High RPMs at speed

[General_01]

I have a 383 that is bored and stroked to a 496. I recently went up to see my family. My wife drove her car and led the way. She has a new HHR. She drove it at 65 mph on cruise control the whole way. My tach read 3500. I went to this website ( http://vexer.com/68rt/speed.html ) and it shows I should be at 3100. The car has a 3:55 rear end and a 4 speed and the tires are 235/60/14. I am pretty sure the tach is good. Does this look normal to you guys?

[firefighter3931]

Dean, have you changed the speedo gear in the transmission ? 

Maybe compare it to a GPS if you have one available. 


Ron

[General_01]

Ron, the speedo gear has not been changed. That's why my wife was leading the way. The speedo was reading about 82 mph. You may be right though. I will probably borrow my cousins TomTom to recheck it. Maybe my wifes speedo is off. 

[c00nhunterjoe]

i have 275/60/15's on my car with 4.30 gears. i verified my speeds with gps and i come out with this-
2000 rpm- 40mph
2500 rpm- 50 mph
3000 rpm- 60mph
3500 rpm- 70mph
4000 rpm- 80mph
4500 rpm- 90mph
5000 rpm- 100mph
5500 rpm- 110mph
6000 rpm- 120mph
6500 rpm- 130mph

and i stopped there as my bottom end is not balanced. the numbers were give or take a mph or 2, but that was about the avg. your 235/60's are very short tires, and also very skinny....lol.