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Tach it on the wall!

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kodanja

kodanja

Obi Wan
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Ok I timed my car today with a state of the art Snap On tool timer its was reading my idle at 750 and my tach was reading 1k :wall:

I rebbed it up to 3k on the tach & it was reading only 2300 rpm on the timer WTF@!

Is there a way of calibrating my stock tach or do I need to upgrade?
:nopity:
 
Bill,

Before you go nuts, what kind of wires do you have on your engine? I cannot get an accurate reading with my Magnecor wires on either my Snap On, Equis or Craftsman timing lights.

Get a plain carbon filament spark plug wire at NAPA and use that for #1 cylinder and I'll bet you'll be fine. Nothing fancy, just a Chevy V8 spark plug wire.
 
The stock mechanical tach can easily be wrong by 500 rpm or more. If you want to take a stab at calibrating it yourself, start by reading Tony Rhodes' speedo article (the tach is just like a speedo except without the odometer/trip meter). Or there are several shops around that can do it for you.
 
I think I'll bring it to a shop. That way It's done correct the 1st time....

thanx
someday ill even hookup the speedo cable.... :wall:
 
It's amazing how much a mechanical tach can be off. It is worth having them checked.

Assuming your new timing light/tach uses an inductive pickup (and I can't imagine that it doesn't). Also check the "direction" of the pickup. If you look at the pickup and/or read the instructions you might find that there is a specific side that is supposed to point towards the spark plug. Some of my equipment has arrows on the pickup that point towards the spark plug. If I hook that equipment up backwards I can get erroneous readings or no reading at all.
 
Yup, It was pointed in the correct direction....

I one of my past threads I stated that I was hitting 70mph at 33rpm, In reality I was probably only turning 27ish rmp's
 
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