I’m working on a new X-carriage for my QU-BD nozzles for the OB1.4 printer by Wired1 on Thingiverse. I wanted to give this 1.75mm extruder a second chance after my first experience ( http://www.jonshobbies.com/troubleshooting-my-qu-bd-extruder-head-jams.html ). In the end I think a majority of the problems were due to a cheap PID controller from eBay which was not accurate on temperature readings. Once I finish the X-Carriage design I just need to change out the 24v heater core for a resistor with some aluminum wrapped around it and install a thermistor and I think I’ll be printing PLA alright. I used this extruder to print my first dedicated 3D printer, but it took a long time and a lot of failures, here’s to better success.
Looks good, I notice the little blocks inside the bearings are gone 
Yeah the piece holds the bearings fairly firmly. I don’t see any reasons for the blocks, if they slide one way, they’d slide the other way as well so only blocking one end would be futile in the case of a bad bearing fit. One problem I realized with printing this incomplete model is that the tabs that the QU-BD gets mounted to actually rotate up a little when the bearing is inserted, causing it to no longer be at a flat angle. I need to go get a protractor and find out how many degrees it’s off then modify the design to have those tabs at a negative angle so when you put the bearing in they will sit straight, either that or just use some shims 
Dont go the shim route. It doesnt last.
I finally got my QUBD extruder working properly by making this easy PTFE barrel mod. Check out my step-by-step tutorial here http://www.mastersketchup.com/qubd-extruder-jam-fix/