S head stud length

[Andrew1967]

Just fitting the head studs to HOY's engine block and noticed that some of the shorter studs are a different length

Some are measuring 4" and others about 4 1/8" .

Which is correct ?

[Supersonic]

Andrew, all the 1275cc Cooper S studs I've measured were short x 6 No (102 mm) 4 inches and long x 4 No (140mm) 5.5 inches. I can't remember from the top of my head what length the small bolt is

Alan

[Andrew1967]

Thanks for the reply Alan

I thought the short ones were 4” but some of these are 1/8” longer and sit higher.

Whilst it might not sound a lot it will definitely show when the head is on and washers/nuts fitted.

I dare say the cylinder head bolt police will detect different amounts of thread showing

Couple pics attached. One shows the actual lengths top to bottom, the other the effect when both are screwed into the block ..

[bmcman.ie]

Get a few pints into you andrew, they will all look the same then!

[GraemeC]

Are they both the same marking on the top?

Probably just down to stud manufacturer's production differences at varying times, probably more than one supplier over the years.
I'm sure the collective will be able to muster up enough of the same size for you.

[Andrew1967]

Hi Graeme,

I was just about post about that very thing ..

I've just taken some studs out of a spare 1275 S block and they are all of 4" dead length and all have a small drilling in the centre of the top of the stud. The 'longer' short ones do not have these.

I now seem to recall talk about this some time ago on the forum.

Are the studs with the drilled hole in the top S studs ?

I have enough of these now to make up a set but would be interested to know what the marking denotes, if nothing than a manufacturers marking.

[bwaminispeed]

The dimpled ones are better quality/stronger, and, I believe were used across the range when introduced......

[AndyPen]

I can't get to mine at the moment- but I'm sure they had a dimple on my 970S.

[Andrew1967]

Dimple .. that's the word I couldn't think of when posting up earlier

Thanks for the posts guys

[iain1967s]

Is maybe the 'longer' short stud intended for the water tap end of the head, where the coil bracket attaches on later engines?

[Maddog]

In Australia at least, I believe there were improved strength studs, marked with the dimple. I also believe that there were two different lengths of studs between small bore and big bore engines (although it is unclear to me why as the heads are all the same nominal thickness). Spider might be able to elaborate? I read a post about this topic somewhere recently, but can't put my finger on it right now...

[ricardo]

The reference to the small bore studs being shorter was here: viewtopic.php?f=3&t=27381&start=30

[Maddog]

Thanks Ricardo - that was it, and also explains exactly why the difference in length - deeper engagement into the block deck on the big bore motors.