92 bird 108,xxx 305 automatic completely stock. only had a couple weeks.
cruising at 55 mph the tach reads 1300-1400 rpm. it just seems low to me

 

What does it read at idle? That will, most often be your tell tale sign of a bad tach or the likes . Our car were made with notoriously bad tachs. I had to replace two on the two f-bodies i owned. My 83 t/a read 3 grand at idle, and would sweep the whole gauge, in every gear when i was really around 3-4k. I heard that there is a resistor behind, that goes for a nominal fee of like 2 dollars or so that u can replace, if thats the case. First, try unplugging, and replugging in the tach wire to the dist. or coil. just to make sure the connection is good. U didnt give enough info for me to give u any other scenarios
Jim

 

What are your rear end gears? If you're running, 2.77's, for example, that range might be about right.

JamesC

 

i don't have any other problems w/ the tach. it idles at 500-600 rpm. at 70 im running about 1700-1800 rpm.

 

That sounds right to me also. The overdrive helps keep the rpm's low when you are going 55 .

 

With 3.23's, my car runs about 2300 at around that speed. I'd say you have highway gears.

JamesC

 

I think your in the clear that sounds about right it may be a tad low by about a hundred revs or so.

 

If factory tachs are within a 100 or so, they're probably doing darn well.

JamesC