28* initial timing for a 318? How can that be?

Newbomb Turk said
Is the choke holding the throttle open all the time or is the throttle open that far all the time?

If it is, you need to close the throttle down and make it idle with the throttle blades above the ported vacuum hole at idle.

Plus, if you have the throttle that far open it’s pulling fuel off the T slots as well as the idle circuit.

On my bench test I even backed the curb idle way off the cam. the notched choke cam at full open choke will not fall off that last step keeping the throttle blade from closing all the way and giving the square transfer slot.