My DD is a nearly perfect 85 Cadillac Sedan DeVille with the original HT4100 engine. It's one of the two engines they used when they were trying to get high fuel economy before the science was well understood and take my word it for they are not very good engines. In fact they are often ranked as one of the worst engines in history, and there is even a book out there blaming Cadillac's demise on that engine. I wouldn't go that far, but they are not very good.
Just for starters the flat tappet cams are very soft and are notorious for wearing out very fast (they go flat and you have no power after ~60k miles). Oh and the blocks are aluminum but the heads are cast, so they have different heat-up properties which produced a massive number of head gasket failures in the high-load rear-wheel-drive caddies (they do better with the FWD models). There are many engineering defects as well.
The 4.5 that came immediately after the 4.1 is better but still not very good. The 4.9 that came after that was a very good motor that corrects almost all of the problems found in the earlier series (roller cams, better components, etc). The 4.9 is basically a 4.1 that has been ported and stroked with an MPFI injection manifold (instead of TBI) with better parts, so if you can fit the 4.1 you can fit a 4.9. I have no idea why you would want to do such a thing.
After that came the Northstar engines, and the first couple generations of that had some pretty bad problems too, but the later ones are really good.
ps--my ride, flexing at the beach for the ladies