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Ray White
Joined: 02 Dec 2014
Posts: 6319
Location: Derby
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 Posted: Tue Feb 11, 2020 7:41 pm Post subject: Head stud question |
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| There may or may not be a correct way to install cylinder head studs into a block, however, as they come with more threads on one end than the other I would have thought someone might have an explanation.? |
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Salopian
Joined: 05 Jan 2010
Posts: 354
Location: Newport Shropshire
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| Posted: Tue Feb 11, 2020 9:13 pm Post subject: |
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I have always put shorter threaded end to block but why is lost in the mists of my youth!. Do always check threads are clear as have seen a block split by a stud screwed into a hole with oil left in.
Suppose you need a little more leeway when fitting the head which may involve washers a degree of skimming various gasket thicknesses etc.
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Alvis SD 12/50 1928 MG TD 1950 |
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Ray White
Joined: 02 Dec 2014
Posts: 6319
Location: Derby
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| Posted: Tue Feb 11, 2020 9:30 pm Post subject: |
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| Salopian wrote: | I have always put shorter threaded end to block but why is lost in the mists of my youth!. Do always check threads are clear as have seen a block split by a stud screwed into a hole with oil left in.
Suppose you need a little more leeway when fitting the head which may involve washers a degree of skimming various gasket thicknesses etc. |
I would imagine your theory is correct. Also, there may be a range of heads for a given engine. Perhaps some aluminium heads are thicker. Sometimes accessories/brackets etc are fitted to the head.
If you look on line there are examples of the reverse practice with the extra threads in the block. I would be concerned that it could lead to breaking through into the water jacket. Then again, I have come across engines where this is the way they were built in the first place. (Jaguar XJ6). |
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ukdave2002
Joined: 23 Nov 2007
Posts: 4105
Location: South Cheshire
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| Posted: Tue Feb 11, 2020 10:21 pm Post subject: |
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Ray
Rule of thumb; depth of thread for a stud into the casting should be 1.5x the diameter of the stud. On these older castings you want avoid the bottom of the stud hitting the casting as they can break through into water passages, so the studs are normally made so that all the thread can be screwed in before the end of the stud touches the casting.
Dave |
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Ray White
Joined: 02 Dec 2014
Posts: 6319
Location: Derby
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| Posted: Tue Feb 11, 2020 11:58 pm Post subject: |
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| ukdave2002 wrote: | Ray
Rule of thumb; depth of thread for a stud into the casting should be 1.5x the diameter of the stud........
Dave |
That's something I haven't heard before and I will remember it for the future.
Thanks Dave. |
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Miken
Joined: 24 Dec 2012
Posts: 544
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| Posted: Wed Feb 12, 2020 8:01 am Post subject: |
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I was taught 1.5 x dia. In iron
2 x dia. In ally alloy
1 x dia. In steel (actually it's the thread core dia.) Which is why steel nuts are the thickness they are.
Any more thread length gives no more advantage. |
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colwyn500
Joined: 21 Oct 2012
Posts: 1745
Location: Nairn, Scotland
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| Posted: Wed Feb 12, 2020 9:10 am Post subject: Re: Head stud question |
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| Ray White wrote: | | There may or may not be a correct way to install cylinder head studs into a block, however, as they come with more threads on one end than the other I would have thought someone might have an explanation.? |
I was advised to use "studlock" on the threads into the block. This gives a waterproof seal where stud-tappings are bottomless and into the water-jacket, helps against corrosion in any case, helps to even out the loading on the threads when under torque and does the obvious in resisting the stud self-loosening. The studs and internal threads obviously need to be grease-free.
That was on an Austin Ten where the shorter threaded end also goes into the block and the advice was from a respected expert in the Club. |
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Ray White
Joined: 02 Dec 2014
Posts: 6319
Location: Derby
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| Posted: Wed Feb 12, 2020 12:28 pm Post subject: |
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I can see the advantage of sealing a stud where it has broken through into a water passage but in some cases like the later 4.2 XKE Jaguar engines that I mentioned earlier, it is a design feature. A very poor one in my opinion (but what do I know?)
Here are said studs.
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ukdave2002
Joined: 23 Nov 2007
Posts: 4105
Location: South Cheshire
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| Posted: Wed Feb 12, 2020 1:16 pm Post subject: |
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Presume you will be replacing them  |
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colwyn500
Joined: 21 Oct 2012
Posts: 1745
Location: Nairn, Scotland
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| Posted: Wed Feb 12, 2020 1:21 pm Post subject: |
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| Ray White wrote: | it is a design feature. A very poor one in my opinion (but what do I know?)
Here are said studs.
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I agree with you on that and it was likewise with some of the studs on the Austin Ten and probably many other cars. The lack of water is one of the many reasons why I love my air-cooled Fiat.  |
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Ray White
Joined: 02 Dec 2014
Posts: 6319
Location: Derby
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| Posted: Wed Feb 12, 2020 1:38 pm Post subject: |
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| colwyn500 wrote: |
The lack of water is one of the many reasons why I love my air-cooled Fiat. |
A love shared by millions of motorcyclists and VW owners I am sure. |
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norustplease
Joined: 11 Apr 2011
Posts: 779
Location: Lancashire
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| Posted: Wed Feb 12, 2020 6:15 pm Post subject: |
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And classic Citroen owners too.
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Ray White
Joined: 02 Dec 2014
Posts: 6319
Location: Derby
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| Posted: Wed Feb 12, 2020 6:16 pm Post subject: |
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| norustplease wrote: | | And classic Citroen owners too. |
...and bubble car fans... |
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Mog
Joined: 30 Dec 2007
Posts: 661
Location: Sydney
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| Posted: Thu Feb 13, 2020 7:52 am Post subject: |
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| I agree with Miken and his sizes of studs in different materials . The dia. of the stud or root diameter is the weakest point . |
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ukdave2002
Joined: 23 Nov 2007
Posts: 4105
Location: South Cheshire
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| Posted: Thu Feb 13, 2020 9:27 am Post subject: |
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It never ceases to amaze me how often head studs get reused when their age or number of re- torque cycles is unknown. Unless one knows their history they should be treated as consumable and changed when the head gasket is replaced.
Dave |
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