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MG Midget and Sprite Technical - additional holes in 12G940 head?

I've got a 12G940 head which i bought separate from my 1275cc engine, it has one extra hole on either side of the rocker cover, are they standard or are they for additional head bolts and if so can I just ignore it as is? The block doesn't seem to have the same holes but the head gasket did.

Also under the thermostat housing is a take of for something that i don't recall were there on my original engine is that for the temp gauge and can I just plug it up?

Thanks Alex
Alexander Sorby Wigstrom

One hole at the thermostat end and one at the opposite end?

This is commonly called the 11 stud head as fitted to the Mini Cooper 1275 S and also the Austin 1300GT and I think MG 1300 and Riley 1300 cars. You might also find '12G1805' on the flat area by the thermostat.

It's called the 11 stud head but in reality it's 10 studs and 1 bolt.

Highly saught after for it's Mini 1275 Cooper S connection.

The 2 extra holes can be ignored.

I think the extra hole you found is for an electrical type temperature sender used in Mini and Austin 1300 applications.

Rob
Rob aka MG Moneypit

Theres a good chance your intake valves are bigger... stock is 1.3 inch, this head could well have 1.4 inch

The only issue I might have if it were leap year and the date was feb 28th... the 2 extra holes in the head may harmonize when the head is bolted to the block

But probably worrying about anal probing from martians would be time better spent then your head harmonizing from these 2 extra holes

Prop

Prop and the Blackhole Midget

It could be a standard 12G940 head that has been drilled, of course.

The take-off you describe is probably the temp gauge hole.

Some early A-series engines didn't have a hole for the sender. Early Spridgets had the temperature sender in the radiator, even though some of them had the hole in the head, plugged.

Later Spridgets had the sender in the head. The crossflow radiator had no provision for a sender.
Dave O'Neill2

"It could be a standard 12G940 head that has been drilled, of course."/

Just like one of mine is.
Lawrence Slater

I may be mistaken, but I thought the bolt at the front went through the coolant cavity, so if you leave the bolt out you will lose a lot of coolant. And don't tighten the front bolt to the same torque as the head nuts (don't ask me how I know!).
Jonathan Severn

"I thought the bolt at the front went through the coolant cavity,"

Only if someone drilled into it. It's not supposed to be open to the cavity.
Lawrence Slater

Certainly fitting an 11-stud head to a small-bore block, the front bolt does end up in the water pump cavity.

On my A35 948 engine, I had to shorten the bolt, too.

Dave O'Neill2

IIRC the front bolt does go into the water passage in the block even on a 1275 but when I had the block drilled for the 2 extra studs the machinist fitted a stainless steel helicoil to aid future removal to the front tapping. I don't know about the head but I would expect the bolt passes through a column in the head.
David Billington

The bolt doesn't go through a water passage in the head, so it's OK to use an 11-stud head on a 9-stud block.
Dave O'Neill2

I drilled my own 1275 Sprite blocks, and didn't enter the water jacket at all. I used my 1300GT head as a guide. I bolted it onto the blocks, and drilled down to the depth needed to take the bolt, and then tapped the thread. It's never leaked. In fact on my current engine(soon to be rebuilt) I snapped the bolt and took it out.
Lawrence Slater

This thread was discussed between 27/03/2014 and 28/03/2014

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