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Torqueing down the cylinder head
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Miken



Joined: 24 Dec 2012
Posts: 415

PostPosted: Wed Jun 23, 2021 5:21 pm    Post subject: Torqueing down the cylinder head Reply with quote

Nearly 11 months ago I got my pickup truck on the road after refurbishing the engine. The A40 engine is very similar to (and was later developed into) the BMC B-series engine. During the running in period i tightened down the head in accordance with the manual.
Now , coming up for a year and over 4000 trouble free miles later, I am wondering, should I:-

A) apply the torque wrench again to see If anything moves.
Or
B) leave it alone and stop worrying.
What do we think?
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Rick
Site Admin


Joined: 27 Apr 2005
Posts: 21899
Location: UK

PostPosted: Wed Jun 23, 2021 6:09 pm    Post subject: Reply with quote

Well a) I would have thought it'd all be fine, however b) these engines are a little prone to blowing head gaskets, so re-checking won't take long and might save an unfortunate breakdown.

RJ
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Rick (OCC Admin)
Various 1920s-1960s - Austin, Morris, Commer, Dodge etc.
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Keith D



Joined: 16 Oct 2008
Posts: 1037
Location: Upper Swan, Western Australia

PostPosted: Thu Jun 24, 2021 6:09 am    Post subject: Reply with quote

After 4000 miles with no trouble, I would be inclined to leave well alone. You may well find that when you re-torque, the nuts will not move easily as they have 'frozen' in place over the last year and may not reflect the true reading on the torque wrench.

Keith
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1926 Chrysler 60 tourer
1932 Austin Seven RN long wheelbase box sedan
1950 Austin A40 tourer
1999 BMW Z3
Its weird being the same age as old people.
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Miken



Joined: 24 Dec 2012
Posts: 415

PostPosted: Thu Jun 24, 2021 8:43 pm    Post subject: Reply with quote

Keith, I know you've owned your A40 for many years more than me, so I will take your advice and leave it alone.
Thanks,
Mike.
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ukdave2002



Joined: 23 Nov 2007
Posts: 3706
Location: South Cheshire

PostPosted: Fri Jun 25, 2021 8:13 am    Post subject: Reply with quote

If during the rebuild you used new head studs, the head and block were surfaced or known to be flat and no lubricant was used when originally torqueing up, then I'd leave well alone.

If no to any of the above, then its probably worth checking, especially if the studs were not new, as used studs can be less predictable in how they stretch.

If you do re-torque back the nuts off half a turn before tightening up again.

Dave
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Miken



Joined: 24 Dec 2012
Posts: 415

PostPosted: Fri Jun 25, 2021 9:32 am    Post subject: Reply with quote

ukdave2002 wrote:
If during the rebuild you used new head studs, the head and block were surfaced or known to be flat and no lubricant was used when originally torqueing up, then I'd leave well alone.

If no to any of the above, then its probably worth checking, especially if the studs were not new, as used studs can be less predictable in how they stretch.

If you do re-torque back the nuts off half a turn before tightening up again.

Dave


Yes to all that.
Also the company that machined the joint faces had in stock and sold me a couple of genuine NOS proper copper/asbestos gaskets that he had in stock and are now hard to find. I'm told that the modern substitute used in gaskets isn't as good as the old type. New studs and nuts came from the OC.
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ukdave2002



Joined: 23 Nov 2007
Posts: 3706
Location: South Cheshire

PostPosted: Fri Jun 25, 2021 3:56 pm    Post subject: Reply with quote

Miken wrote:
ukdave2002 wrote:
If during the rebuild you used new head studs, the head and block were surfaced or known to be flat and no lubricant was used when originally torqueing up, then I'd leave well alone.

If no to any of the above, then its probably worth checking, especially if the studs were not new, as used studs can be less predictable in how they stretch.

If you do re-torque back the nuts off half a turn before tightening up again.

Dave


Yes to all that.
Also the company that machined the joint faces had in stock and sold me a couple of genuine NOS proper copper/asbestos gaskets that he had in stock and are now hard to find. I'm told that the modern substitute used in gaskets isn't as good as the old type. New studs and nuts came from the OC.


Don't go broadcasting who sold you the asbestos gaskets, since 2006 they can be fined 2000 per item sold! you can't even give the stuff away in the UK.
We had to dispose of as load head gaskets together with brake linings for the MR, we kept one of each where we required a pattern, didn't feel right disposing of good NOS, however when you see or here of folk affected by it there is some perspective.

Dave
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Miken



Joined: 24 Dec 2012
Posts: 415

PostPosted: Fri Jun 25, 2021 4:38 pm    Post subject: Reply with quote

I wont, I wouldn't want to get anyone in trouble.
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