General
A Overhead Camshaft engine is an internal combustion engine with the camshaft placed in the cylinder head.
The NSU Ultramax camshaft drive operates with 2 push rods, which rotate on eccentric disks.
Details you can find here:
NSU Ultramax Camshaft Drive by Bootjevaarder - MakerWorld

This model has a total engine capacity of 60 cc.
Choise between an open and closed design of the cylinder head.
Dimensions: 185 x 103 x 173 mm.
Weight: 0.36 kg.

Printing and Assembly
I printed the model on a PRUSA Mini, with PLA+ filament, layer height 0.2 mm.
The parts should be printed on a smooth build plate, not textured.
If possible, avoid elephant foot.
I use Hard Plastic Glue where necessary.

For 3D views, use .stl files 00… 01... 02… 03… 04… 05… .
Printing and assembly in alphabetical order, A1 → J1.
Instructions for printing and assembly is available for many .stl files.


Post-processing
As always with mechanical models, be sure all moving parts run smoothly.
I use files, sandpaper and sharp hobby knifes. A few drops of motor oil may help too.
Pay special attention to seams on bearings and axles.
Maybe you need a 5 mm drill to widen the four valve guides in the cylinder head.

Metal parts
Eight M4 x 25 mm allen bolts are needed to join the cylinder heads to the cylinders.
Eight coil springs are needed as valve springs, 10 mm width x 15 mm height. Wire thickness 0.6 or 0.7 mm (AliExpress).


Valve timing
Initial valve timing can be executed when glueing "G1 - Base Plate Ultramax" to the cylinder.