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 71 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 44 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.