Singer 236G131 Post Bed needle won’t pick up tread from Bobbin

[Rogueshoemaking]

Where would I find an engineers report to set the needle bar height to its correct position, 

I know the hook has to sit 1/8 above the eye of the needle, so 3.38mm. 
But does it change things if the needle bar is out of whack, can I just move it down to the correct height, below the hook, and everything else should work accordingly. 
 

I have the 134 LR needle back in. 
it can’t be the tension, and I’m running out of time to get this project done. 

Just now, Rogueshoemaking said:

Where would I find an engineers report to set the needle bar height to its correct position, 

I know the hook has to sit 1/8 above the eye of the needle, so 3.38mm. 
But does it change things if the needle bar is out of whack, can I just move it down to the correct height, below the hook, and everything else should work accordingly. 
 

I have the 134 LR needle back in. 
it can’t be the tension, and I’m running out of time to get this project done.