Enginetech BB638JSTD ROD BRNG CHRY DODGE 3.3L 201 3.5L 215 3.8L 232 Due to the new advances in aluminum-silicon bearing technology Enginetech is converting most of our main & rod bearings to the advanced aluminum-silicon material.The performance of new aluminum-silicone alloys is now equal to or better than the original tri-metal designs.The additions of high amounts of silicon dispersed within aluminum alloys have moved aluminum-silicone bearing material to the preferred bearing status.Enginetech main & rod bearings – the choice of rebuilders for over 25 years. About ten years ago, when aluminum bearings were first being introduced, Enginetech continued to produce the higher quality tri-metal 780 bearings. Enginetech stuck firm with the 780 tri-metal material for years because it was far superior to the early aluminum bearing technology.