hi, i'm building a 1360 supercharged engine, gearbox is done and the head is almost done, but i'm wanting to put in 10th and 11th head studs in, but i'm not sure where the holes are meant to drilled, does the head gasket have the holes for the 10, 11 studs so i can copy the head gasket as a template. i have the machines to do the work but, i'm just unsure where to drill, what thread and depth should the hole be.

Are the holes already in the head? Just temp. bolt the head on and mark. Couldn't tell you depths though.

thats the problem, i would template from the head if i had one, but i don't have a head that i can use, i need my head and block to be drilled,

1275 gasket has the holes already.
When doing the head, note 2 of the gasket holes and head stud holes are smaller- use these to align it.
Use it as a template and centre punch position. CHECK BEFORE DRILLING.

Cooper S had a 5/16" UNC bolt at the thermostat end, but many people just put another 3/8 head stud in. Try not to drill too deep, you will hit the water jacket.

These holes should be drilled and tapped vertically on a milling machine or a decent pedestal drill- if the studs are crooked you will have trouble getting the gasket and head on.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

i have a full milling machine and verticle drill press, wat threat are tha ARP studs so i can match the thread. should the depth of the thread be the same as the others.

Threads in block are 3/8" UNC, just match the depth of the others for the rear one. For the front one check the height from top to the water pump cutout, then keep drill depth a little less. You will have to shorten that stud a bit to suit.

If you drill the head first you can then use it as a drill jig to spot to the block.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Is there any great advantage to drilling/tapping the extra holes?

If so can you drill a standard 12g940 head without going through the water jacket so it won't leak everywhere?

It's worthwhile if you are going to run over 10.5:1 C/R, or if it's going on an S motor and has to look kosher.
Otherwise it's just pub points.

Yes you can drill ANY 12G940 head, also the 12G1316 smog head, used on 1275LS and late 1275 Mokes. These all have metal provided in the casting for this purpose.
But NOTE- SMALLBORE HEADS DO NOT.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.