What would have caused this?? I pulled this quadrajet off a customers 87 dolphin motor home with a BBC 454. The only guess we had at the shop was because the heat riser valve was a bit rusty and stayed close while he was pulling a hill. This would cause a tremendous amount of heat to travel through the intake manifold. Any other thoughts?? We did get it running again with the 850cfm q-jet off my truck. Ran great actually.