Inner timing cover breather grub screw

[Superarnie]

Hi everyone.
I have recently had to replace my inner timing casing. On the old one, where the breather 'top hat' fits through the casing/cover, there is an internal drilling heading generally rearward (towards the gearbox) in which sits, what appears to be, a very tight flat head screw. The replacement inner timing case does not have that screw fitted and as such, when the engine is fired up, it just vents crankcase pressure out of this hole together with vaporised oil which subsequently drips down the surrounding components onto the floor. I have looked at my parts manual and can't find an image showing that grub screw. Can anyone advise if it's only a grub screw or if there is an associated washer as part of the assembly, and in either case, do you know the part numbers so I can buy replacements.
Many thanks
Gary

[muskrat]

G'day Gary.
Yes that hole has a blanking screw/plug so the crank pressure is sent to the other side of the motor.
I would just tap a thread and insert a grub screw with red loctite.
Cheers

[JulianS]

It is a tight fitting light alloy screw about 3/8 diameter. Maybe a slight taper on the short thread. Photos show one.

Not designed to be removed. This one from an A10 and was sealed with shellac or similar.

The whole of range 1949 parts list shows it as 67 138 for the long stroke A7 I suspect the same part fits post long stroke models. Not shown in the post 1949 books.

[Superarnie]

G'day Muscrat and JulianS,
Thank you both for your help and advice.
I found, when I removed the inner casing, that a 3/8 bolt is the correct diametre of that blanked breather hole. I tried a number of different threaded 3/8 bolts and one of them screwed in perfectly. It had a very vourse thread. I have very few thread guages but found a 16TPI Whitworth was very close if not exact. I then cut the bolt head off the shank and cut a slot in the end and with some red Loctite, screwed the grub screw into place.
Now, I have a follow on question, I understand that the breather vents through an internal gallery, parallel to the camshaft and across to the drivers side. I have read the it then vents through a hole on the drivers side near to where the camshaft blind bush is. I can't find this vent hole. Any ideas? I have attached an image of my drive side casing. Could someone see the vent hole?
Many thanks
Gary

[Superarnie]

Found it!!
For anyone who didn't know its on the underside of that rectangular (ish) bulge on the drivers side casing on my attached image.

Now, next question, compression gases and oil vapours will come billowing out of that small hole and drip oil down the casing onto the floor. I'm guessing people have tapped a connector into that hole and run a pipe aft?  Also is that a sufficient breather at higher RPM's, I read that some have put an address breather in the rear most rocker valve (Bunn valve? - obselete now?) cover. What is generally regarded to be the best breather modification today?
Regards
Gary

[muskrat]

G'day Gary.
In a perfect world (newish motor) there is little gases coming out that hole. A motor with sad rings will have more and bring oil droplets with it but the passage seems to cope.
The early models had a copper tube inserted and directed the gas/oil to the front sprocket.
A common mod is to fit a hose tail into the hole and run a hose to the rear of the bike.
On my A7 plunger I have no added breather mods and I thrash it with no ill affects. My highly modified A10 Cafe (ex A7SS race bike) I have plumbed it to the oil tank and vent the oil tank through a exit Bunn Breather, the inlet Bunn is piped to the exhaust rocker cover. I modified the top hat timed breather so it doesn't "time", the Bunn takes care of it.
It is a pity the Bunn is no more but I think there was a topic on other valves to do the job (may have been on a different forum).
Cheers

[berger]

i tapped the hole out 3/8ths whit and put in the brass piece that has a tube on it to blow the mist onto the sprocket , you can see it on the left hand engine.