Injection Issue/Air Bubble in Mold?

[BMSmock]

Hi there! I am new to this site and making my own soft plastic lures, so please excuse me if this might be a silly question/issue. I have done my fair share of browsing this forum (among others) and watching youtube videos of course (many on the MakeLure page). 

I recently made a cast aluminum mold using Alumilite Vac-50 to replicate a shad swim bait that I typically purchase. I wanted to create this mold with a slot for the weighted hook, so when the bluefish tear it up I can reuse the weighted hook by pouring my soft plastic around it in my mold. I attached a few photos of the mold box I created to pour my cast aluminum mold, my final cast aluminum mold, and my final product with the defect that I am trying to troubleshoot. 

To give some background information, I tried about 10-15 injections and every single injection came out like the one shown in the photo (with half of the tail missing!). I tried a couple injections using the Do-It brand Essential Plastisol, but as not to waste all of my product on practicing my methodology I started melting down some old Senkos I had lying around. I am heating my plastisol/old senkos on an induction hot plate with a porcelain coated steel pot (I wanted to use a microwave but I am currently having trouble obtaining one at the moment). But the hot plate/porcelain coated pot seem to be working okay, the batch heats uniformly without any scorches/burns, at around 350-375 F to a runny liquid that I can easily pull into my injector (I pre-heat my injector by keeping it on a metal grate on top of an electric heater). Once pulled into my injector I tilt it upright on an angle to burp any air bubbles. I inject slowly and steadily into the clamped mold until the material starts to run out of the small exit gate on the tail side of the mold. I then give it some time to cool and open my mold to a decent enough replication of the desired shad lure, EXCEPT for this void space on one half of the tail! Every time. The heated liquid is definitely making it to the tail because half of it is there! It's not like the material is cooling and cannot make it into the tail (right?).

 

Things I tried to remedy the issue: 

- Once the material starts to run out of the exit gate, I plug this hole, then inject a little more material, unplug the hole, inject a little more material, etc. As to not create a vacuum in the end, but also try to fill this void space.

- I also tried pointing this exit gate downwards as I injected to try and get the material to settle into the tail.

- Lastly, and this KIND OF worked but not too great, I poured the soft plastic into the tail and let that dry. Then made my injection to the rest of the lure body. This created a 'cold seam' at the tail and just did not look very 'clean'. 

 

Things I am considering trying:

- Making my injection with the exit gate pointing upward.

- Lastly, permanently plugging my exit gate hole and relocating it to the bottom most part of the tail ('the deep part of the mold', if you will). This will be in an effort to let the entire tail fill up before it exits my mold. It almost seems like I am creating an air bubble in this part of mold by having the exit gate above that tail 'pocket'.

 

I apologize for the dissertation and any incorrect jargon/poorly phrased explanations! Any insight, advice, or general comments would be much appreciated! (Photos are attached)

[MEL]

I would drill 2 small vent holes [#58] on either side near the end of the tail.  They may have to be cleared with a wire

after each injection.   MEL