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E: Engine Bid End Rebuild


litnman

Well Known and Active Website User
VOC Member
I'm looking at a new big end pin here with the oil passage not connecting with the oil passage in the flywheel. All timing side flywheels I have
are the same as the one shown. All old pins I have are relieved in the shoulder of the pin to allow oil from the flywheel into the pin.
Not sure which way to go here, grind a groove in the pin or a groove in the flywheel, which may cause the pin to eventually lose some tension.25913
 

greg brillus

Well Known and Active Website User
VOC Member
The pin is harder than the flywheel material so i would grind a small slot in the pin, given this is the serviceable part over the flywheel. Make sure the pin has enough interference in the flywheel and the nuts need to be done up very tight.
 

litnman

Well Known and Active Website User
VOC Member
I agree with you Greg. Have you seen this style of passage hole before?
The new pin is a 1-1/16" and will get a .004 fit.
 

mercurycrest

Well Known and Active Website User
VOC Member
Hi Jon,
Who made that pin? I've never seen one like it, but then, I haven't done one in 15+ years.
 
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Vincent Brake

Well Known and Active Website User
VOC Member
I agree with you Greg. Have you seen this style of passage hole before?
The new pin is a 1-1/16" and will get a .004 fit.
thats a hudge 0,10mm, like a fit for a temperd steel flywheel i gues?
normaly in mild steel i do the diameter divided by 600 max 500 for if tighter the bore will get damaged and leaves you with no fit at all, or?
maybe you use cold and heat?
could you let me know, as i am at the same work now...
 

oexing

Well Known and Active Website User
VOC Member
Litnman, why not try to revert to the old hole position in the flywheel ? Start with a dremel burr and drill at an angle into the present oil way in the flywheel. Finally plug the wrong exit with an alu plug. The side oiling design does not look to supply an even distribution for both conrods.
Press fit for pressed up cranks i do with 1/360 of in diameter as recommended by BMW on their classic post war twins, means 0,10 mm for a 36mm crank pin. But that is a very strong fit requiring an hydraulic press and on Vincents this was not the case so maybe only half of this percentage is standard. Very important to polish any radii on the pin so not to f*** up the flywheel bore.
Vic
 
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litnman

Well Known and Active Website User
VOC Member
Monday I will contact Coventry Spares for the pin Mfg. Has anyone else seen a pin
finished out this way, or a stock flywheel that would accept this type of pin.
 

Cyborg

Well Known and Active Website User
VOC Member
I haven't seen that many Vincent pins in my life, but none were like that. Norton Manx and Inter pins are drilled like that and presumably their other singles as well.
 

litnman

Well Known and Active Website User
VOC Member
It is a Maughn pin and John Healy suggest drilling a passage from the center of the bore in the flywheel to intersect with the existing hole. Turned out ok.
 

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