Alvin,
If it was compression that was stopping the motor from starting the starter wouldn't just spin. It would just sit there and burn up if you never turned the key from the start position. It sounds almost as if you may not have the correct snout on the starter and it is just barely engaging the flywheel. Either that or your flywheel could have some teeth missing and when the starter gear gets to that spot it would just spin. I am running 11:1 in both of my cars and have no trouble at all. In one car I have a gear reduction starter and the big block has the heavy duty starter that came from Ford. Pull the starter and look at the gear teeth on the bendix. If they show any sign of strange wear, such as just at the very tip, then you need to check for a different snout. If the starter looks ok, check the flywheel for all the teeth.
Ron
