How To correctly Align The Hole Needed When modifying An RB26 Timing Cover For VCT Clearance?

[God_Z_illa]

Hey everyone,

I was wondering what would be the most recommended methods used to properly align the location of the hole needed when modifying an RB26 timing cover to make clearance for the RB25 VCT cam gear?

It's a clear polycarbonate one from Nitto I bought naively years back as a cheap alternative to a factory 26 cover when I originally was planning to delete VCT for dual adjustable cam gears instead, but since then I've decided to retain it after doing my homework and realising how significant it's benefits are.

Since the material is delicate & I want to limit as much offset as possible for the hole to be clean and centered, I'm planning to consult my local plastic supplier that offer CNC milling of custom designs.

I appreciate any advice.

Cheers.

[robbo_rb180]

Measure from backing plate from the side and top and then from bottom timing cover to roughly find center. Cut with a hole saw slightly smaller them test fit and trim where needed.

I have cut a factory one and and used a few measurements off car to get it about right with a few mm of clearance and filed where needed.

[GTSBoy]

This ^. There are datum points on both the engine and the cover (ie, the mounting bolt holes) from which you can measure to find the centreline of the camshaft (on the engine) and just transfer that to the cover. It's a little harder because it's in 3 dimensions, but essentially the same as using a compass to draw two arcs from two centres to find the only common intersection point.

[God_Z_illa]

Sorry for my late response, thank yous both for the advice. Looking forward to getting a start on it.