Stock Tachometer

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Aug 27, 2007 | 03:57 PM

zacharyhorn

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Joined: Oct 2005

Posts: 809

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From: Greenville WI

Car: 91 Firebird

Engine: Turbo 355

Transmission: T-56

Axle/Gears: 3.73:1 7.625" 10 Bolt

Stock Tachometer

How far off is the stock tach usually? Read fast or slow? J/C.

Aug 27, 2007 | 04:09 PM

SpitotRs305

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Joined: Oct 2006

Posts: 1,974

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Car: 91 RS

Engine: 350 vortec

Transmission: T-5

Axle/Gears: not the best not the worst

Re: Stock Tachometer

dunno mine was off about 500-600 rpms higher than actual

Aug 27, 2007 | 07:43 PM

Sonix

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From: Calgary, AB, Canada

Car: 1982 Trans-Am

Engine: 355 w/ ported 416s

Transmission: T10, hurst shifter

Axle/Gears: 10 bolt, true-trac, 3.73

Re: Stock Tachometer

I'm pretty sure mine is fairly accurate. Maybe i'll hook up a spare I have laying around in parallel to find out...
I'm pretty sure at idle it's accurate, and at ~3000RPM cruise...

Most people say their tachs read high though, something in the range of +/-10%

Aug 27, 2007 | 07:46 PM

sofakingdom

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Car: Yes

Engine: Usually

Transmission: Sometimes

Axle/Gears: Behind me somewhere

Re: Stock Tachometer

They seem to fail by reading higher..

All of the ones I have read high. The one in my car is the least high, at about 3-4% (or was when I put it in at least..) I have one that's 100% high (reads twice actual RPM).

It's meaningless to talk about "xxx RPM off". That's equivalent to having the pointer installed wrongly on the movement. They don't go bad that way. Rather, they read a PERCENTAGE off. So it might be 100 RPM at idle, 250 RPM at cruise, etc.