Ok, crazy idea, I have a 351w cam which we all know is the same design as a "H.O." block. I'm putting it in a 91 block that is going to be carbuerated. Ok, here is the weird apparently never asked question...... Can I run the stock hydraulic roller lifters with the flat tappet designed cam? All I can find in the differences with the roller cams in comparison to the flat tappet cams is that the roller cams have a longer duration since the roller is more accurate. With this being the case I see no difference in running a roller lifter on a flat tappet cam. I can see the bad side of running flat tappets on a roller because it would try to cut into the higher lobe but I really don't see a downfall to what I'm proposing, obviously the only advantage is that I won't have to buy a new set of flat lifters although they are cheap, but I figure the rollers would reduce friction and maybe add a few horsepower. Ok, any ideas or if anyone has seen this done or done it themselves please let me know.....