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Discussion Starter #1
1998 4.6L Gems

One of my exhaust manifold to head bolts sheared, and so I thought I may as well replace the whole set of 8. But everywhere i look they reference a 12 point M8 bolt ERR4961. But mine are 12 point and M10 - there's no sign anyone ever drilled out from 8mm to 10mm, although this 4.6L engine may have been a replacement 10 years or so back. Is an M10 bolt standard on some other model/ later?

Rgds, Rob
 

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1995-2002 Range Rover P38A
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They should be around 5/8 th if I remember correctly, I can pop you one in the post, clean the others with wire brush on drill, then nice coat of oil
 

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GEMS are Imperial, Thor are M8, so on a '98 they will be UNC Imperial sized ones, smaller than M10. Can't for the life of me remember the size though although they could be 3/8 UNC (as that works out to just over 9mm).
 

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Just checked, they are the same thread as the inlet manifold bolts and they are listed as 3/8 UNC for GEMS and M8 for Thor.
 

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Discussion Starter #5
Now why didn't i think of that - good detective work Richard and Chris. Even now that I know what I'm looking for they're like rocking horse doings, in 12 point. I'm going to have to take you up on your offer Chris, I think. I'll PM you
 

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A few people have replaced them with stainless Allen bolts, less chance of them seizing in and it makes getting that painful one at the rear on the RH bank out easier. I'm not even sure why they are 12 point, normal 6 point would still do the job and are far easier to get hold of.
 

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30 year ago I had an FJ40 Landcruiser and it also had steel studs and brass nuts. A mechanic guru told me that the dis-similar metals won't corrode onto each other and are easy to remove.
I don't know if Stainless etc into the aluminium heads would act the same way but it might be something to consider. Just a thought.
 

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Discussion Starter #10
I agree Rowant. I'm a big stainless fan in non load bearing applications, but not direct to aluminium. It is also has a different thermal expansion coefficient from engineers' spec, so I shall leave well alone
 
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