one else has directly answered your question about determining the red line,
red line(the rpm level you should not exceed without expecting to eventually do damage to your engine, this does not mean you can run at red line without problems, it means if your STOCK engine gets to that rpm but rarely it should be ok.) It is determined by the weakest link in your engine (usually rod bolts, or main cap bolts streaching enough for a bearing to spin) mostly by two factors,critical piston speed and valve float rpm, your engines RED LINE is just below which ever one is reached first. now valve spring pressure, lifter type, (hydrolic flat tappet,solid flat tappet ,mushroom base flat tappet,hydrolic roller, solid roller )lobe profile on your cam and valve train weight , use of rev kits etc. and harmonics determine valve float, but on stock engines useing roller or flat tappet hydrolic cams about 6300-6400rpm is going to be valve train red line.
piston speed is about at a reasonable max with stock components at 4000 feet per minute, now rpms alone do not have as great an effect as stoke x rpms in figureing piston speed.
example 4000fpm(feet per min.) is 48000 inches per min. if your stroke is 3.48 like in a 350 chevy the piston must go up then down in each dirrection once for each rpm(revolution per min) so 3.48x2=6.96 so 48000/6.96=6896 rpm, in this case the valves are more likely to float before the rod bolts snap from inertial stress, but lets try a 383 that has a 3.75 inch stroke,3.75x2=7.5" so 48000/7.5=6400 rpm max for the rod bolts(about the same as the probable valve float rpm.
btw long term highway cruiseing speeds should be kept to 2000fpm piston speeds for best engine life.
and yes I am well aware that some guy at the track regularly turns 7500rpm with his 350 chevy,STRESS IS CUMULATIVE ,ITS JUST A MATTER OF TIME BEFORE SOMETHING SNAPS,A VALVE FLOATS ,A VALVE SPRING BREAKS ETC. AND THE MORE TIME YOUR ENGINE SPENDS AT OR JUST OVER THE RED LINE THE GREATER THE CHANCE SOMETHING EXPENSIVE WILL HAPPEN!
