why won't my engine turn?

What method did you use to "flushed out oil "? Remove the spark plugs. Squirt a little oil in each cylinder and try turning the engine over by hand to see if it moves in either direction.

I just flushed oil out of engine block, haven't touched spark plugs

I agree with 10speed, but you will probably need to be prepared to do some lower end repairs. Once gas gets into the oil system, it acts as a real strong detergent and will totally remove any lubricants from the pores in the rod and main bearings. Depending on how long the gas was in the engine oil while running will determine how severe the damage will be to the bearings and crankshaft. If the engine doesn't turn with the plugs removed, you will need to drop the oil pan and start to loosen the rod and main bearing caps. Try to turn the engine over with a socket and ratchet on the crankshaft pulley after you loosen the rod and main bearing caps one at a time. Remember; if you remove the caps; they will need to be marked and be put back on the same crank journal the same direction, and be torqued to O.E.M. specs. Good Luck!.

thank you all you guys for your advise, was very helpful, it all made me do a more thorough check on all engine and found a small crack in one of the ports in the head, so I dismounted it and it was small enough to weld and re-machined, fortunately I am an engineer and have a excellent machinist that does exceptional quality work and except for cosmetic work which is next project, the car is running like new now it had only 30,000 original. Thank you all again,