Updated cylinder head studs.

[Joeck]

I am doing a full re build on a 1098 engine and am wondering if uprated cylinder head studs and nuts are worth adding as part of this ?
I understand that the torque settings can be raised using these studs but just wanted to check that the raised torque is not likely to cause any issues.
I have checked all the threads in the block and they are all a good fit to a new standard stud.
Both head and block have checked out good for flatness.
Any advice would be very welcome.
Thanks.
Joe

[philthehill]

My advice is to throw away the standard Minor ex factory cylinder head studs and fit the better 'A' Plus head studs with flanged nuts.
The 'A' Plus studs can be torqued to 50lb f ft dry. I would advise that the revised stud tightening sequence is used. That can be found using the search facility or looking in the Morris Marina workshop manual.
You will not have any problems fitting the 'A' Plus studs and flanged nuts as they are a straight swop.
Make sure that the stud holes in the block are countersunk.
These are the studs I would use:
https://www.minispares.com/c-aht279a-he ... anged-nuts

[Bill_qaz]

viewtopic.php?p=705774&hilit=Head+stud#p705774

Phil the engine guru has posted good info previously as in above link example. You can use the search to find such info.

Phil beat me to it by a minute, a true racer

[Michiel]

Phil, personnally, I would be a bit scared if there is a need to countersunk the block as this would mean the threads are damaged?

[philthehill]

There is absolutely no need to be scared about countersinking the stud holes in the block.
We are not talking about serious countersinking just countersinking enough to remove any existing pull up of the stud threads in the block.
The pull up of threads can cause the cylinder head gasket not to seat around the studs so leading to head gasket failure.
Countersinking the stud holes is a common and well practiced process.

countersunk studs.jpg (348.39 KiB) Viewed 234 times

[Michiel]

Thanks you for your reply. I did not mean the act of countersinking (if that is a word) the block, that seems harmless. I meant that if a countersunk is needed than the tread in the block must be damaged (where else is the material of the ridge around the hole come from) and or the stud's thread is stretched?

[les]

You are in fact removing what you call ‘damage’ by countersinking slightly. It’s not really damage as such.

[svenedin]

Yes, the very first part of the stud thread in the block can get "pulled up" meaning that being under tension over many years the thread becomes raised above the surface of the block. Phil warned me about this when I did my cylinder head gasket and I am grateful that he did. When I cleaned off the surface of the block with a mounted blade (a window paint scraper) I could feel the blade catch on the pulled-up threads. This is subtle but it could affect the sealing of the head gasket. Countersinking removes an absolutely tiny quantity of metal and there is so much more thread in the block that it is irrelevant in terms of "damage".

I do have a photo somewhere and will hunt for it. I am sick at home with Covid so I have nothing better to do!!!

Stephen

[svenedin]

A "pulled-up" thread

IMG_9362.jpeg (213.82 KiB) Viewed 207 times

[Michiel]

I see. But previously it was torqued up as per the MM WM?

[unclealec]

I come across this regularly with Riley engines.
I call it "volcanoing".
I gently run a fine-cut bias file across the top of the block and, by delicate touch, gently file down the volcanoing without scoring the block face.
On Riley engines I have a worryingly thin block top face that lends itself to studs pulling out hence the reluctance to countersink.
I don't recall this as being a problem with the handful of A series blocks I have built up.

[Joeck]

Thanks for all the information it’s, as always, very useful.
I have now ordered a set of studs/ nuts from mini spares and will refer to the new tightening sequence once they arrive.
Thanks again.
Joe.

[philthehill]

The pulling up of the block threads is a natural progression as the block gets older and many blocks are nearly as old as me. Basically no different to both of my knees getting older and wearing out at the ripe old age of 75 (I am now 77) and having to have them replaced - I would not call them damaged. It certainly gets the conversation started which soon moves onto classic cars especially Morris Minors. Surprising how many classic car drivers have had their knees replaced and can be identified by their knee zips.
I do wear my knee zips with a certain pride as my original knee joints carried me through thick and thin and over many miles.

[oliver90owner]

It’s likely not related to deeper threads than the first. The studs may stretch from that first thread, hence pulling it very slightly every time the head is tightened down. Also, those studs are inserted into the block threads until the threads run out on the studs, tightening in the stud with no more thread may well displace metal, rather than pulling it up - the metal has to go somewhere as the unthreaded stud is pulled into the block.

[philthehill]

The studs should be tightened no more than hand tight when being screwed into the block.
The threads in the block should be run through & cleaned with a used plug tap before fitting the studs.
Using a new plug tap may result in thread metal being removed so weakening the thread. A good way of cleaning the threads is to use a cylinder head stud that has had a flat ground on it to below thread root. The edge of the flat cleans and very lightly reforms the thread if there is any distortion of the thread. Grease the used tap and stud before inserting into the stud hole. The grease will pick up any crud from the stud hole.

[les]

tightening in the stud with no more thread may well displace metal, rather than pulling it up - the metal has to go somewhere as the unthreaded stud is pulled into the block.
[/quote]
Yes that’s more likely than a thread pulling up, as the complete thread is one unit, rather than separate threads.

[philthehill]

Les
Some of those threads that have pulled up go right through to the water jacket i.e. do not have a bottom.
Also if the stud is tightened by hand and it will not go in sufficiently far enough then that is a good indication that there is something wrong with either the stud or threads in the block.
The ARP cylinder head studs as fitted to my engine specifically say in the fitting instructions 'do not tighten more than hand tight'.
Phil

[les]

I didn’t know studs were to be put in hand tight, the post before mine mentioned if the stud was tightened past its thread that could cause metal to raise/be displaced. I think thats a possibility. However in light of what you say about tightness, that couldn’t happen.
In the past I’ve tightened studs using two nuts locked together. I’ve learnt something today Phil !

[philthehill]

Les
The problem is that the blocks are now so old that I suspect that many of the studs were fitted in the past as you describe. In fact that is how I used to fit them until I learnt better.
Phil