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B cylinder oil hole vs C cylinder oil hole

craig

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VOC Member
I am fitting new liners in old C barrels (muffs) for a 6xxx Shadow and decided to study the oil hole placement. I have a B series apart as well and the oil hole placement is much different. I go back and read KTB, Richardson, and other references...........and I find myself unhappy that there is not a dimensional sheet to study to establish ring position vs oil hole...............and a 50 degree axis reference for the 3/32 hole for later cylinders.....and a "groove" referenced which is so wide as to go beyond "groove" as I call it.
Also 1" x 3/32" wide woodruff key seat cutter, use of it not making any sense to me, as the flat cut is 1/2 wide.
There is no reference as to where to clock position this hole, there is no reference as to checking the cases to allow for your best hole position.
I would like some help with a dimensional drawing showing ring vs oil hole.
Should all the early Bs convert to later liners with lower oil holes due to excessive B oiling?
What is the 50 deg hole advice?
Thanks, Craig
20140610_BCOilHoleCompare2.jpg
 

craig

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VOC Member
Here is a print portion from one of the manuals with piston moved, by me , to BDC. But I am not sure it is down far enough.
EngineBDC.jpg
 

timetraveller

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VOC Member
Craig, I am not sure that I understand the problem. The 'C' barrel you show has had the 'groove' cut too wide. There is no need for more than a slot or groove about 3/32 wide. As for how far down it should extend then if you have access to the engine with the barrel removed just measure the distance from the top of the opening in the crankcase to where the oil hole comes out of the back of the spindle. Whether it is a 'B' or a 'C' the same applies. All you are trying to do is to ensure that the oil coming out of the back of the spindle can get to hole through the back of the liner. It should be fairly obvious what you are trying to achieve which is why I wonder whether I have understood your query correctly. Just to put your mind to rest some of the best Vincent racers do not use the oil hole in the back of the liner at all so it is probably not critical.
 

greg brillus

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VOC Member
It really comes down to what pistons you are using and their piston ring placement.....that part of the equasion is most important if you are to have oil going to the skirt only and not between the rings as so many are. Fit the piston without the rings, and measure as accurately as you can before drilling any holes.
 

nkt267

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VOC Member
I'll see if I can take a photo of my spare barrell to show what I did..john
 

craig

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VOC Member
Thanks to all for advice, I am having trouble picturing the following words from tech sheets
Modified Oil Hole
On 1951 and subsequent units the 3/32 inch oil hole is drilled at an angle of 50 degrees to the axis of the barrel, feeding into the outside of the liner with a 1 inch x 3/32 wide Woodruff seat cutter 7/8 inch below the face of the jacket. This groove ensures that the hole, thus positioned lower to feed below the scraper ring, will communicate with the gallery in the crankcase mouth.

I measured all I have, and it is clear a B Rapide oil hole, round one pictured above, puts oil between second ring a scraper (oil ring).
The C cylinder barely puts the oil below the oil ring.
It does not matter what piston you have, as the oil ring is always put in a fixed position with the wrist pin for a Vincent, other wise you would be solving oil hole problems with every piston.
both my B cyl and C cyl put oil in at 90 degrees...........what is this 50 deg?
Any pictures of such ?
Craig
 

nkt267

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VOC Member
I have tried to upload photo's of an original barrell for a C,but everything i try does not work 'file too large'...john
 

nkt267

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VOC Member
The first image is of a modern replacement liner that I fitted.I found it easier to machine the slot with an end mill than use a Woodruff cutter.Note that the liner is waisted a lot higher than the original liners and the liner/crankcase fit is looser.
The 2 photos with the muff on are I believe and original barrell/muff off of a C..hope this helps ..john
 

Oldhaven

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VOC Member
As Timetraveler mentions in his "not to worry" above, my B Rapide rebuild will have the cylinder oil feed blocked off and will not use the cylinder oil holes at all, though they are there and could be used if necessary. This was recommended by the long time racer/mechanic doing the rebuild. (He knows how to get the piston clearances right.) This is engine 1154 and uses two piece cylinder bolts. The outers are not waisted like the later one piece bolts and there is a less sealable arrangement between inner and outer bolts than the cylinder oil feed gallery groove in the crankcase thread of the one piece bolts. He was worried about oil creep up the two piece bolts causing a leak. I am sure this has been covered thoroughly in MPH somewhere in the past, but have not found the right search words to verify this. I am not sure if any difference in the hole position and slot shape shown above has to do with this difference in types of cylinder/head bolts for earlier B's, as I can't see that that matters. I note that Richardson mentions that the holes were moved lower in 1951 to come in below the rings.

Ron
 
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