BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: RichardAB on 11 September, 2017, 20:15:39

Title: B33 Exhaust valve guide
Post by: RichardAB on 11 September, 2017, 20:15:39
Hi
Please can anyone advise me the correct internal diameter of exhaust valve guide(cast iron) to suit 1960 B33. Plus tolerances
Thank you
Richard
Title: Re: B33 Exhaust valve guide
Post by: Bess on 12 September, 2017, 09:51:22
Hi,
    Exhaust

Guide part number 65-1516:

Length: 2 1/8" (53.9mm)
OD: 5/8"(15.9mm)
ID: 3/8" (9.45mm)

Valve part number 65-1240:

Head Diameter: 1 9/32" (40.6mm)
Length: 3 3/16" (97mm)
Stem Diameter: 3/8" (9.5mm)

Best wishes...
Title: Re: B33 Exhaust valve guide
Post by: chrisgoodwin on 12 September, 2017, 22:05:59
Hi Bess,
I am having problems with the exhaust valve on my B31 and shortly I want to get the head reamed and if necessary fit an over size guide
So the dimensions you have given are of great interest, but can I ask you to double check?
The outside diameter of a standard exhaust valve is 5/8" (15.875mm)?
But what is the diameter of the hole to accommodate the guide including tolerances?
Thanks in advance,
Chris
Title: Re: B33 Exhaust valve guide
Post by: Bess on 12 September, 2017, 22:33:17
Hi,
    The standard is 5/8", the mm dimension was rounded up. The oversize guide usually increases by +2 thou increments.

Cast iron or bronze guides in:

Cast iron cylinder head: 0.001" to 0.0015" interference fit.
Aluminium cylinder head: 0.0015" to 0.002" interference fit.

I have the guides professionally fitted, reamed after fitting and seats cut at the same time as its very unlikely the new valve guide and valve will match the existing seat line. I then lap them myself.

Best wishes...
Title: Re: B33 Exhaust valve guide
Post by: RichardAB on 12 September, 2017, 23:11:38
Thank you for info
Title: Re: B33 Exhaust valve guide
Post by: Bess on 13 September, 2017, 07:43:39
Hi,
     You're most welcome, I hope all goes well...

 :)