I removed my oil feed and all three banjo bolts complete this morning and took some measurements. The engine is a 1971 4.2 L unit in a Daimler Sovereign. The banjo bolts and oil feed pipe appear to be original. The part number for the bolts is C5846 and all three are the same. All measurements given are as near as I could measure with a digital micrometer.
There are two holes in the bolt shank; each is 2.7mm diameter
The internal diameter of the oil feed pipe is 2.7mm – 3.0mm (difficult to measure accurately)
The “lip” of the fitting at the end of the feed pipe is 3.2mm wide (varies slightly)
The distance from the underside of the bolt head to the nearest edge of the oil hole in the bolt is 3.0mm (excluding the splay at the hole edge)
The thickness of the Stat o Seal washer supplied by SNGB is 1.3mm.
It will be apparent that there is no significant allowance for the thickness of a washer under the bolt head but some comfort that there are TWO holes in each bolt, fed by a single pipe of approximately the same internal diameter. The thickness of the Stat-o-Seal washer at 1.3mm does restrict (significantly in my view) oil flow (3.0mm – 3.2mm – 1.3mm = -1.5mm).
More worryingly, when I removed the Sat – o - Seal washers, I found that the neoprene ring had distorted and squeezed into the annulus of the fitting in three of the six washers fitted, further restricting flow.
I would welcome a second opinion/review using another engine, but I for one will not be running mine again until I fit the proper copper washers.
Frankie