My official, stained, dirty, greasy BMC Workshop Manual <span style="text-decoration: underline"> does not give a spec for this nut</span> (I'm not sure of the print date, but I got this manual when I was in high school),
My 1500 Midget manual (much newer) does not state a torque spec either.
It's funny that this is being discussed since I talked about this exact subject to Ralph Steinberg at the New Hampshire Vintage two weeks ago. Ralph has had a Brit-car repair shop in the Philly area for 35+ years. He's a super knowledgable guy about these cars. We were watching a guy pull a broken axle from an MGA racer (similar setup to Spridget) when I asked him what he torqued the hub nut on Spridget to? He told me, "usually, around a 100 ft. lbs or so".
It does say (on page "H.5" of my BMC manual) that you use 140 ft. lbs (or 19.4 kg.m.) to tighten the <span style="text-decoration: underline">pinion seal nut</span>
For reference, I'm using about 80 ft. lbs (and Lock Tite) on the rear hub nuts of my race car and so far, so good.
It's definitely a critical nut.
Racers call it the "J---s Nut" (since that's what you would say if it came off).
