At 170HP the 4.1L doesn't have much more juice than the L44 140HP MPFI 2.8L HO. The 4.1 was the GM test mule for free standing cylinder liners so they had issues with gaskets. I'd look for a 4.5L or a 4.9L. If you have your heart set on a 4.1 get the "improved" later production block. The later blocks had ribs in the casting. These are the ones you want. There's a thread on Pennocks Fiero Forum about this motor titled "Why does the 4.1L caddy suck."