440 Won't start syndrome

I have a similar problem with a 383 :banghead:
Sorry to hyjack the thread, but it looks like a similar problem so it might help both of us
Does yours do this

[ame="http://youtu.be/w50TpfQhVoM"]http://youtu.be/w50TpfQhVoM[/ame]





It tries to start, but when you let go of the key it stops and "tries to run backwards" spurting fuel out of the carby.
This is a 2nd hand engine with new intake, so I havent had it running before.
Had timing cover off and dots line up on timing gears, looks reasonably new.
I have tried 3 different carbys. 2 x edelbrock750 and 1 x holley 850 with the same results.
Tried a different fuel pump - same problem
It has a new hei dissy, new leads, new plugs, new mini starter, new coil, new battery.
I have checked timing at TDC with piston, spark plug out.
Checked rockers all moving nicely
Compression test 115 all cylinders
Time for help.

Dave