put it at tdc on compresion stroke and tighened till the pushrods stopped turning then another half turn like the book says
Did you put it TDC on each cylinder and made adjustments? Is the cam Stock?
theres a 100 ways to do it, I was taught to Starting with #1 cylinder, turn the engine over until the exhaust pushrod just begins to move up. At this point, stop and adjust the intake valve on the same cylinder.
tighten/loosen the rocker arm til the pushrod is at zero lash meaning you cant wiggle it up or down between the lifter and the rocker arm or some people spin the pushrod with there fingers and tighten/loosen the rocker til they feel a slight resistance and then tighten the rocker another 1/4 to full turn depending on your application.
then You will now want to turn the engine over while watching the same intake pushrod that you just set, it will go full open and then begin to close. When it is almost closed, stop and adjust the exhaust rocker arm on that particular cylinder. By following this procedure, you are assured that both of the lifters are at the base circle of the cam and that there is no additional pre-load applied to them from cam lift at this point.
what worries me is you said "tighened till the pushrods stopped turning" thats way to tight.