Ok, I have a mildly built small block that is a fairly recent rebuild. I put the motor in last year, and it ran like a bat outta hell. Ran it for 500 miles, went to adjust valves and changed oil. Went to start and ran like it was missing on several cylinders. Changed out lifter, plugs, pushrods, and rocker arms. Ran compression, 150 per cylinder all 8, checked spark, all spark hot and good, got fuel. Set everything up, went to start and had distributer as far as it would go and to to pump gas to keep running. Rotated 180 and wouldnt even start. Any ideas would be very helpful.