MSD modules vs. tach readings

I have a msd 6AL box with a 6000 rpm module in it.
Engine runs good till about 5500 rpm on my autometer tach, then stumbles its firing.
If I take out the module,the engine revs past 6500 rpm no problem.
The question is which is the most accurate RPM reading, the module or the tach?
Anybody else had these differences?
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You could take it to the dyno shop to compare.
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i got the same box and tach and i dont have that prob

Mine does that too. AutoMeter 5" tach with 6AL box....stutters at 7200 when it's got a 7500 chip in it. I just put a 7800 chip in it and it's good to go.

My Ford Motor Sports tach is off 600 rpm, found out on the dyno.

Its made by autometer.
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I have had similar experiences with tachs not agreeing with MSD and would tend to think that tach is wrong.

Most tachs are off, some more than others. Dyno'd a Nova a few years ago & the big $$$ Autometer was 1500 rpm off!
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Mine is off as well, but according to Autometer, just send it in and they will re-calibrate it for you.
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Mine has a strange misfire @ 7500, come to think of it. Got a 8k pill in it. Think this sunday I'll pull that out and put the 9 in, and see what happens.

(sometimes it's the simple things)..........[img]/phpBB/images/smiles/icon_rolleyes.gif[/img]
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I've got a 6000rpm pill in my 6AL box and when I rev it to 6k rpm, the Autometer tach is dead on when the it starts cutting out.

Good Luck