I'm just about to fit the engine to my G12 and am making up the various studs required.
I'm a bit confused by these two however that are tapped 3/8"BSW on the drive side, there is a 5/16" dia hole that goes all the way through.
Can anyone tell me what they are for?
Unfortunately, I can't seem to be able to attach the pics. One hole is below the oil filter and the other below the inlet cam.
TIA
Engine fixings
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Columbo John
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Groily
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Re: Engine fixings
Looking at a pic of a bare 1961 G12 drive side case there are 10 holes in it (plus the support on the cast web for the primary chaincase, the oil filter cap, camshaft end plugs and the three tapped holes for inner primary case retention).
Two of the holes are for 3/8th studs, the rest are for 5/16th crankcase bolts or for 5/16th through-studs for engine plates. The two bigger ones are at 3 o'clock and 7 o'clock if you look at the case straight on.
Dunno if the earlier motors were the same, if yours is earlier, but the above is what I have here if it helps.
Two of the holes are for 3/8th studs, the rest are for 5/16th crankcase bolts or for 5/16th through-studs for engine plates. The two bigger ones are at 3 o'clock and 7 o'clock if you look at the case straight on.
Dunno if the earlier motors were the same, if yours is earlier, but the above is what I have here if it helps.
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Columbo John
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Re: Engine fixings
Thanks, mine is a '61 as well. I' m not in front of the engine right now but it certainly sounds the same. I'm just confused about the two tapped holes.
If I could figure out how to upload a pic, you'd see what I mean quite clearly.
If I could figure out how to upload a pic, you'd see what I mean quite clearly.
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Groily
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Re: Engine fixings
Me too (confused that is!)
Could it just be that impressions of the threads have been left on the alloy by virtue of their being a tight fit and having to be 'wound in' a bit when the engine was last fitted? I've seen that before now on some engines . . .
Pic would be good if you get there.
Could it just be that impressions of the threads have been left on the alloy by virtue of their being a tight fit and having to be 'wound in' a bit when the engine was last fitted? I've seen that before now on some engines . . .
Pic would be good if you get there.
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SPRIDDLER
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Re: Engine fixings
My post in the following link may help...........Columbo John wrote: ↑Mon Jan 31, 2022 9:39 am
If I could figure out how to upload a pic, you'd see what I mean quite clearly.
viewtopic.php?f=19&t=27956&p=237049#p237049
'There is a tide in the affairs of men
Which taken at the flood............'
Which taken at the flood............'
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Columbo John
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Re: Engine fixings
That's great thanks 
Here are the pics that clearing show the 2 tapped holes.
Here are the pics that clearing show the 2 tapped holes.
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Groily
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Re: Engine fixings
See what you mean. Very clearly.
I've just blown up a hi res pic of a drive side case I have here (too big to attach as a file) but those 2 holes on mine also have 'threads', rather vestigial on the one below the oil filter tunnel, deeper on the other one at the rear. Yours are both more pronounced than mine.
I then looked closely at a spare engine, a 500, to see what that was like - and lo and behold, a vestigial thread in the hole under the tunnel, and more pronounced on the one at the rear. A 3/8th BSF bolt would go in just a turn or so - but the majority of the depth of the holes is 5/16th like you say and no sign of any 'thread' other than towards the drive side ends.
Just the same on another spare set of cases lying around the place, which also has 'thread' on the same two holes, and on the lowermost one at 6 o'clock as well.
Weird, but they are just 'holes'. Quite how they have ended up looking almost like they have a proper thread I don't know - can only think it's because fasteners have been wound in against the weight of a loosely attached engine, maybe very slightly bent ones even, and have done it. But if so, they've done it quite neatly in your case, a bit roughly in mine!
Or - edit - maybe someone thought they should be there having seen the tell-tales, and ran a tap in??? Stranger things have happened I guess!
I've just blown up a hi res pic of a drive side case I have here (too big to attach as a file) but those 2 holes on mine also have 'threads', rather vestigial on the one below the oil filter tunnel, deeper on the other one at the rear. Yours are both more pronounced than mine.
I then looked closely at a spare engine, a 500, to see what that was like - and lo and behold, a vestigial thread in the hole under the tunnel, and more pronounced on the one at the rear. A 3/8th BSF bolt would go in just a turn or so - but the majority of the depth of the holes is 5/16th like you say and no sign of any 'thread' other than towards the drive side ends.
Just the same on another spare set of cases lying around the place, which also has 'thread' on the same two holes, and on the lowermost one at 6 o'clock as well.
Weird, but they are just 'holes'. Quite how they have ended up looking almost like they have a proper thread I don't know - can only think it's because fasteners have been wound in against the weight of a loosely attached engine, maybe very slightly bent ones even, and have done it. But if so, they've done it quite neatly in your case, a bit roughly in mine!
Or - edit - maybe someone thought they should be there having seen the tell-tales, and ran a tap in??? Stranger things have happened I guess!
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griffin
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Re: Engine fixings
The 2 tapped holes were they used to bolt the case to a fixture during machining ??
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ajsph
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Re: Engine fixings
there is 3 holes with 3/8 BSF thread, the 3 holes are very practical, see picture
Poul
Poul
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Groily
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Re: Engine fixings
Now I'm upset Poul - as I only have the remains of threads on the two holes, same as Colombo John! Woe, woe . . . .!
Only got one other engine (a 500 which I don't have a pic of disassembled) but I'll look at that next time it's out to see if it has the third thread (or remnants of it) down at the bottom. My Mod 31 has nothing down there though, it's a smoothie - or has been taken out by a PO.
I will clean up all my 'vestigials' with a tap if they will, so they are ready to assist with bottom end assembly like in your very excellent picture. (I have usually used a bench with an 'ole in it for the drive side mainshaft when putting them together - should have sussed the 'better way' about half a century ago!)
Only got one other engine (a 500 which I don't have a pic of disassembled) but I'll look at that next time it's out to see if it has the third thread (or remnants of it) down at the bottom. My Mod 31 has nothing down there though, it's a smoothie - or has been taken out by a PO.
I will clean up all my 'vestigials' with a tap if they will, so they are ready to assist with bottom end assembly like in your very excellent picture. (I have usually used a bench with an 'ole in it for the drive side mainshaft when putting them together - should have sussed the 'better way' about half a century ago!)