Hey guys..

Can someone tell me if it safe to run a 496MAG ECM on a 496MAG HO, and what will happend if i do??

Regards. Jens.

Not to sound like smart azz but their is reason for 2 different PCM's -- your engine will start and run but the fuel mapping among other things that are PCM controlled is a different calibration between the 2.

The 496 Mag vs HO = 50 hp and the 2 biggest MAIN difference between them is the cam and the calibration of the PCM

Get the cam and now you have an HO..

It would be interesting to run the Mag ECM on the HO motor and watch the wideband data.

Yes it would!

I agree. Will the MAG 375 PCM supply enough fuel for the HO at WOT rpm? Sounds expensive.

Might lean out a bit too far..

I'd bet it wouldn't be as bad as most think. Now I'm not implying it would be perfect though.

I was thinking same. Especially since Merc tends to be a little fat with their tunes as is.

I do know this 4 sure - years ago had 496 NON HO and wanted to see if it had a bad computer as the scan would not communicate and the engine would backfire while trying to start, It also seemed like it wanted to run for about 2 secs but completely quit each time the same way.

I had good used spare 496 HO PCM 555 ( switch out for testing ) - the engine started and ran (water hose tested) but as you throttled up and just below over rev limiting you could hear & tell that that fuel delivery was off. Too much fuel and trying to regulate it - the engine became blubbery and started missing. The correct PCM was ordered and bit of other things, it ran like it should of after that. The 496 HO PCM 555 for the Mag 496 never would of had work (UNTOUCHED or not recalled) I do know that 4 sure 100 %.