Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Anti Seize on Head Bolts/Studs - 1967 BSA A65

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.

I always us a little anti seize on the bolts and studs into the barrel.

anti seize ( copper silicate) definitely for this,,, if you dont have any graphite grease is pretty good as well. I always use just a hint of never seize copper silicate on both faces of the gasket ... dont know if it does much other than make me feel better but it does help removing the gasket latter.

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.

back when i worked wellhead in th eoil fields, i had manuals for the flanges holding the valves in the frac stack together. the nuts often went to 1800 pounds-feet or better, and i had numbers for all the different torque settings required by different types of anti-sieze lubricants. all were significantly less than dry and all were significantly different from each other.

in general, if not specified, the torques settings in our manuals are for clean, dry threads. no oil and no anti-siezes.

Copperslip or similar on the plain area of the head/barrel bolts and/or studs
makes removal a hell of a lot easier. Leave the threads alone though.

You should only use what the manual says, which is usually clean degreased threads. If you want to use antiseaze where it isn't specified make sure you recalculate the required torque which will need to be reduced, you will need the K nut factor from the lubricant and the K nut factor for the unlubricated fastner. then calculate the lowered torque setting using T=KFD, (where T= torque, F= clamp load, D= nominal diameter of bolt and K= nut factor).

If you don't take this into account you will increase the clamping load and will be at risk of stripping or damaging threads.

For simplicity i would always stick with what the manual says.

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 .

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.

Page B3 of the 1971 WSM exploded diagram shows washers under all the head Fasteners, the centre bolt with washer is shown there
Page B3 in the 1970 manual, same.

Page 15 of the haynes manual shows the same image as the parts book, , only one stud and one bolt is shown with a washer, the rest omitted .

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.

Use on spark plugs. Just tighten enough to crush the washer.

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.

Note that there are multiple types of anti-seize lubricant. For spark plugs, use only the type that's specified for that purpose.

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.

"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."

A typo sort of, but it was correct for 1965; they just neglected to update the book until 1970.

Funny, the subtle things you don't notice even after having owned and studied a book for fifty years!

having looked at some of the remarks regarding dialing back the torque setting if you use some thread "additive" what can i say ?

other than ... a torque number is infact the loading of the stud thread ect in tension

Due deference is given to Trevor who correctly pointed out that collapse of the ally ect makes if seem like the head is stuck. . alloy , compression of the ally// NOW that is why i have for years run a 0.5 or so drill through the holes while im have it on the bench ,,, problem solved for ever .


someone suggested that stripped threads busted bolts et al could eventuate ....i suggest that an examination is made into the force required to strip around 1/2 inch of BSF in cast iron of SOUND thread . Just of the top of my head i would bet that a pound to a pinch of *hit that the max torgue in book would only be ?? ....what??? .... 30% of the failure point. It takes a lot to tear 15 or whatever threads out of cast iron ... to bust the bolt you would have to bottom it out. or be using an already distressed bolt.

what is not conjecture however is that if (when) alloy takes up a "set" it will have technically lost height so your torques settings will again reduce,

but what are the alleged consequences of a few % less? ( and spare me the lectures about design parameters) ... blown head gaskets or at least leaking and possible head distortion...

the consequences of "over torqued" ( which i dispute) ... um that would be nothing ? ...right?

But so Y'all please remember that i am a chap who has never even owned a torque wrench ( nor had a bolt let go in service)

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)

Good info. What's the date of the document?

I actually did this on the office PC, but I’ll have a look for you when I get back to it.

September 1970

"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.

All very enlightening but I’ll stick to ARP recommendation use of their anti seize on their engine head bolts and studs.

30% failure rate ? .... as I said in my post I have never had a bolt that I have used lube on let go in service so i guess thats just blind luck eh

so lets pretend here on Fantacy Island that there are 9 head bolts.... at 30% about 3 are going to fail . How ridiculous

IF however "This could turn your 30% of failure rate to 90 - 120% of failure rate." I am relived to know that because 120 % of ZERO is ZERO ...mind you I am interested to know how at 120% you have more bolts failing than fitted? Do the spares in the bag break in sympathy?

isn't the internet wonderful ... a bazar highly technical piece of tripe for all occasions probably written by some youth whit a PHD in mechanical engineering who has never held a spanner in his life .

I will at once rush to my bikes and repair all the broken bolts and striped threads ( that , by the way was sarcasm)


Further more here's a quote from the link you posted (even if their mathematics are wrong!)

"It is commonly known that the scatter in achieved preload is +/- 30%. This means that the maximum possible preload can be twice as much as the minimum possible preload. Scatter can be even higher for rusty bolts or for stainless steel Fasteners, which are prone to seizing.

Luckily, scatter can be decreased by applying lubricant or using bolts with a specified coefficient of friction, for example with a top coat or wax."

I think I read that differently to you,

My interpretation was this…

If you apply lube to a bolt (where non was previously specified) and then torque up to 30ft/lb (or what ever the instructions for the bolt and rod, or just bolt if it’s cylinder head specified) then you have infact stretched the bolt length by a greater amount. Probably an equivalent to tightening a dry bolt to say 45 ft/lb as far as stretch is concerned.

It’s that stretch that determines how much your 12.9 grade bolt has diminished by, if that given stretch is beyond that of the bolts capability. (Bolt sizes and metal grade types vs max torque factor can be found on line).

So by stretching the bolt beyond its limit, you may have then reduced its maximum torque value by 30% or what ever.

If it’s cylinder head bolts then the likely hood is, if the bolts are decent quality with rolled threads then the threads in the cast iron barrel will fail first.

If it’s rod bolt then, I’d rather not take the chance and do what ever the instructions say, for both rods and bolts, depending on whether they are new rods supplied with the bolts (like map or Thunder where by the bolt threads into the rod itself) and thus bolts were supplied with the rods, or just the rod bolt specification if the bolts go through the rod and into a nut (like the original setup)