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Thread Like Summary
Allan G, gavin eisler, Ignoramus, kevin, NickL, wbabojo
Total Likes: 10
Original Post (Thread Starter)
by jakejoseph
jakejoseph
Hi folks - installing a head for the first time on a 1967 BSA A65L. I've installed heads before, and the factory service manuals have always given guidance as to whether the bolts should be installed with lube or with not. What's best practice for these engines and installing the head bolts/studs.

Should I use anti-seize on the bolts/studs?
Should I install dry?
Should I install with 30wt.?

Any advice is welcome.
Liked Replies
by SamAdamson
SamAdamson
"other than ... a torque number is infact the loading of the stud thread ect in tension"

When a fastner is tightened down only ~10% of that torque is being converted into torsional load on the fastner with ~50% being friction under the head of the nut or bolt and ~40% being the friction of the threads. https://www.nord-lock.com/insights/bolting-tips/2019/torque-preload-friction/

If you apply antisieze or similar to a fastner this it acts as a lubricant and can drastically reduce the firction, and potentially (depending on the exact reduction in friction) significantly increase the clamping load applied to the fastner.

The coefficent of friction between unlubricated static steel and steel is around 0.8 with lubricated static steel on steel it could hit 0.16, which has the potential to triple or quadruple claimping load for the same torque applied.

This could turn your 30% of failure rate to 90 - 120% of failure rate. And as we are talking about threads which are exclusively at best 50 years old failure is a distinct possibility.
2 members like this
by Allan G
Allan G
Originally Posted by Gary E
Originally Posted by Mark Z
Originally Posted by Gary E
Spares Manuals, for A65/A50's anyway, indicate a standard thickness (1/16" or .0625" or .064") for the studs and bolts, with no washer indicated for the 3/8" short center bolt.

All of the head bolts for both of my A65s have always had what look like original washers, so I had to look at the '67 factory Spares manual, which I've owned for fifty years, and what I found was strange indeed:

One of the two rear head bolts is shown with a washer, page reference 13, P/N 2-923, and the book indicates that there are two of those.

One of the external studs is shown with a washer, page reference 15, P/N 2-2138, and the book indicates that there are SEVEN of those. That would account for the four studs, the two FRONT bolts, AND the center bolt!

This begs the question, why are the two rear bolt washers different from the rest? On further examination, I see that the two rear bolts are part number 68-338, and the two front bolts are part number 68-337. The four head bolts are the same length, so this difference in part number must be a hangover from 1965 when the two rear head bolts were 5/16" diameter! Note that that would make those two flat washers 5/16" diameter as well.

In any case, a washer on the center bolt IS indicated. Gary, where do you see washer thicknesses? I don't see that in my Spares book.
I see the quantity seven and two indication in on the pages. The two showing 5/16" washers. Should be quantity of nine for the 3/8", so a typo all the way up to and including the '69 manual. In the '70 manual, they corrected it.

The thickness is shown in the '69 & '70 manuals and on some of the big name parts suppliers.


To add to the thickening plot, the washers were upgraded again, I think the ones that come with many kits are the 0.064" thickness, though for the 823cc Thunderbolt, I made my own set as per the following. (Excuse the cropped image, I couldn't upload as a PDF)

[Linked Image]
Attached Images
2 members like this
by htown70
htown70
You need to reduce the torque specs by 25-30 percent because anti seize makes the bolt or nut easier to turn. Almost all torque specs unless specified are assumed to be on dry threads. I have rebuilt a number of engines and always use dry threads with no issues.
1 member likes this
by BSA_WM20
BSA_WM20
Actually what happens is when the head gets hot the holes collapse onto the studs / bolts depending upon which model BSA you have.
And this is why the heads refuse to come off and appear to be stuck onto the barrels because the fasteners are now being clamped by the colapsed hole
On an A65 you notice that the bolts are undone but they are still hard to pull out then when youtry to lift the head it just won't budge
Fitting washers that are too thin or not fitting them at all makes this even worse .
1 member likes this
by gunner
gunner
Anti seize compound as its name suggests is a good idea for nuts and bolts which get exposed to wet conditions and/or high temperatures, where seizure is common, so typically car chassis bolts and exhaust studs.

I don't think either of these conditions exist with the A65 cylinder head nuts and bolts, so I don't think its essential to use it, although it may be useful on the studs through the barrel as mentioned.

If you do end up using on the nuts, recalculate the torque as noted.
1 member likes this
by Gary E
Gary E
Originally Posted by Allan G
[Linked Image]
Good info. What's the date of the document?
1 member likes this
by Richard Phillips
Richard Phillips
All very enlightening but I’ll stick to ARP recommendation use of their anti seize on their engine head bolts and studs.
1 member likes this
by Ignoramus
Ignoramus
yep Allan, that is why i said "in good nick" regarding threads .... they sure have taken some misuse , most popular was threading in BSW (or a UNC for our American friends) into a BSF second only to cranking in a damaged burred bolt whilst saying " this is a tight one pass me the power bar"

all good
1 member likes this
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