So if I wanted to make a replica of an F-14 it'd have a max speed of 8/12 it would have a thrust rating of 4/6? Is that right or is jets have a top speed?
Thrust 4/6 would give it 4 regular or 6 'full burn' points to move per turn. Assuming you take off at safe and climb to ceiling then start to accelerate you will start off moving at 2 aero (32 ground) and gradually accelerate as you climb (assuming 2 levels/turn) by 1 aero (16 ground) unless you throttle back or climb faster. If you dont then you will reach 3 aero (48 ground) and stay there. Assuming you climb for 4 turns (to height 8) you will be going at speed three, then you level out. With no other altitude changes and going at full safe burn you will reach Speed 8 (128) in three turns and be able to maintain it easily, unless you climb or perform a maneuver that costs thrust.
Now, if you hit full burn once you level out you will jump straight to 6 (96) on turn one of leveling out, 10 on the second and then creep to 11 before finally hitting 12 on the fourth turn. At that point you are burning fuel rapidly though, and will lose speed on any maneuver that does not cost you at least 3 altitude.
4/6 is good enough for a "modern day" conventional fighter, but do not expect to be outrunning a later design (Although you could out punch them).