Anyone out there know what the Full advance is supposed to be on 98 454mag MPI's? I guess max without causing any issues???? I would like to check
Thx.

Depending where base timing is set total timing ends up around 36 degrees in the higher timing tables at 50-70 map, Smitty

If its a stock engine, just set it at 8* in base timing mode and be done. Another 2* might be good for another 0.3mph and not worth it.

I'm used to non computer motors. Is a jumper or something that needs to be done to the computer to put in a certain mode?
Thx

There is a diagnostic connector close to the ECU on the port side of the engine. You need to remove the plug end and jump a and b pins, bring rpms to 1000-1500, otherwise it jumps all over, then set the time with the timing light. Merc makes a tool that you can plug in for $10-15, 805747A2

Cool that's what I needed thanks

last question,, if bringing it up to 1000-1500 rpms to set initial 8*
Wont that speed (1000-1500) start bringing in advance or is that what the tool is doing is stopping any advance?

no, the jumper locks the ECU from changing the timing. The timing won't move even if you rev it up to 3000rpm. One other thing, mine does not idle very good and will die at idle sometimes when the jumper is in, so just rev it up and set the timing.

Thanks