anyone on here have a similar problem with 454 popping at 4000rpm? Over the winter we did oval port heads bigger valves a mild cam(flat tappet) and an intake took the engine to the dyno and it ran great making pretty good hp and excellent torque. Now put the engine in the boat and get a popping sound so I changed the fuel pump to a larger one tried a different thunderbolt distributor and still at 4000rpm it starts. The engine runs perfect all the way up to 4000. Open to all suggestions thanks guys

Yes it’s quadrajet carb

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might of worn camshaft lobe off on an exhaust.

Hope not the cam we put it on the dyno to break the cam in property had it out a few times doesn’t seem to be getting worse if it were a lobe I think it would?

What spark plug wires did you use on dyno? Check them with Meter

Sierra wires what kind of reading should I get with a multimeter? Set on ohms 2860ish?

just start checking them look for one that's out also look under cap for a crack between posts. Double check fireing order.

I did do a new cap and rotor there was some carbon tracking in the cap not sure if it was from running last year or not. Anyway changed it out and still no different