USHM3 Cylinder head bolts

for those with Series MM sidevalve cars produced between September 1948 and February 1953
Mick Lynch
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USHM3 Cylinder head bolts

Postby Mick Lynch » Fri Mar 19, 2021 2:36 pm

Just idle curiosity but I notice ESM supply the cylinder head studs in three lengths.
I’m wondering what is the significance of this, if any.

I have a USHM3 and I’ve just measured mine... all 13 are the same.

**bolts should read studs in subject**

RobThomas
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Re: USHM3 Cylinder head bolts

Postby RobThomas » Fri Mar 19, 2021 7:31 pm

Nearest the dynamo are shortest, nearest the exhaust are longest. Got a photo of your engine?
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Mick Lynch
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Re: USHM3 Cylinder head bolts

Postby Mick Lynch » Fri Mar 19, 2021 8:09 pm

RobThomas wrote:
Fri Mar 19, 2021 7:31 pm
Got a photo of your engine?
Here... although it does not do it justice.

Studs are 60mm above block man and boy with one exception near the dynamo and that’s 65mm
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39B6496B-EA0F-41BB-A05A-0A2C541328D3.jpeg
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RobThomas
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Re: USHM3 Cylinder head bolts

Postby RobThomas » Sat Mar 20, 2021 10:06 am

Someone might have cut up some long M10 bolts to make those? Original heads had studs and deep nuts that left just a couple of threads exposed in each position. Not the end of the world to use them as they are, so long as they are spacered out enough. Other options are out there since a few modern cars use the same thread pattern.
studs1.jpg
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These ones are from a Le Mans Aston Martin. Hellishly expensive when new. These were unused ones I got cheap in a large quantity.
Cardiff, UK

RobThomas
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Re: USHM3 Cylinder head bolts

Postby RobThomas » Sat Mar 20, 2021 10:06 am

studs2.jpg
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Cardiff, UK

Mick Lynch
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Re: USHM3 Cylinder head bolts

Postby Mick Lynch » Sat Mar 20, 2021 4:30 pm

Nice.

I’m thinking I probably need new ones. Closer inspection shows they are quite pitted, not as good as your ‘old’ stud in photo. I think you’re right about them being cut and one has thread much longer than the rest. M10 you say?

RobThomas
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Re: USHM3 Cylinder head bolts

Postby RobThomas » Sun Mar 21, 2021 9:32 pm

Can't be 100% certain but I think M10 std, not M10 fine. HT nuts were easy to find but not deep ones. They'd have metric head sizes rather than Whitworth so may be worth saving your old nuts.
Cardiff, UK

sirrom918
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Re: USHM3 Cylinder head bolts

Postby sirrom918 » Thu Mar 25, 2021 9:11 pm

I've been messing about with Morris 8hp engines - 1935 to 38 Morris Eight Series I and II, 1939 to 48 Series E and the Centurion Tank generator engines based on the Series MM Minor USHM3 block for almost 50 years. The head stud threads on all of them are M10 x 1.5mm pitch. As Rob Thomas says the original cylinder head nuts although metric thread had Whitworth hexagon heads. As you already know, ESM stock both the studs and nuts.


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