ETA 15D MK 3 AND ELITE - 5cc ENGINE BUILDS
Part eight - by Ramon Wilson
Part four - by Ramon Wilson

After milling the relief around three of the front housings....


....they were set up and the front bearing housing rough bored (this helps keep any stresses on the mandrel used later to finish turn them to a minimum).

Then the final milling op to mill the angles....
....before turning a close fitting expanding mandrel....
....to hold them for finish boring the front bearing housing.
The main/rear bearing housing registers on the larger diameter - a nice slide fit with no shake - and pushed back tight onto the face. The expanding part is just 0.01 down on 10.00mm. A very light nip of the screw is all it takes to hold it sufficiently to turn the .5mm left on the diameter and rear face of the front bearing housing. This op is one that has to be done with as much precision as can possibly be achieved as the bores for the bearings need to be truly concentric and in the same plane. Using this method provides the most consistent results to achieve this requirement with limited equipment available.

That 'protrusion' was finish milled and the induction hole drilled part way through to replicate the original. As the crankshaft is not going to be drilled to suit it was felt there was no need to drill all the way through and risk possible air leakage.

The corners were radiused by hand filing and all parts given a final going over with fine Scotchbrite type abrasive material and finally they are finished.


Though they may look a bit 'polished' these parts will all be bead blasted at some stage which will provide that nice uniform matt surface to even everything out.

Next time, the cylinder heads.


See part one here  part two  part three  part four  part five  part six  part seven  part eight 

part nine  part 10