i'm running a 502 motor in a 27ft. formula. motor has roller cam and roller valve train, also stainless marine exaust,adjustable fuel reg. b&m air intake,re-programed ecu. problem is engine tops out at 4000-4200 rpm. runs strong to that point then lays down. throttle working o.k. but seems there's about 1/4 throttle left with no additional rpm. any help appreciated,can only afford to do my own work. tommy.
If you have already changed fuel filter(s), hang a pressure gauge on the fuel rail. Sounds like loss of fuel.
The inlet to the pressure pump is known to get clogged. If it is anything like the 496s, there is no filter before the pump.