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Here's the next problem to appear with the engine on the rally car

As it warms up I notice coolant bubbling slightly from the (extra) stud nearest the thermostat housing.
I remove the nut and the flow increases a little, I remove the stud and create a fountain of liquid that wouldn't look out of place in Trafalgar Square.
Now the block is a 1275GT item that has had the extra stud holes added (they are both the 3/8" size (ARP) studs not the Cooper S smaller stud and bolt). I notice that the front one is very close to the water pump area but is it normal to have broken through into the coolant jacket like this or has the machinist drilled too far?

Is the answer as simple as sealing the stud thread in the block with Loctite or am I stuffed?

sounds like they have broken through into the water jacket.

best to have the head off and see if there is alot play in the threads if there's alot might be worth pluging it off and redrilling. if its a little use lockite or something see if there works

The S one as you have pointed out is smaller, 5/16" unc and helicoiled. The extra stud hole when tapped probably went into the water pump area. So drain the engine, dry the stud threads and put the stud in with some Loctite sealant . Then fit the nut and retorque , then leave it for a day to set.

Fairly common for these to break through in to the water jacket (a few Cooper S Blocks I've had here over the years were like that from the factory). Not an issue, but as some later insurance, you want to coat the end of the stud with something to prevent it rusting in there as well as sealing as the other guys have said.

The other thing to be very careful of is regardless of the block type, and whether a stud or bolt is fitted, Torque to a maximum 25 ft/lbs. The Deck is rather thin here, torquing any higher than this will only warp it.

With both the S and 1300GT blocks, all of the ones I have seen have the drilling for the 11th 'head bolt' going right through into the waterway, and as Spider says were factory fitted with helicoil for 5/16 UNC threaded bolt.

Also several of the bolts I have seen had what looked like alloy washers fitted - this was maybe deliberate to help prevent leaks from this point? The alloy washers deform, but at 25lb-ft on a coarse thread does not seen to matter too much.

Also for torquing down 11th stud (where 3/8 fitted) then worth bearing in mind that 25lb-ft on the fine 3/8 UNF nut gives more clamping force than 25 lb-ft on a 5/16 UNC thread...

As Carbon says, all the S blocks have the thread through into the water pump area. These bolts seem to be the most abused thing on the Cooper S engine, I've rarely seen an original block with the original thread insert intact. The last one I had to repair was a right mess, had to put it on the mill and machine it out to 1/2"unf to clean it up, then counterbored the top face to take a new thread insert made from a Unbrako caphead bolt, this was loctited in place and the bottom was ground off to clear the water pump. Must be the only S block with a blind hole for the bolt, it's running again in a forum members car

another related top tip is that on a 970/1071, the head stud can bottom out and catch the impellor..........


guess how I found out

Thank you all for such comprehensive answers and reassurance. I'll put the engine crane away again for now.

Spider wrote:The other thing to be very careful of is regardless of the block type, and whether a stud or bolt is fitted, Torque to a maximum 25 ft/lbs. The Deck is rather thin here, torquing any higher than this will only warp it.

This is something I'd not thought of, good point. Hopefully I havent already caused the damage.
Is it possible that, as I'm using 3/8 stud then the torque would need to be a little higher to achieve the same tensile load as the 5/16 bolt at 25 lbft?
Approximately 30 lbft by my calculations.

Bob , thats exactly how I repair them , you know its real mess when you are out to 9/16" UNF

Lakeland - your estimates for the torque setting for the 11th stud are right.

According to this data : http://www.almabolt.com/pages/catalog/b ... torque.htm

A 5/16 UNC bolt torqued up to 25lb-ft will give clamp load of 4,900lbs

For a 3/8 UNF nut then torqued down at 30lb-ft will give clamp load of 4,800lbs