I agree with John, the telltale just acts like a piston, the close fit in the bore is the only 'seal'. Looking at John's photo you can see that the rocker feed hole is indeed open all the time so as I said before the key is to make sure there's enough back pressure at the rocker feed/gauge to push out the telltale and open the big end feed hot or cold.
While the cover is off it's worth measuring how far out the telltale needs to come to fully open the big end supply, then maybe mark it so you know what's going on when you run it but the good news is it looks like you can just put it together!
Cheers Rick 

The telltale doesn't seat on anything ,it just runs in the bore.
John

Hi John
Thanks for photos.
The only different is the telltale seating has broken away at the drilling point for the rocker box oil feed.

The question is will the telltale seat, seal and do its given purpose correctly to provide oil to rocker box and big end?

Or machine a brass sleeve with lip to correct the broken seating.....

Many thanks

Regards Ian

This was with my camera.
John Hood

Sorry that the pic is not great, I'm having to use a borescope on my phone. The drilling at 9 o'clock is where the drilling for the rocker feed joins the telltale, it also carries on into the main feed between the back of the telltale and the pump gears.

Hi John
Thanks for info and look forward to picture of your tell tale oil pump housing.

Just to re-assure me of the gap on the tell tale sealing face on the casting.

Again thanks

Regards Ian

Just checked my spare pump, the feed to the rocker does drill right through to the main feed as per your drawing, and also a small opening into the face of the flat face that has been  cut away on yours.
I'll try to get a picture posted later.

John Hood

Hi Ian, I can't remember now if the rocker feed is permanently open or just first to open but it probably doesn't matter because the height of the rocker box will defeat the oil tank's head of pressure. The point where the big end feed opens is dictated by the back pressure created at the tell tale by the adjustable valve on the rocker box. I think this has been discussed in some depth on past questions about rocker box oiling.  I do have a 9A cover but it's a bit buried at present or I'd dig it out and take a look but meanwhile someone else may be able to answer that.
Cheers Rick   

Hi
Please see picture as this will explain, better then words.

I would like to confirm the oil way end point within the Tell Tale chamber for the feed to the rocker box.
Is this prior to the Tell Tale seal or before as shown in diagram.

As you can see the oil pump housing the BSP connector to the rocker box was damaged - This was rewelded shaped etc - but when the oil way was re-drilled a section of the tell tale sealing face/shoulder was damaged.

My options, as I see them to repair the Tell Tale face/seal is:-

1. Make oversized brass top hat (best description I can think off) to fit against existing tell tale seal face within pump and a lip held by the male BSP oil pipe connection. This would in theory block the damaged face where tell tale sits at rest and is held in place by interference fit and Male BSP pipe connection

Any other options??

Await remarks with interest

Regards Ian