I have an 86 F-150 and just got an aftermarket tach for it. I was wondering what rpm should i be shifting at. I have been shift at 2000 is that to high or to low.

 

Here you are: probably more than you want to know or hear, but hopefully this'll help. My owner's manual ('95) gives shift points in mph. But these seem extremely low and probably relate to advertized fuel economy ratings, which harldy apply to real world driving. Instead of shifting all the time at 2000, why not just shift by feel? I would feel extremely restricted if I limited my motor to 2000 RPM. Given that the HP peaks at 3400, I am sure it is good for at least 3400 RPM. I believe Pitt Electric (check on web) lists the 300-inch six (they use it in generators) as having a maximum sustained rpm capability of about 3400 or 3600. Also, I think the shift RPM likely increases as you move into higher gears because your load increases with speed and your rear wheel torque decreases as you move into higher gears. I recently read a racing tip that said a good rule of thumb is to shift so that you enter the next higher gear at the engines torque peak, which for my 300-inch I-six (and probably yours too) is 2000 rpm. That's good for moving out fast as I notice with mine that as the tach reaches 2000, there seems to be a power surge that continues on up the rpm range at least to the mid 3 thousands. By the way, I had an '84 300-inch six and would at times rev it to 4000, but never more. I have run my '95 to 4000, but think that 3600 to 3800 would suffice when in a hurry.