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E: Engine How critical are the rear cylinder oil feeds!


Marcus Bowden

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VOC Member
Never used a torque wrench on a Vincent or re-tightened (re-torqued) heads down again, right length of ring spanner and reasonable strength .but always used the same spanner.
bananaman
 

vibrac

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I needed to reread this thread as I have a special engine where the oil hole in the crankcase side will never feed the piston correctly I note that while the term 'blocking off' occurs a number of times nobody has specified the best way to do it my barrels have not had the oil hole drilled is that sufficient? I would rather have the oil on the cam than perhaps funneling back to the crankcase in the annular gap twixt cylinder and case
 

greg brillus

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The simplest method I have seen is to cut some thin discs from either shim brass or steel say 10 to 15 thou in thickness and sandwich them behind the ET 183 seal in the timing cover.
 

vibrac

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I must be wrong:oops: I thought the feed up that spindle also lubricated the camshaft bushes etc as well as the cylinder bore hole
 

Bill Thomas

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It must make a bit more pressure to the cams etc by blocking the follower spindle.
Not sure I can bring myself to do it, But it might be more easy, That hole never seems to line up !, At the right place below the rings. Cheers Bill.
 

davidd

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VOC Member
Oil Diagram.jpg
This is for the twin. The only item that may be hard to picture is the "recess". That is the chamber in the back of the cases where the oil goes after it is scraped off the flywheels.

The Comet is a little different. Only two oil feeds on the Comet. One to the camshaft and the cylinder wall is fed by the intake cam follower spindle.

I think Greg's method with a shim is probably the best. There is nothing that can come adrift to circulate in the oil system. Presumably, any additional oil running above the jet would be available to go to the cam. It is difficult to know how much that would be. The supply seems more abundant, but it is flowing through the same size hole.

David
 

Marcus Bowden

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Same cams for over 300k miles fitted 1970 Mk2's originals with holes in leading face of cam (thanks to Pete Green) first 100k wear was evedent 0.006" to 0.012" most wear noted on exhaust cams (opening against greater pressure) first pump fitted by the originator Herve" Hamon in 1990 whilst sleeving main bearing housings .Since p/p fitted less than a 0.001" on roughly the same time period.
When fitting the Honda P/P the first thing was to fit a wear to the suction of main P/P. this allows the oil level in the cavity behind flywheels to build up BUT not so high that it is higher than the cavity wall.
The tube can be seen with a hole very near the top and suction line secured to outside wall of c/case and set back into into the aluminum of the c/case as flywheel very close, set suction end to 1/4 of diameter of bore to the bottom of C/case for optimum flow.

P1050264.jpg

BETTER OVER VIEW

P1050263.jpg

INTO TIMING CHEST THEN A BLACK PLASTIC PIPE IS USED AND THREADED THROUGH THE TO LEFT HAND SIDE OF THE IDLER BOSS BRACKET PIPE HOLDER.
P1050265.jpg
 

vibrac

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Well then it would seem to me that lacking an actual hole in the cylinders the best course would be to just leave all as is. Some oil would get down to the crankcase but I guess the supply to the cams would be better
certainly with the changes on this big bore twin the hole could never be in the right place
 

greg brillus

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Big bore engines say with the TP top end kits, I extend the oiling groove around the rear of each crankcase mouth with a dremel and small rotary burr to the center as per original, then double check the piston ring to bore/liner heights and drill the feed holes through each liner, then run a small vertical channel up to meet the groove in the case mouth. Lets not forget that the biggest restriction in feed to the cams and cylinder feeds is the 170 jet in the timing chest. There is nothing stopping you opening that up larger or remove it completely. With the racer that's what I did, but kept the jet holder in there, this in itself is enough of a restriction via the two holes on either side which allow plenty of oil flow. There are mods you can do to allow better feed to the cam lobes and follower surfaces without going to too much trouble.
 

Oldhaven

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My Rapide has undrilled/blank restrictor disks in the cylinder feeds. It is a '48 with 2 piece cylinder studs so oil taking the usual route to the liner hole is injected into an area where the ET158's in early machines are seated. The installation/removal castellations in them below the outers can allow oil to get into the space between the inner and outer stud and travel up the stud to the top of the head. Not a problem with later one piece studs fitted with sealant. This means more oil to the cams I guess.

I had not known that it was an option to not use the .170 jet in the jet holder, or to use a bigger one, and I remember some discussion years ago about how that might decrease the oil going to the big end, and maybe the top end and rockers. I imagine for a twin that might be the case, but for a single with half the bleed off and demand it might make some sense. I'd like to hear more on this.

My big bore Comet project will also have a blank disk in the cylinder feed and no liner drilling, partly due to the bad location of the incoming gallery, (which, as Greg mentions, can be remedied), but mostly because I can't see sending oil off into unused areas for no reason.
 
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greg brillus

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Hi there Ron, Not so much that it is an option to either use or not use the Jet or its holder, more so for a racing engine. The jet or "Restrictor assembly" is there obviously to keep some oil flow/pressure to the crankshaft. It is well known that a roller bearing crank does not need much lubrication to work well, and high pressure to a roller crank will cause it to fail as the pressure will "Lock up" the rollers causing them to skid across the tracks. Given most race Vincent engines run a two start pump, the oil delivery is better, so you can afford to open up the passage to supply the cams a bit more. A lot of racers run the standard pump and this too can work fine, it all comes down to what works for any individual engine. From my limited experience with racing Vincent engines, it is the cams/followers that are the weak link, but I strongly believe it is the choice of components and how well they have been made/hardened that affects this.
 
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vibrac

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VOC Member
Had a final check on the oil feed position at BDC the oil hole slot in the barrel will need a 12mm move towards the drive side and a drop of at least 5mm to exit below the oil ring and keep in the crankcase/bore coverage area (Excuse for foreign measurements its a stroke and bore area:oops:) however at TDC and for a considerable crank rotation it will be squirting into the abyss as the skirt wings its way upwards
I think I shall block the supply as suggested.
 

erik

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if someone is not shure to block or not to block the oilfeed to the cylinders ,i think only blocking the rear is an other idea .because the flywheels throw the most oil towards the rear cylinder not the front one. Erik
 

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