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Posted By: DavidP Stretched head bolt - 02/02/21 6:00 am
When I removed the head from my 71 A65 one head bolt was seriously stretched.
I believe that it's the TS rear bolt, but I might be misremembering.
Any idea on what caused this, just one bolt?
Posted By: Allan G Re: Stretched head bolt - 02/02/21 11:59 am
What about it tells you the bolt has stretched?
Posted By: Mark Z Re: Stretched head bolt - 02/02/21 2:52 pm
If the bolt is indeed stretched, it would be most likely from over-tightening or poor metallurgy.
Posted By: DavidP Re: Stretched head bolt - 02/02/21 4:28 pm
Originally Posted by Allan G
What about it tells you the bolt has stretched?
Perhaps its appearance?

Attached picture BadBolt.jpg
Posted By: Allan G Re: Stretched head bolt - 02/02/21 4:57 pm
Originally Posted by DavidP
Originally Posted by Allan G
What about it tells you the bolt has stretched?
Perhaps its appearance?


Well, I have never seen that before. Even when I have threaded up my own headbolts. They must be made of some real shite steel and just black jappaned to make them look like decent high tensile bolts. I have had barrel threads fail (which is what made me wonder if the bolt was the issue or not), All the non stud threads on my 68 barrel have got helicoils in, (I think about 3 were bad and I did those and the other 2 as a matter of prevention over cure)

There is some rubbish on the market which is why I started doing my own... Till I found the SRM ones were better than what I was threading up...... Now I use theirs.
Posted By: Ignoramus Re: Stretched head bolt - 02/02/21 5:02 pm
MY money would be on it being an aftermarket bolt not made out of high/medium tensile steel ?

compare any markings on the heads of the good bolts to this one and see if they are different, a pic of the head of the stretched one and a good one side by side would be interesting

but you were lucky it didnt bust off inside the thread ...the way it has necked down it was sure close to doing that

by the way the necking is typical of freemachining / mild steel that has passed its yield point in tension

another quick (not definitive ) test is hold the bolts lightly by the head and hit the bolt lightly with another piece of bar ....an high tensile will give a pinging type sound and mild will give a deader almost thud sound ....if the sounds are different you can be 90% sure they are different material
Posted By: DavidP Re: Stretched head bolt - 02/03/21 4:49 pm
I'm pretty sure that the bolts are after market, they have the correct BSF thread but the heads are 9/16" AF. I never thought twice about that because I wrongly assumed that BSA changed to Unified, as did Triumph.
I've bought new head bolts, but it looks as if I will need to repair the threads. The holes are wallowed out at the top, even with the new bolts fully in I can wiggle them about.
Are the coil type inserts adequate for this?
Posted By: Ignoramus Re: Stretched head bolt - 02/03/21 5:07 pm
Well the helicoils would be going into cast iron so they SHOULD be ok .... it sure isnt ideal unless you can get nice long ones ....i have no idea if you can get them in different lengths. only ones ive seen are quite short.. i never use them, but thats only cause im too mean to buy the whole kit just to do one thread....are all of the threads "wallowed " ?

My 70 is BSF so yeah after market 'soft " bolts is the answer ...dont be tempted to re use the "good" ones save then for a less important application that needs a BSF bolt.

Off the top of my head (pun intended ) i dont think thee will be enough metal between the edge of the bolt hole and the pot to accommodate a tread insert so you might be stuck with helicoils ....... shop around for some LONG ones .... some one here will know where , i dont
Posted By: Allan G Re: Stretched head bolt - 02/03/21 8:20 pm
As mentioned earlier I helicoiled mine. Since doing that I haven’t suffered with any oil weeps from the head gasket after wringing its neck. It did when it was just threaded directly into the cast iron.

I used standard length helicoils and a drop of locktite when installing them.

I mounted them on the pillar drill table, ensured it was dead plum and by hand only threaded into the barrel just using the Chuck as a guide.
Posted By: chaterlea25 Re: Stretched head bolt - 02/03/21 10:04 pm
Hi All,
Helecoils come in 3 standard lengths , 1D 1.5D and 2D where D is the bolt diameter
Timesert solid inserts are the same outside diameter as helecoils

John
Posted By: Ignoramus Re: Stretched head bolt - 02/03/21 11:09 pm
Originally Posted by chaterlea25
Hi All,
Helecoils come in 3 standard lengths , 1D 1.5D and 2D where D is the bolt diameter
Timesert solid inserts are the same outside diameter as helecoils

John


There you go David P ........go with the 2D that would give you plenty of threads engaged

so 20tpi x .375 = 7.5 threads engaged , rule of thumb is MIN of 1.5 x nominal diameter but more is always better

check out the lengths u can get the "timesert" solid ones in , never heard of those i always just make my own like i said to mean to buy a kit for just one thread

I assume the "timesert " ones are hardened as the helicoils are ? .........

top info Chaterlea
Posted By: Fullminator Re: Stretched head bolt - 02/03/21 11:27 pm
David, I recommend British Tools & Fasteners.
https://britishfasteners.com/
They have most every size coil spring thread repair kit, British nuts, bolts, screws, taps & dies imaginable.
Fullminator.
Posted By: DavidP Re: Stretched head bolt - 02/04/21 5:39 am
I just looked and the Timeserts are only available in 3/8x16 or 24tpi. The solid insert seems to be more suited to high-torque applications, but the kit is at least $80.
I have found coil insert kits in 3/8" BSF for less than half that much. So far the only threads I've repaired on this bike is one rocker cover stud. I just used a UNC coil for this, I put the coil in with red Loctite.
Thanks for the clarification of the length specification, I'll look for at least 1.5D. In any case, the barrels must come off.
Posted By: DavidP Re: Stretched head bolt - 02/04/21 6:09 am
Actually, if the outside threads are the same, I could just buy some Timesert inserts and use the Helicoil tap which I already have for 3/8"x16? Just need to countersink the holes.
Just buy some grade 8 bolts. Don't know what that would do to the torque settings using a different thread pitch though.
Posted By: Allan G Re: Stretched head bolt - 02/04/21 11:49 am
Just buy some helicoils David and don't over complicate life. Im running 10:1 compression in my a65 and they have held up fine for about 4 years.

with helicoils your coming very close to the wall of the bore, espeically if your already running over sized pistons... Add the top hat of the timesert in there as well and you might be very close or broken into the cylinder wall. You might not be too bad if its the one behind the pushrod tunnel but your not really gaining anything. If it was a spark plug thread, I would say fit a timesert.... But it isn't.
Posted By: Ignoramus Re: Stretched head bolt - 02/04/21 5:22 pm
in any event get the longest ones you can ..........dont worry about different pitch and torque settings it wont make any practical difference , the amount of pull down will be the same regardless of pitch , they wont loosen of that's what spring washers are for , flat washer on alloy head spring washer under head of bolt
Posted By: Ola Re: Stretched head bolt - 02/04/21 6:45 pm
David - I have seen new (after market) head bolts that were very sloppy. I would try a known good bolt before going to any helicoiling.

Regards
Posted By: Ignoramus Re: Stretched head bolt - 02/04/21 7:00 pm
Originally Posted by Ola
David - I have seen new (after market) head bolts that were very sloppy. I would try a known good bolt before going to any helicoiling.

Regards

actually that is a really good comment ! i hadnt even though of the possibility that the aftermarket bolts could be undersize on the effective (pitch) diameter ....definitely try a known good one! and see if it is loose
Posted By: Allan G Re: Stretched head bolt - 02/04/21 10:01 pm
Might be worth adding to the good comments above that bsa increased the washer thickness to a shade under 3mm from the original 1.5mm. This was to address oil leaks.
Posted By: Mark Z Re: Stretched head bolt - 02/05/21 2:27 am
Originally Posted by Allan G
As mentioned earlier I helicoiled mine. Since doing that I haven’t suffered with any oil weeps from the head gasket after wringing its neck. It did when it was just threaded directly into the cast iron.

Allan, how did using heal-a-coils alleviate your leaking problem?
Posted By: DavidP Re: Stretched head bolt - 02/05/21 2:31 am
Originally Posted by Allan G
with helicoils your coming very close to the wall of the bore, espeically if your already running over sized pistons...
Thanks, I had not thought of that. I'm at +0.080, so that might be an issue.

Originally Posted by Ola
David - I have seen new (after market) head bolts that were very sloppy. I would try a known good bolt before going to any helicoiling.

Regards
50 year old engine from a company which went out of business 48 years ago makes it kind of difficult to find anything but after market bolts. The only other 3/8" BSF bolts I have are the old head bolts. The new ones came from Steadfast.

At this point my only other option is another set of cylinders. I have a set with one broken fin, which might be 20 over. However, they're early so I would need to resize and relocate the holes for the base studs. Add to that new pistons, rings and machine work.
Quite frankly the bike is not worth it to me to spend too much time and money on it.
Posted By: NickL Re: Stretched head bolt - 02/05/21 4:16 am
If you are going to replace and helicoil all 4 i would use 3/8 UNF as you can
buy either grade 8 or allen bolts (grade 12 or 14) easily.
The engine i did for the race bike i prepare had good threads so i just bought
grade 8 3/8 unf bolts which were plenty long enough then cut them and ran a
3/8 bsf thread on them. The heads are unf but they are good quality bolts and
that's what you are after. I too have come across crap bolts/studs.
If you are replacing the studs as well, use the 71/72 type they have much longer
threaded ends on the barrel and are shaped to bottom properly. The kits that are
sold now supply shorter studs like the earlier ones.
Just my 2c

30lbs is fine on them.
Posted By: Allan G Re: Stretched head bolt - 02/05/21 7:35 am
Originally Posted by Mark Z
Originally Posted by Allan G
As mentioned earlier I helicoiled mine. Since doing that I haven’t suffered with any oil weeps from the head gasket after wringing its neck. It did when it was just threaded directly into the cast iron.

Allan, how did using heal-a-coils alleviate your leaking problem?

The helicoils provided a decent thread for the bolts to lock in to.
Posted By: DavidP Re: Stretched head bolt - 02/16/21 5:02 am
I took a closer look at two of the old head bolts. One, which has the proper 3/8"W head, is marked Rubery Owen T55-65 on the head. After researching the company, I presume that this is OEM, as supplied to BSA.
The other has a 9/16" AF head. It has a raised place in the center with two ovate stampings which might have originally been numbers? It's the correct thread but a mystery as to who made it.
The new ones from Steadfast have no markings.
I got a Recoil kit in BSF. Got the cylinders waiting on my drill press. Must be careful to get the bit concentric with the original hole. It's a bit frigid in the shop these days.
Posted By: Mark Z Re: Stretched head bolt - 02/17/21 4:51 am
Right David, original bolts are Rubery Owen. The two marks on the other bolt may be just hash marks, as appear on much ordinary hardware.

Can you use the cylinder head to make a drilling template, to then bolt to the barrel? Just a thought...
Posted By: DavidP Re: Stretched head bolt - 02/17/21 6:22 am
Not hash marks, as on most American bolts. The only similar markings I can find in a search are numbers on certain metric bolts. I really wonder who would've made a bolt with British threads and unified heads? The first time I removed the head I didn't think twice about it, everybody "knows" that they went unified in '69. laughing
I'm not doing anything until it gets to at least 40 degrees in my shop. It's in the teens now.
Posted By: NickL Re: Stretched head bolt - 02/17/21 7:07 am
The head bolts never went unified on the a65's.
Chances are someone has just run a die down a cut off 3/8 unified bolt.
Or put it in a lathe and threaded it BSF.
Triumphs did not change for a while as well, use up existing stocks etc.

The OEM bolts are grade 8 that would mean 6 lines on the head in later terms
3 lines = grade 5.

https://www.fastenerdata.co.uk/fastener-grades#ugrade
Posted By: Ignoramus Re: Stretched head bolt - 02/18/21 2:24 am
Nick L recons :

buy either grade 8 or allen bolts (grade 12 or 14) easily

grade 12 cap screws are excellent material .........very high tensile , but still machine able / tap able , (just) best to power tap the sods though , probably 4140 grade .....i often buy a few realy long cap screws with a short thread as they are a very cost effective way of getting just a few inches of good grade material without having to go to a steel merchant who will want to sell you a 3.6 meter bar minimum!

if you get them with a unf thread, or even metric fine series and tap them to what ever size you need you have made a top of the line thread insert , retap the offending hole using a 2nd cut or taper tap and wind then in as hard as you can the hack them off with a hacksaw , file them flush and you have a forever repair ! done that countless times

oh and by the way .......when tapping high tensiles always go .0,1-.0.2 mm above the drilling size (much more on large diameters ) , depending on pitch and diameter , 80% thread is plenty on that stuff and you wont get so many busted taps
Posted By: DavidP Re: Stretched head bolt - 02/19/21 6:58 am
Recoil inserts are now installed with red Loctite to make sure they don't move.
Posted By: Allan G Re: Stretched head bolt - 02/19/21 7:37 am
Originally Posted by DavidP
Recoil inserts are now installed with red Loctite to make sure they don't move.

This is what I do. Just run a tap down them just to make sure none of the locktite has oozed through the wire and blocking the internally threaded area.
Posted By: Mitch Re: Stretched head bolt - 02/19/21 8:29 am
Helicoil has been used in Aircraft engines for at least 70 years or so (aircraft is my trade, for 40 years) they are used in some new construction and are approved as a repair in most situations. I've never seen a properly install Helicoil fail. Recoil appears to be the same. BUT, as noted, the length of the coil can be critical. for instance, BMW oilheads (and some airheads) have very high head bolt torques that are right on the verge of pulling threads in the aluminum. it's a common repair on those bikes. but it only works with the long coils, the standard short coils tend to pull out
Posted By: Richard Phillips Re: Stretched head bolt - 02/20/21 9:08 pm
I believe ARP makes a bolt kit for our engines. You have to go on their web sight to check it.

Yes helicoils. Use to machine electrical chassises for Raytheon. The main mounting holes where all helicoiled.
Posted By: DavidP Re: Stretched head bolt - 03/04/21 4:13 am
Well, the recoils are in place. The problem is that I can't thread the bolts in far enough. The coils which come with the kit are 1.5d (0.56"), but the head bolts need to thread in at least 3/4". They bind as soon as they get to the end of the coil (yes, I broke off the tangs.) A 3/8" BSF tap behaves the same way. Only thing I can think of at this point is to remove the two I've installed and either get some 2d coils, which are hard to find and cost almost as much as the whole kit. Or install new 1.5d coils about 1/4" below the top of the hole.
Posted By: NickL Re: Stretched head bolt - 03/04/21 5:32 am
I know you dislike me commenting but i think that either the helicoil tap
wasn't run down far enough and the coils are tapering in at the lower end
or there is some swarf etc or maybe broken threads in the holes.
The BSF tap should go down it's full length on the cylinder, a good inch or
more. Are you sure you were using a plug type tap?
I'm only trying to help btw, not have a pop at you.
Posted By: Allan G Re: Stretched head bolt - 03/04/21 8:10 am
Originally Posted by NickL
I know you dislike me commenting but i think that either the helicoil tap
wasn't run down far enough and the coils are tapering in at the lower end
or there is some swarf etc or maybe broken threads in the holes.
The BSF tap should go down it's full length on the cylinder, a good inch or
more. Are you sure you were using a plug type tap?
I'm only trying to help btw, not have a pop at you.

Plus 1, it sounds like the original threads were only cleared out deep enough to suit the helicoils. So your getting to the bottom the. Hitting another thread, maybe.

As per Nicks suggestion, take the coil out and thread the tap deeper, then reseat the coil. I like to set the coils just below the surface, never flush.
Posted By: chaterlea25 Re: Stretched head bolt - 03/04/21 10:36 pm
Hi All,
A problem I have come across when fitting some fine thread inserts is that when snapping off the tang the bottom coil jumps a thread
so preventing the bolt threading through the insert, This can be hard to see at times
If it happens I weaken the insert break off point some more and this sorts the issue

John
Posted By: DavidP Re: Stretched head bolt - 03/05/21 6:40 am
Good advice all. The bottom coil of the one which I managed to extract did appear to have been pushed away from the wall. I ran the tap further into the hole and will try again. The two coils I put in were recessed below the top by maybe an 1/8".
The real problem is that the drill bit starts chattering once it gets close to the bottom of the hole.
The only other coil on this engine is for one of the rocker cover studs, and that doesn't need to be so long.

Nick, I appreciate your comments and knowledge of these bikes. I'm just confused by your undying allegiance to this brand. I've had this bike since I joined this forum and I still don't see the attraction.
Posted By: Allan G Re: Stretched head bolt - 03/05/21 10:55 am
Originally Posted by DavidP
I've had this bike since I joined this forum and I still don't see the attraction.


you know what they say, get rid of the things that dont make you happy.
Posted By: DMadigan Re: Stretched head bolt - 03/05/21 4:14 pm
Maybe you should have used a solid insert.
Posted By: Allan G Re: Stretched head bolt - 03/05/21 9:18 pm
Originally Posted by DMadigan
Maybe you should have used a solid insert.

Nothing wrong with the helicoils, and if the thread wasn’t cleared deep enough for the bolt then the problem would still exist.
Posted By: DavidP Re: Stretched head bolt - 03/06/21 6:41 am
Originally Posted by DMadigan
Maybe you should have used a solid insert.
That was my first inclination, though they are not available in BSF. I could probably find a UNF bolt in 3 1/2" length too, just in case.
Originally Posted by Allan G
Originally Posted by DavidP
I've had this bike since I joined this forum and I still don't see the attraction.
you know what they say, get rid of the things that dont make you happy.
I'll try to, but I think a running bike might bring a bit more money. I need the space.
Posted By: DMadigan Re: Stretched head bolt - 03/06/21 3:28 pm
With a threaded tube you do not have the problem of the wire jumping when breaking off the tang.
What you probably know already, I would have made one. If a BSF insert tap was not available then thread the outside of the tube for a Heli-coil and the inside to 3/8" BSF.
Posted By: Mark Z Re: Stretched head bolt - 03/07/21 5:19 pm
David, forgive me if this is too obvious a question, but did you use a "bottom tap" (square on the end, not tapered)?

In the interest of a "quick and dirty" fix, for a bike that you plan to get rid of, how much of the bolt would you have to cut off to make it work? There's about an inch of thread, losing 1/8" or even 1/4" would not be disastrous, I think.
Posted By: DavidP Re: Stretched head bolt - 03/08/21 5:55 am
Originally Posted by Mark Z
David, forgive me if this is too obvious a question, but did you use a "bottom tap" (square on the end, not tapered)?
The tap which came with the Recoil kit is a bottom tap. The 3/8" BSF tap I have is tapered.
In any case, I have reinserted a new coil in the one hole after drilling and taping deeper. I worried the tang a bit with some long nosed tech pliers before breaking it off. The bolt gave a little resistance at the bottom of the coil but goes all the way in now.
I'll need to remove and redo one other coil and be more thorough when I drill and tap the other two holes. The threads in the center hole are still good.
What scared me the first time is that once the bit gets about 3/4" in it starts to chatter. I only have a bench-top drill press with C-clamps to hold the work in place.
Posted By: NickL Re: Stretched head bolt - 03/08/21 11:23 pm
Originally Posted by DavidP
Good advice all. The bottom coil of the one which I managed to extract did appear to have been pushed away from the wall. I ran the tap further into the hole and will try again. The two coils I put in were recessed below the top by maybe an 1/8".
The real problem is that the drill bit starts chattering once it gets close to the bottom of the hole.
The only other coil on this engine is for one of the rocker cover studs, and that doesn't need to be so long.

Nick, I appreciate your comments and knowledge of these bikes. I'm just confused by your undying allegiance to this brand. I've had this bike since I joined this forum and I still don't see the attraction.


Well David, i suppose it's just that the beezers seem to stand the thrashing and abuse that i give 'em
without all the fuss that triumphs seem to demand. I know they are not as pretty but i've owned both for
a long time and the maintenance on the triumph must amount to maybe 2 or 3 times the hours. Plus 2
or 3 times the vibes, rattles and oil leaks.
My t120 will go this year, i'll hang on to the t'bolt and maybe get a new enfield twin.
Posted By: DavidP Re: Stretched head bolt - 03/09/21 6:09 am
Nick, I've found it to be just the opposite, though I've only owned the one A65 and my first Triumph was a T150V.
I can set all six valves on my Trident in less time than it takes to remove the rocker cover from my OIF A65. And don't get me started on how much less trouble it is to get into the gearbox on a Triumph, or how much y'all spend to make the crank get enough oil.
There's good and bad in all of them. I always dreamed of designing an engine with the good ideas from all of them.
BTW: I haven't noticed much difference in the vibration between the two twins. I have noticed that the lamps don't last very long on the A65, Could be a balance issue, neither have been rebalanced since they left the factory and the A65 is +0.060. I really don't care for either one on the motorway.

In any case, two coils replaced and the bolts thread properly, two more to be installed.
Posted By: Ignoramus Re: Stretched head bolt - 03/10/21 9:35 pm
Ah Yes , the controversy between BSA and Triumph continues

For all their faults i recon the BSA's just plain look better ...IMO teh 70 A65L in USA trim was the best ever
Posted By: DavidP Re: Stretched head bolt - 03/11/21 6:27 am
Originally Posted by Ignoramus
For all their faults i recon the BSA's just plain look better ...IMO teh 70 A65L in USA trim was the best ever
I'll agree with that. Those chrome tanks are pretty. I particularly like the '72 R3.
And, though the '71 US tank looks a bit Japanese, especially with the original paint, the shape works better with the OIF side covers.
The '70 Bonneville is also considered by many to be the best ever.
Posted By: DavidP Re: Stretched head bolt - 03/14/21 5:10 am
Originally Posted by DMadigan
Maybe you should have used a solid insert.
That was one of my first questions. They are only available in Unified threads and I'd already spent good money on the BSF bolts.
In any case, all four Recoils are in place. The bolts thread all the way in. I only need to lightly hone the bores and wash up.
Posted By: Ignoramus Re: Stretched head bolt - 03/14/21 8:32 pm
Originally Posted by DavidP
Originally Posted by Ignoramus
For all their faults i recon the BSA's just plain look better ...IMO teh 70 A65L in USA trim was the best ever
I'll agree with that. Those chrome tanks are pretty. I particularly like the '72 R3.
And, though the '71 US tank looks a bit Japanese, especially with the original paint, the shape works better with the OIF side covers.
The '70 Bonneville is also considered by many to be the best ever.

yeah the OIF tank does look a bit ...........and as for the indictors ?

but ya know i will have to amend my remark about the us A65L being the best ...perhaps a very close second to the 68 Rocket 3 DANG i lusted after one of those in my youth ...would call in at the bike shop on Friday nights just to look at the red one they had ....budget just wouldn't make it however
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