I never ran a SBM , my youngest son had a 93 360 Magnum block break #1&3 cylinders split and #2 Main cap pulled from the webbing, the top of the main stud on driverside still had part of the block around it. 392 (4.00X3.90) Ci 360 with 3 plates NOS I think the heads were edelbrock...I think it was a bad casted block,he thinks it was the power level... The 340 block(I think it was a 68) had the mains walk around a few times.but he never broke that one. that was a 392ci(4.06X3.79) with Shady Dell Brodix and 2 plates of NOS