Is there any advantage/disadvantage to swapping out a stock cam in a 1999 454mpi for a stock 454mag cam? Would anything else need to be changed? ECM remapped etc??? A friend is pulling his motor to replace a worn coupler, gimbal bearing and has access to a Mag cam and thinks he might get a better sounding and slightly better performing engine?

I pointed out to him the cast internals and small heads and suggested swapping his stock exhuast for EMI or similar if it is "sound" he is looking for....

He realizes the 454mpi is cast internals and small heads etc.......but budget dictates any mods.... he thinks it is the MEFI 3 ECM but neither of us is sure and do not know if that would need to be re-mapped? Thanks for any input..........

The ECM would need recalibrated.

Thanks, so with just a swap of cams without an exhaust upgrade a recalibration is needed, or is that with an exhaust upgrade as well as cam that a reflash is required?

I have done a bunch to 502 mpi's...

For what u would get it's not worth the trouble. I would never ever recommend installing a cam without doing cam timing. ESPECIALLY in a boat!!!!....It can be hard to accept that it takes huge HP to make small changes in boat performance. Doesn't stop people from trying tho...

Adding exhaust by itself won't need a recal. Switching the cam with or without exhaust will need a recal. I also do not feel either is worth the effort or expense on a 454mpi. You might gain 20-30hp total or 1-2mph.

Point taken, it is a good friend's boat and when he asked me I wasn't 100% so thought I would get some knowledgable opinions..... I will tell him to keep it stock, save his pennies and keep his eyes open for a swap in replacement..............