k b 7.5
Is your engine drum rotor or disc rotor? If its a drum and you have disassembled it recently check to make sure the front housing is installed correctly. My 7.5 has billet alum. front housing, which has a flat machined on inside portion. That HAS to be installed up towards bottom of piston,otherwise piston hits frt. housing. Hope this might help.
If its too slow you need more nitro!!!