it's the best breathing head that fits a 5.7, 5.3 engine. With porting, it also gives great performance! The head is clean, no overheating. I was going to install it on a project I had, but it was canceled. Even if you want to install a big cam, you don't need to buy sport springs.