So, I finally got something done this weekend on both of the engines.
I went slightly off instructions, as you do, so that I could compare the engines as sub assemblies. There are quite a few differences but I will discuss each engine on its own before moving to the comparison.
The IBG Engine.
The IBG Engine is spread across a couple of sprues (G and H) along with 2 pieces from the PE Fret, notably a bracket and the cooling fan. It's a pretty simple affair and on its own it looks like quite a decent shot at an engine. However, once compared to the Thunder Models engine it does look to be a little bit simplified due to the lack of some details and some of the pipework. More of that later.
The IBG plastic feels a bit soft and when cut with sprue cutters doesn't give that satisfying click like perhaps Tamiya plastic does but otherwise its fine to work with, sands well and I had no problem with the liquid cement I use, Slaters MekPak. The PE is good, bends well and is quite sturdy. The lack of detail on the fan stands out a bit on the PE but one is unlikely to see much of it once the model is complete even if the engine panels are left off the model.
The instructions are clear, there weren't any issues there at all and I do like the fact that the completed assembly at the end of each stage is shown, I think thats a very nice touch that other manufacturers ought to copy if possible.
Altogether not bad and looking at the references it looks to be pretty accurate other than some of the simplicities.
The Thunder Models Engine.
The Thunder Models Engine is spread across quite a few sprues (A, B, C D and E) along with 2 pieces from the PE Fret, a filler cap and the cooling fan. Compared to the IBG engine it is a lot more detailed, and seems to have more detail in that the parts themselves seem to be more intricate. The engine is also broken down into smaller pieces, with the engine block being 7 pieces compared to the IBG one which is 4. All in more detail and more intricate than the IBG one.
The Thunder Models plastic is harder, perhaps more brittle and when cut with sprue cutters it does give that satisfying click, it also sands well and I also had no issues using MekPak. I did manage to snap the fanbelt (and a piece of it was claimed by the carpet monster whcih I will need to fix. Its clearly visible in the phot'o's here. The PE is a little thinner and more fragile than the IBG etch. It bends well but feels a bit flimsy. There is also a lack of detail on the fan so maybe this is just what the real thing is like, though references seem to show otherwise.
The instructions are pretty clear though I think not as good as the IBG ones. I think they could, in something that could be as complex as an engine, be a little more clear in places. It's a small issue but given the number of pieces I think they could have put them all on a couple of sprues like the IBG one, even with more parts in play here. It's a personal thing but jumping between sprues for small fiddly parts is slightly annoying. Someone with a small bench and limited space may get a little annoyed by the back and forth between sprues.
What I like the the IBG model is lacking is the callouts for paint by Thunder Models. They are all MIG colours and there is no conversion chart but this shouldn't be too difficult to convert to your paint preference.
In summary then the Thunder Models looks to be more detailed and accurate than the IBG one and is less simplified but spread across more sprues and has less sturdy PE.
Side by Side
When the engines are seen side by side the differences are really easy to see. The Thunder Models engine looks much more impressive. The other surprise is that the Thunder Models engine is also larger, noticeably so when side by side. Which one is correct i do not know as the references I have do not give dimensions for the engine itself. They may be different engines, though I doubt it given the similarities, even when taking into account the difference in detail.
With respect to detail its a clear win for the Thunder Models kit. However, the IBG kit has more sturdy PE and for those not bothered about displaying the engine is probably good enough. In my case I want to open the IBG engine up and close up the Thunder Models one which had me thinking of swapping the engines between kits (to have the mode detailed Thunder Models engine in the IBG Tractor) on show. However, the size difference may be an issue there so some detailing of the IBG engine, using the Thunder Models one as the reference may be on the cards.
Hopefully that gives everyone an idea of what it's like so far. Neither kit so far has major issues, other than losing some of the fan belt on the Thunder Models kit, which I'll probably remedy at some stage.
More to come soon I hope with the Chassis and suspension to come before the builds split when the Tractor gets its crane and the Transporter gets its trailer turntable fitted.