I have an '85 F150 4x4 with a 300 IL six. I've calculated the red line at a conservative 3500 rpm. Can I run it at 2800 or 2900 on the interstate without damaging the engine? Otherwise, I'm stuck at at about 63 mph.
How in the world did you ever calculate the redline at 3500 rpm. That sounds about 2000 rpm too low.
According to what I've found (on the internet), you don't want your piston to travel faster than 4000 feet per minute, but that's for a "street engine" not a stock engine. The formula is RPM x Stroke / 6 = FPM. The stroke is 3.98. 3500 x 3.98 = 13,930. 13930/6=2,321.6 FPM. Sounds like I can go a lot higher? 5000 RPM would give me 3,316 FPM. But here's the kicker: Although it will go up to 3500 easily, it really quits pulling hard at 3000. That's why I set it low. Going past 3000 is scary. And just so you'll have some context, I have dual Weber 38/38s on a Clifford intake (780 total CFM), and EFI exhaust manifolds off a '91 F150 (fuel injected). No need for headers unless I'm going to cam the engine. I've heard that these motors were used in generators and ran a constant 3000 RPM. But those motors were detuned to about 88 HP. So, I have enough information to be dangerous. I really don't want to blow the motor. Any suggestions?
You might want to set your ignition timing for best performance. Do it the European way, advance the timing 2 degrees then go out and accelerate. Keep doing this until it starts to ping, then reset the timing back 2 degrees and it will be at optimum for the modifications you've done to the engine.