ET: Engine (Twin) Series ‘D’ Breather

Bill Cannon

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Can anyone tell me if the series D timing spindle blocks off the breather hole into the crankcase.
I am thinking of moving my breather from the valve cap to the series C breather outlet so I have a vertical path for the breather pipe.
The outlet on mine is blanked off by a 3/16th BSW bolt, how much can I open this out to fit a stub for a breather hose?
Cheers Bill
 

timetraveller

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I have the prototype Black Knight so it is not typical. The hole on that is machined but blocked off. My memory is that in general these holes are not even machined. Instead the casting is left as original and a small bolt fitted which is used to secure the distributor cover.
 

mercurycrest

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There's no breather hole on my D. That's where the Distributor Cover screws down (see MO32). You'll need to plug up the C breather hole, or the D breather won't work.
 

Cyborg

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Can anyone answer this please and thank you....There is a flat on the D breather spindle. What purpose does it serve and does it have to be indexed?
 

timetraveller

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I'm not sure what you mean by the D breather spindle. The D breather is the vented valve spring cap. The original breather made use of a hollow and slotted spindle for timing the breather on the Bs and Cs. The spindle in the same place on the Ds should be just a plain cylindrical shaft to carry the idler to drive the distributor pinion. A flat cannot serve any useful purpose and might reduce the bearing surface for the pinion and its tubular centre piece. There would be no good reason not to use a B or C breather pinion assembly as a substitute for the D item but the slot in that would serve no useful purpose.
 

Bill Thomas

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Don't think it matters where the flat goes, But it might help with the lubrication ?.
There is something funny with the Twin Vincent breather pinion setup, Because it needs more end play than the other spindles, The tube part has been known to break off where it goes into the pinion.
It helped in "Stuffing" my Special 2 years ago, When the fibre pinion sheared, I found the breather pinion was spinning on the tube part, After not being touched for 38 years !.
 

BigEd

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I had a problem with the breather pinion seizing. It has a dural bush. I gave it a bit more diameter clearance and a bit more end float. Seems OK now.
 
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