There are two washers on each joint - one under the head of the bolt and the other between the oil feed and the face of the block/head. If both washers are the same thickness the hole in the bolt will remain central to the hole in the oil feed - so where is the possibility of misalignment and restricted flow?
Frankie
Try it out. It’s a matter of the thickness of the washer under the bolt head.
Doh! Another senior moment. 
Update:
I’ve taken the pipe off, and given the suspected area a good rub down. No sign of a split that I could tell, but I put a layer of solder over the area anyway. I also bought some new copper washers - just plain flat ones, about 1mm thick. The ones that were on there were the very thin ones with a curled over ‘lip’ and to my eye they didn’t really look up to the job.
Anyway, I’ve run the engine up to temperature, and there is absolutely no trace of oil. Next test will be a decent road run but with the current weather here in the UK (snow) it ill have to wait a few days.
Tim, if the problem returns dont overlook what John said above. It is very important to anneal the Cu washers even if they are New. You will not have to crank down on them to get them to seal as Erica noted above. Cheers Jim
The proper copper washers are very thin; thinner than a playing card. Much thinner than the copper washers used for the chrome nuts on the cam covers for example.
I’d use the correct washers , and if concerned about a leak I’d smear a bit of sealant on each side of each washer before installing them.
Tim,
I’m really nervous about using thicker washers here - particularly the one adjacent to the banjo bolt head. As a;ready mentioned, if you use a thicker washer, the oil hole in the banjo bolt may be partly or fully covered, and as a result oil flow to the head significantly reduced. Before rejoicing about the “no trace of oil” I’d be looking in through the oil filler cap to make sure that there is plenty of oil flowing in the cam area.
-David
What is people’s experience with the braided replacement lines like this?
Seems like a good upgrade but I believe I’ve seen some comments about reduced oil flow. Curious if anyone that uses these lines can comment. My Mk2 lines are not leaking yet (engine was just rebuilt and is currently out of the car) but it’s original and has a pretty good nick in it…so I’ll replace it before putting the engine back in the car.
Tom
I may be wrong on this but…the oil hole in the bolt will not necessarily align with the end of the oil feed pipe (depending on what rotational position the bolt is in when fully tightened) and to overcome this the fitting at the end of the pipe is slightly hollowed out so that oil will flow through. It therefore seems that it is not essential for the two holes to align for the flow to be sufficient. Presumably therefore for the flow to be restricted by using a thicker washer, its thickness must be sufficient that the hole in the bolt is partially covered by the edge of the fitting. Would not his condition be visible on assembly?
Frankie
It doesn’t matter if the hole in the bolt lines up with the feed line. There is an annular space (if that’s the correct term) that runs 360 degrees around the fitting. Oil flows up the line into that annular space, through the holes near the bolt head and down the hollow center of the bolt. The fear is that a thicker washer near the head would displace the bolt holes to the extent they are partially blocked by the edge of the fitting.
Mine leaks on lhs. Changed the copper washers the thin style, still leaks grrr. Might be the brazing. I’ll take the pipe out , but A/C hoses are in the way to get to bottom banjo. How did you manage that?
So it should be possible to settle the point one way or the other by measurement and calculation, thus identifying the max thickness of washer possible before partial obstruction occurs. Has anyone done this? If not, I will take one of my oil feed banjos off tomorrow and let you know what I find.
Frankie
That would help - thank you! Unfortunately, with all the aftermarket stuff about (reproduction pipe sets, both original style and braided, and banjo bolts both original and extra length), any measurement will be only one data point, but still a good starting point.
-David
Umm. At the risk of sound like the other word for donkey hole. In order to anneal, the glowing orangish part is correct but then let cool without quenching in water, This will bring the metal back to it’s natural state of hardness.
Mark,
Are you sure? As I understand it (it comes up frequently on this forum), copper can be quenched in water or allowed to cool in air when annealing. Copper, Silver or Brass can be quenched in water. Ferrous metals such as steel must not be quenched in water but allowed to cool slowly. The advantage of quenching copper in water is that it tends to cause the surface oxides to flake off, which doesn’t happen with air cooling.
-David
I guess you’re right about copper brass bronze silver (nonferrous) metals can be quenched, and the oxides do pretty much come off. I was welding (not soldering) I was messing around with my TIG welder and wanted to see if I could TIG Weld copper. I could weld Copper using solid copper house wire as the filler. I quenched it and it was really soft, and brittle it cracked at the first bend. When I let the metal cool down naturally, The copper didn’t bend the first time. Still really soft. I ended up brazing with Silicon bronze. So it would be stronger.
For whatever that was worth
I think we are in danger of ‘over-thinking’ these washers! My observations:
Firstly, the washers I took off (the ones with the folded over ‘lip’) are not original to the car. They were fitted when I had the engine rebuilt in the 90’s. I suspect, though am not an expert, that the originals were plain, flat washers.
Secondly, I have measured the thickness of the washers I took off, and they are approximately 0.9mm. The new washers are approximately 1.1mm, only marginally thicker. Since the hole in the banjo bolt is some 2 or 3 mm, I can’t believe there is any danger of blockage by misalignment.
Thirdly, and I think most significantly, I also measured the width of the washers (i.e. the flat surface that actually mates with the head of the banjo bolt and the face of the cylinder head). The washers with the lip are only about 1mm wide, compared with 2mm for the standard flat washer. In other words, the standard flat washer has a much larger surface area. Surely this has to be better for making an oil-tight seal?
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
Thank you Frankie for taking to time to take the measurements, and then publish your findings. They confirm what has been stated on this forum for some time - using anything other than a very thin copper washer between the banjo bolt head and the banjo fitting will significantly restrict the oil flow to the head. Your comment about the distortion of the rubber part of the stat-o-seal causing further restriction was also noted by Jerry Mouton in the past - I think in the context of trying the braided pipe replacement. It’s possible that the aftermarket banjo bolts have been designed to be used with a thicker washer, by having the oil feed holes drilled further from the base of the hex head, but I’ve not seen any measurements to suggest this. Either way, it seems that it would be wise for anyone contemplating replacing any of these components to make sure that the set they use (banjo bolt, banjo fitting, sealing washer) are mutually compatible so that the oil feed holes in the banjo bolt align properly with the channel inside the banjo fitting.
-David
I went with the braided flex line and washers with the rubber grommet, the leaks are gone forever AND it looks really good!
Get ready for my new book ME AND MY ETYPE! Adventures over 30 years!
GTJOEY1314