Would you like to know if you can run a 3hr.30 min. marathon? One general way to find out about what your marathon speed would be is to run a bunch of 800 meter runs (twice around a standard outdoor track) in an average of 3min.30sec. each, if you think you can run a 3hr. 30 minute marathon.
Between the 800s, jog for the same number of minutes it took you to run your repeats. If it took 3 minutes and 30 seconds then jog an easy recovery pace for 3 minutes and 30 seconds not worrying about how far that takes you. This will give you some of the necessary speed training and a general idea of the amount of speed you have to run a specific time in a marathon, in this case a 3:30 marathon. If it takes you an average of four minutes for the 800 meter runs with four minutes recovery jogs in between then you have the capacity for a four hour marathon.
Of course there are other factors involved in completing the marathon in this time or any other time. You must do regular marathon training, endurance runs, etc. along with these regular workouts or similar types of speedwork. You can find inspiration, motivation and more specific advice in my marathon training guide called, ‘Seven Steps to a Successful Marathon.’
My runner friend begins running his Yasso 800s a couple of months before his goal marathon. The first week he does four. On each subsequent week, he adds one more until he reaches 10. The last workout of Yasso 800s should be completed at least 10 days before your marathon, but 14 to 17 days would probably be better. He also suggests that the rest of the time just do your normal marathon training, paying special attention to weekend long runs. Give yourself plenty of easy runs and maybe a day or two off during the week.