B31 EXHAUST VALVE

[EDDIE SIMPSON]

hi b31 experts. i will need to buy a reamer for the exhaust valve guide. my valve stem measures 0.350" just short of 9mm. but what size reamer do i need to buy? 9mm may be too big?

[Gadorey]

How about buying an adjustable reamer?  Then you can ream to the exact specified tolerance between valve stem and guide.

[Pete C]

I use these adjustable valve guide reamers


https://hirschland.de/Hunger-Ventilfuehrungsreibahle-Typ-V-84-9
this one is 8.4-9mm,
and a Flex-Hone to finish.

it's not cheap if you are only doing one!

[EDDIE SIMPSON]

o k  thanks for replies and an adjustable 6/9mm reamer added to santas list.

[Calum]

If it's something you won't use often don't spend a fortune. RDG Tools are just down the road from my house and do a great range of tools aimed more at the home engineer/model making etc market. They have a great range of stuff at sensible prices, and the quality isn't bad at all. They seem to have a selection of adjustable reamers. One with HSS blades is only around £12 inc VAT.

https://www.rdgtools.co.uk/acatalog/REAMERS.html

[Pete C]

just for reference
exhaust valve stem 0.348 inch, guide bore 0.352-0.353 (8.94 – 8.97mm) so 9mm is too big.
If you live in the US you can quite easily find reamers of all sizes in inches, but it is not so easy here 

[Gadorey]

One important point - the only important figure you need to keep in mind is the clearance given in the manual between valve stem and guide bore.

I don't know if you are using your old valves, but if you are, the the stem has probably worn off some. If you now ream the guides to the factory specs, then the clearance will be too large and not work as it should. So measure your stems, add the clearance given in your manual and this is the bore size you want to aim for with your reamer.

[EDDIE SIMPSON]

very lucky result. amongst all my metric reamers i found one with no markings but measured 8.86mm and the new valve fitted perfectly. i agree 9mm would have ruined the interference fit. its probably a machine shop 9mm interference fit reamer.
i dont mind lending the reamer out to any b31 owners on this site for exhaust valve fit only.