We had a problem with them when they arrived from Indy that my engine builder had to fix before they were able to be used and I have had a problem with breaking their rockers on three different occasions , I only shift at 6,500 and we aren't running a lot of spring pressure . I understand that was an on going problem with their rockers. Indy no longer makes or offers them anymore they sent me what they had left in stock but they weren't the ones I needed. I ended up driving three hours one way to buy a used set because I couldn't find them anywhere. A friend had one that I was able to get the second time I broke one. I have to go to Harland Sharp, T&D or Hughes to get a complete new rocker system and they aren't cheap. That motor is out now due to a cracked stroker crank and my W2 / 367 back up motor is in now. My ancient W2 ductile iron non-roller rockers have been fine for over 25 years with out any breakage