Author Topic: Big end bolts  (Read 1754 times)

Offline RichardL

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Re: Big end bolts
« Reply #15 on: 23.11. 2015 01:40 »
Another issue came to light a couple of years ago the replacement  Triumph type nuts that were commonly sold were made of cheese !!!

 *lol*

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Offline Guy Wilson

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Re: Big end bolts
« Reply #16 on: 23.11. 2015 11:11 »
This the surviving big end on my small journal crank. The rods look tech same as yours Ivor, but not the nuts an bolts etc. 
I believe the nuts and castle bolts with the split pin to lock are  original factory fittings.
Guy

Offline Topdad

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Re: Big end bolts
« Reply #17 on: 23.11. 2015 13:49 »
I rebuilt a small journal motor S/W arm by fitting the internals of a plunger . They had the same nuts as those shown by Guy. never had any problems with the st up.
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Online KiwiGF

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Re: Big end bolts
« Reply #18 on: 23.11. 2015 19:17 »
Just for interest....as I have lightning engineering billet rods in my SJ engine and have dodged the question.

If new rod bolts are used with original rods, what determines the torque they should be done up to? Is the determined by the bolt supplier? Or by what BSA originally stated was the correct torque?

I'm thinking the rods may distort if bolts exert too much pressure on them.

Do new bolts like the ARP bolts have the same thread spec as the original bolts? As that could affect the torque setting..... *dunno*

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Online KiwiGF

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Re: Big end bolts
« Reply #19 on: 23.11. 2015 19:49 »
I did a search and this might answer my question above....

http://www.a7a10.net/forum/index.php?topic=4388.msg29989#msg29989
New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

1949 C11 rigid, but why!!! (cos it was cheap)

1937 B21, project missing parts, mission impossible?

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife

Online chaterlea25

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Re: Big end bolts
« Reply #20 on: 23.11. 2015 20:16 »
Hi Kiwi and All,
There was a discussion on the use of ARP bolts here on the forum some time ago and recommended torque's
and bolt stretch figures given.
The ARP bolts have UNF threads so the BSA torques do not apply
ARP send instructions with the bolts and special lube for the threads
Aftermarket rods that use ARP bolts require higher torques than on BSA rods

I fitted ARP bolts to the last A10 engine I built and followed the torque figures given, and the bolt stretch was correct.

Quote
I rebuilt a small journal motor S/W arm by fitting the internals of a plunger . They had the same nuts as those shown by Guy. never had any problems with the st up.

Topdad
How were you able to torque them? as there no room for a socket to fit in the photos shown ?
Did you get a full depth of thread on the nuts?
The nut has to go fully onto the bolt to get full strength and security

Cheers
John



1961 Super Rocket
1963 RGS (ongoing)

Online Brian

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Re: Big end bolts
« Reply #21 on: 24.11. 2015 01:50 »
Here's a pic of the ARP bolts. I contacted ARP's techinical department some time ago regarding the torque figures for them and when fitted to std BSA rods they recommended 28 ft/lbs.

I will only use these bolts these days, mainly because they are a "known factor". Genuine ones are not available and the rest are all of a unknown origin so not worth the risk.

Offline RichardL

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Re: Big end bolts
« Reply #22 on: 24.11. 2015 02:28 »
Brian,

Did they also tell you the dimensions for the stretched bolt when tightened?

Richard L.
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Online Brian

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Re: Big end bolts
« Reply #23 on: 24.11. 2015 02:36 »
I dont think so Richard but it was some years ago so they may have.

When I bought the bolts they came with a slip of paper recommending a very high torque figure, I cant remember exactly but it was 36 or 38 ft/lbs which i thought was way too high for a BSA rod so I contacted them and they recommended the 28 which is what I used and have used ever since.

Its worth the expense to put quality bolts in as if they fail it will cost a whole lot more, I think its called the big bang theory !

Offline Topdad

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Re: Big end bolts
« Reply #24 on: 24.11. 2015 10:43 »
Good morning John, there was no problem torqueing them ,as a complete novice to bike engine rebuilding (,this was my first shot at an A10 ) plus I was flying in the face of advice from supposedly wiser heads than mine ie you can't do that etc,  I took extra care even to the point of polishing everything and getting every thing absolutely spotlessly clean .The only problem I remember having was getting the correct new washers for the big end bolts so as the holes for the spit pins lined up when torqued ,I remember my Dad suggesting taking them slightly pas tthe hole then back slightly whilst my basic torque wrench was clicking .I was blessed with the best kit I could get and the socket fitted perfectly ,if you look at V8's nuts ( no pun intended  *whistle*) you'll see as you pointed out a real problem whilst the ones of Guys are well proud and can be tightened correctly, cheers bob
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Online chaterlea25

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Re: Big end bolts
« Reply #25 on: 24.11. 2015 18:31 »
Hi ALL,
Topdad,
Apologies I misread you r earlier post, mixing up V8 and guys pics in my head *red*
Yes it can pe problematic getting the pin holes to line up, sometimes you can over come this by swopping nuts around
On that point, were not the torque settings  for early engines less than later ones ???

Richard.
Quote
Did they also tell you the dimensions for the stretched bolt when tightened?

Yes, I got instructions with the bolts I bought, also instructions about cycling the bolt torques a couple of times ,
measure, tighten - measure stretch, loosen, measure again  !!
so the stretch is measured, and also that the bolt returns to its original length when loosened


Regards
John



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1963 RGS (ongoing)

Online bsa-bill

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Re: Big end bolts
« Reply #26 on: 24.11. 2015 18:59 »
Quote
about cycling the bolt torques a couple of times ,

similar instructions to those I got if memory serves I think torqued to 27 three times
All the best - Bill
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Online Greybeard

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Re: Big end bolts
« Reply #27 on: 24.11. 2015 19:48 »
I'm confused. If I use these super new Big End bolts can I torque them up or must I use the stretch technique?

Online chaterlea25

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Re: Big end bolts
« Reply #28 on: 24.11. 2015 22:23 »
Hi GB,
I found that the 28ft lbs on the ARP bolts on BSA rods (with their lube) gave the required "stretch"

HTH
John
1961 Super Rocket
1963 RGS (ongoing)

Offline RichardL

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Re: Big end bolts
« Reply #29 on: 24.11. 2015 23:57 »
I'm confused. If I use these super new Big End bolts can I torque them up or must I use the stretch technique?

Part of the instructions that are sent with the bolts is to keep a record of the original length of every bolt so that you know if it has gone out of spec (that is, experienced plastic deformation). As I recall, you don't own a 2" - 3" micrometer. Might not be a bad time to invest, but you shouldn't have to spend a lot, just be sure you get one that reads to 0.0001" precision. While you're at it, might as well get a 1" - 2" for those pesky journals. Otherwise, beer for your nearest friendly machine-shop owner.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.