According to the instructions that accompany the S-Helper Service NW2, the exhaust stacks are easy to exchange. However, mine wouldn't budge. Over the years of owning it, I've tried but they just wouldn't give. When I asked about this issue on the Yahoo! S-scale discussion group, all replied, including Don Thompson, that it should be a simple pull-up-type of event. Although Don said that it could have been that some eager-beaver on the assembly line had applied some glue. So, more drastic measures were required, since by now I was determined to replace the stacks. I wrapped the teeth of a pair of pliers with some cloth and pulled on one of the stacks with a lot of force. The entire roof section with the two stacks popped off, as you can see in the photo below.
In the center of the next photo is the part I pulled off. The box comes with two additional types of exhaust stacks. As can be seen in the "Prototype Information" page, the prototype photo of engine #3909 shows two short, stubby stacks. That's how EMD designed and made them. The problem very quickly identified was that the exhaust smoke either blocked the crew's field of view or they would wound up inhaling it. The longer stacks were used afterwards. Since the S-Helper Service's NW2 is numbered #5912, I presume that the engine has already been upgraded, so I want to use the other longer stacks on my model (the short stacks don't match the ones on engine #3909).
As stated, the stacks on my model wouldn't budge. With the engine cover plate off of the engine, I could now drill out the unwanted stacks. I found a drill bit with the same diameter as the width of the square foundation of the stacks, and mounted it in my drill press. Then with both hands holding the engine cover plate, I drilled out each stack until they popped loose. Although the stacks' foundation was destroyed in the process, the stacks themselves are still intact and could potentially be used again. The cover plate itself was unharmed.
It was then a simple matter of snapping in the stacks that I wanted to use into the cover plate. I added one tiny drop of superglue to the stacks' foundation on the inside, just to make sure that if the engine is turned upside-down, they don't fall out. The cover plate then snapped back into place on the body. Although these stacks aren't a match for PRR #5912 in the 1950s, they do match the other PRR NW2 engines, and #8677 in the 1960s (which is what this engine was re-numbered to prior to the Penn Central merger).
The more I look at this engine, the more I appreciate the fine work S-Helper Service did in designing and having this model produced. The piping, the hinges, the door handles, the nuts and bolts, etc. really add to this model's critical review under close-up inspection. However, similarly, the more I studied the prototype photos of this PRR engine, I noticed a few things that the model doesn't have. I am not going to go crazy with this, but one thing that really stood out to me was the piping and fuel gauge (I presume) above and next to the fuel tank. Since it is an external part, it is actually quite visible in normal day-light viewing. The relevant portion of the prototype photo is shown below, with the parts highlighted by the two arrows.
The model has a pipe running above and behind the fuel tank, but it doesn't match the prototype at all. Also the fuel filler cap is set back a ways. So, I decided to enhance this section of the model.
The photo below shows what I wound up with. I used some scale 2-3/4" music wire, some styrene pieces, and the filler cap from the model's fuel tank (which is a part that is just press-fit into the frame, so it is relatively easy to pop off). Since it is impossible to drill a hole straight through both fuel tank holders/brackets on the model, I just drilled a small indention into the brackets matching the wire's diameter. This allowed me to "sink" the wire slightly into the hole, thereby making it look like it runs through the brackets. The key, of course, is to get the holes drilled at the same location on both sides of the brackets. I was successful at doing it on this one, but not entirely so on the fuel tank on the other side of the engine (this has to be done on both sides of the engine). The music wire piece on the right side of the photo was bent up and attached to the underside of the frame with superglue. I used superglue for everything, except the assembly of the fuel filler gauge. The fuel filler gauge (the white part) I constructed out of a scale 4"x8" piece of styrene in the back (to give the "face" plate something to adhere to), while the face plate was made out of scale 1"x8" styrene. There is a bit of a chamfer where the fuel filler cap sits, angled such that it is easier for the maintenance crew to gain access to it. I filed the chamfer in the styrene back piece, and then bent the 1" face plate with a pair of pliers and used Testors glue to glue them together. The styrene bent well and didn't break. Although it was a bit of a challenge to get those tiny parts to stay together while the glue set. I then used superglue to attach the part to the underside of the engine's frame. I sliced the fuel filler cap off of the S-Helper part using a razor blade, and then glued it to the white styrene with superglue. The middle and left pieces of music wire were cut, filed, and fitted, and then glued in place. There is a hole in the white styrene piece that takes the left music wire. The bottom, back of the white styrene piece was glued to the pipe coming out of the fuel tank, so that there is support for it, otherwise I could foresee it breaking off quite easily.
Here is a close-up shot of the under-construction styrene part, to show you where the chamfer was filed. It is really tricky to get these parts glued together. I used a normally-closed pair of tweezers to hold the 4x8 piece in place, while a no-handle flat file holds the 1x8 piece in place so that I can use my hands to apply the glue. When the first glue-up was set, I bent the other part and then glued it in place.
The photo below, taken from a different angle, might help you see how the parts were fitted together. You can see in the back that the original pipe is still there. It is no longer visible at normal viewing angles.
To simulate the fuel filler gauge, I cut and glued a tiny piece of brass wire to the vertical surface of the styrene part. I then painted the new parts with Tru-color (TCP-075 Pennsy Brunswick Green) paint, which is a pretty good match for the S-Helper body color. The photo below is an extreme close-up, purposely over-exposed to show these dark parts. All-in-all I am happy with the enhancement. It took me a few days of modeling time to do, but it was enjoyable and, to me, it seems to make the model a more accurate one.