How accurate is the stock tachometer? I have a autometer shift light and I have the pill for 5800 inserted. But when the light goes off, the tachometer in the dash reads lower. Which one should I believe?

The shift lightis hooked up to the white wire that feeds the tach.

Steve

 

a light will always respond quicker than a tach needle. Factory tachs are pretty accurate but sometimes a bit sluggish. I don't mind the stock tachometer, but your shiftlight is probably reacting quicker than your needle.

 

I would tend to agree that the light is a bit closer to the truth then the stock gauge is.

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

Do you have a V-6?
I'm looking for a V-6 factory tach.
How much off is the tach in the dash?
It shouldn't be off at all.
Ask Autometer for their input.

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Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

the movement of a stock tach isn't regulated like aftermarket tachs are. That is why stock tachs tend to read over the actual rpm when you rev quickly. All in all the light is more acurate than your stock tach.

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'88 Mustang Gt Nitroused 351w/c4

 

i found that my factory tach was off by 100rpm at 5000rpm then i hooked up my autometer

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The problem i am having is the factory tack is slow. By about 2000 rpms!

I switched over to a solid roller cam and the motor revs REALLY quick. Anyway, I have the autometer shift light with the 6600 pill in it and when going through the gears, that light comes on when the tach is only reading around 4500. You can tell the motor is going faster than that.