Bolt, fixing rear end cap, oil pump, 5/16 in. by 3.BA thread

[56G80S]

Hi Mick

That's a big help, thanks. I will do as you suggest. I might get nuts and bolts/set screws and test the screw in nuts rather than the case itself. I do have a set of old BA taps and dies but would prefer to go the route using the nuts.

Johnny B

[56G80S]

Forgot about the large number of small diameter bolts and nuts Dad left me. Found two straight away which threaded nicely onto the "unknown" set screw. A 2BA tap in my fingers fitted the nut perfectly. So it looks like it's a 2BA set screw and I have some on order.

Thanks for all your interest and help. I have to say that it's the pleasure of being a member.

By the way, although the correct thread, the set screw was clearly well used and and a tad sloppy in the nut. The new set screws may in themselves improve the position.

Best wishes

Johnny B

[REW]

Johnny, I am sure you will test the fit of the new screw with a 2 BA nut and then the actual fit in the hole. If it is still a tad loose I would use a turn of PTFE tape to take up the slack and also prevent the new screw unwinding. This I have done in numerous similar situations over the years.

[uas526]

What about filling the hole with metal putty and retapping to original size? That stuff sets rock hard. That bolt doesn't take a lot of strain/weight. The putty should be hidden by the end plate. Ideally it should be welded up and retapped, but that's skilled work.

[56G80S]

Ron, cheers

Dad to the rescue. In his box of small fasteners there was a 2BA screw that looked unused. It bottomed out just a turn or so from the underside of the head meeting the crankcase. It was nice and firm. Care measuring before cutting the new set screw so I get full engagement but still a pinch on the end cap and the stud idea can be forgotten. I reckon there'll be a third more thread in play than with the old screw.

PTFE may be better than the threadlock I planned to use but tricky to get onto such a small diameter. Nonetheless, it would support the first part of the thread in the crankcase, where it is weakest. They only need nipping, after all.

Just need to get the blanking screw by the sump plug out now. The ones by the pump were tight but this one's a swine and I want to make sure all the oilways are clear.

Johnny B

EDIT - uas526 - Thanks for the fill, drill and re-tap suggestion. You'll see from the above that I think an oversize set screw will do the job. Drilling and tapping in that area is hard so I'm pleased it won't be necessary

[56G80S]

I've been researching threads and realised I hadn't had the decency to round off this "thread"! Thanks for all the observations.

I went with my plane and it's made a good job, the 2 BA stud is very secure and I have to be honest, with hindsight I wish I had made all of these studs, the 3 BA included, however, Ken de Groome not only freed off the new drive side mains and line reamed the timing side bush but also re-assembled in the crankcases fully sealed.

So I'll leave well alone and just go steady when nipping up the rear end cap. IKBA, but studs into aluminium seems a better idea.

JohnnyB