Mercedes DIII Engine

I was recently sent some old William Wylam drawings of several engines by Stephen M (long story) so I have been spending some of my spare time drawing up the Mercedes DIII engine in 1/5 scale. The Wylam drawings were pretty good so I've got the engine reasonably well detailed and have done a couple of check prints to see how well it would come out. After doing the prints, I made a couple of changes to the .stl files (for example, I split the inlet manifold into two parts to improve the surface finish) and added infill to all the prints so that the top surfaces didn’t “collapse”. Inevitably, this increased the weight slightly.
The entire engine would be too big to put into a model since it would take up the space where the motor, battery and esc would sit but I modelled it all anyway. There are also problems printing the crankcase and sump unit unless they are printed with a lot of infill. The entire printed engine would weigh around 250grams and this is too much weight for