I have a 67 barracuda With a 318, 904, 4.10 gears...
Running a 25" tall tire...
At 60 mph I calculate my rpms to be 3300....
My tach is reading 4500-5000 cruising around 50-60mph...
The tach reads 3500rpm when I am going 41mph...
I know this is way off.... What could be the...