What's the deal with these BB33 cases with the breather boss down there near the main bearing area??

Hi Douglas...All the cases have the boss cast into them...The breather itself was only located there for 46 and 47 on B31/33 motors...Ian

Of all my mates single cases I've never noticed?? I'll have a close look again at all his singles and take pictures.

Of course you're right Ian. Just never took any notice until I saw that blanking plug in this particular motor. Senility again. Anyway we took a chance on this engine on ebay and today started the disassembly and pleasantly surprised it has been sooped up with a high compression piston, cams,thicker through bolts, and what looks like a Matchy conrod with thicker bush to downsize to BSA gudgeon size.I've had Matchies all my life but never took much notice of the much beefier little ends on these rods compared to BSA singles.Obviously previous owner had racing aspirations!It also had a Bosch maggy attached.

Hi Douglas..Yes, the Matchless con rod is a fairly common alteration for the B31/33 motors to provide an economical rod upgrade....

Strictly speaking the later crankcases are a better proposition for a very tuned motor that is used for racing, with wider 'webs' around the periphery and the additional strengthening around the drive side bearings and tappet chest...

For fast road use though, any of them will work well I have found..

Sounds like you did OK with your purchase!...Ian

Another mystery for me? These pushrod tunnels? Never seen the skinny one before.

Too many jobs to do!!

Hi Douglas...The pushrod tube on the right is the pre 48 style, with the smaller piled arms logo and the more rounded profile.

These were either a die casting or were made of a poor aluminium mix (I think the former) as they are usually pretty much impossible to weld if required....

Nice chair...and yes, you do have too many projects... ...I know the feeling...

I can tell that workshop isn't in blighty...with a non insulated roof like that and our climate you'd be wading about in an 1" of water and everything would be dripping with condensation.. ....Ian

email (option): ian@wright52.plus.com

Strange, I would have thought the skinny one was earlier as we have plenty of the more rounded ones?

Hi Douglas...The 'skinny' one is the 48 and later type and would be used with a timing cover with the 'winged' BSA logo...

The more rounded type are used with the earlier timing covers which had the smaller, 'wingless' BSA logo (as used on WD engines)...

The later type are also sand cast...Ian

email (option): ian@wright52.plus.com

I'll put that in my Funk and Wagnall Ian!