How do I make my support not suck? And other issues

Bambu Lab Software Bambu Studio
1

I need help getting my supports to not suck…and how to properly scale parts.

I am trying to print my first large (as in number of parts) multi part print and before I even get into it im already having issues. Printing in PETG at .16 layer height.

Years ago, I saw this model and it made me want to get a 3d printer, Ive been printing for a bit now and finally figured it was time to print the model that first got me interested, ericthepoolboys’s working ford flathead engine.

My first issue is when printing the cylinder head, I cant get the support off, and when I do the model surface is terrible. Ive tried increasing Z (started at .166 then .175 then .2), pla interface, type of support (tried them all), changing the print orientation, they all seem to not help at all. Looking for suggestions on that.

20250510_151726
20250510_1517261920×2560 467 KB

surface after struggling to remove any of the support
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20250510_1517381920×2560 570 KB

the top of the finished file
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20250510_1517441920×2560 615 KB

Before removing the supports

One of these photos is what the model is, one is

Also, for whatever reason, two of the parts are massively out of proportion, obviously I know HOW to scale parts, Im just not sure what to scale them to. The print notes say final height should be .359"/9.10mm but what does that mean? Which axis is height? Woudnt that change depending how its oriented?
Silver Files test.3mf (2.4 MB)
The parts in questions are on plates 1 and 4

Im sure im forgetting something…many things possibly

2

Scale is relative but if the height is the measurement you just pick a part and scale it evenly by entering the correct height for the x-axis.
The rest will scale to the same.
Works best to try first with just one or fitting parts, then reload the load to reset and select all models to scale them as before.
Can only assume the parts were placed correctly for this to work.

Print the support interface layers in PLA and use a 0.16 or 015mm z-top distance.
Set the pattern spacing to 0 to get a solid to surface on the support.
Still won’t look perfect but should come out in acceptable quality.

3

My next idea was to cut the model apart in studio so I could print both halves facing up then glue them together after. But because you can only make straight cuts the entire way through the model it seems like a pain in the butt.