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Lister JK/JP big end bolts


flatplane8

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Hi,

 

Finally getting around to putting the pistons back in the JK4 engine I have. Todays question is about the castled nuts on the big end bolts. I've tightened them to 65lb ft (as per the manual) but none of the holes line up for the split pins. What do others do here? Should I keep tightening until they do, or use washers, or not use the pins but use locktite? They are fairly close, but it will take quite a bit more effort to turn those last few degrees.

 

Thanks,

 

Simon

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Rather than over tightening it would be safer if you back them off and then take them up again to align the holes even if it means some being a touch under 65lb ft. You could of course rub the nuts on a sheet of emery to get the extra bit.

Edited by bizzard
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Thanks, the holes line up at 25ft/lbs, so far too low I think.

To be honest if the big end studs and nuts are old or original I'd reduce the torque setting to 60 lb ft. Or I'd grind a touch off the base of the nuts by rubbing them on emery sheet on a mirror, it won't take much rubbing to get the pin slots to align up. Hold the nuts firm and steady whilst rubbing them, don't let them rock or you'll put a curve on them.

Oh yes. And every few rubs turn the nut a 1/4 turn, to keep it square.

Edited by bizzard
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Thanks Bizzard, I've been looking on the internet and have found people championing every one of these suggestions, and also those saying just tighten to torque spec and that's it. They are the original bolts and I think over tightening them is probably a bad idea as it will take quite a bit more torque to get the slots to line up over the holes. So I guess its either grind a touch off the nuts, use locktite or just leave them be.

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Thanks Bizzard, I've been looking on the internet and have found people championing every one of these suggestions, and also those saying just tighten to torque spec and that's it. They are the original bolts and I think over tightening them is probably a bad idea as it will take quite a bit more torque to get the slots to line up over the holes. So I guess its either grind a touch off the nuts, use locktite or just leave them be.

Self locking nuts would be better than Locktite, heat might break it down. I wouldn't use washers either which introduce a bit of give plus an extra slip surface. Grind yer nuts and use pins, I'd say.

Edited by bizzard
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Hi,

 

Finally getting around to putting the pistons back in the JK4 engine I have. Todays question is about the castled nuts on the big end bolts. I've tightened them to 65lb ft (as per the manual) but none of the holes line up for the split pins. What do others do here? Should I keep tightening until they do, or use washers, or not use the pins but use locktite? They are fairly close, but it will take quite a bit more effort to turn those last few degrees.

 

Thanks,

 

Simon

 

Can you move the nuts around and get as close as possible.

 

I note bizzard's concern over the age of these studs but in most environments a small controlled element of stretching is allowed. Most steel alloys tensile strength increases before yield and so normally you would tighten up to the next place where pins and holes align.

 

For tapered bearings you undo as overtightened bearings don't last long.

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Hi,

 

All the nuts are stamped with the rod number and the bolt that they correspond to, not sure why. I've kept them in the same order so would be reluctant to move them around. they may have been stamped after installation, as the 'flat' with the numbers stamped is the one that needs to move about 10 degrees to line up the hole. For now I'll continue with tightening them to 65ft/lbs and decide later whether to do anything else. As I read elsewhere on the internet a split pin won't hold a nut to a specified torque, rather it will stop it winding off (i.e. it could still move enough to reduce clamping force).

 

Thanks for all the replies so far! :)

 

Simon

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Ten degrees? Are you sure your torque wrench is accurate and not under tightening?

Richard

I'm guessing, it's a fraction of a turn. I've got two torque wrenches and they produce the same result. I tried another 5ftlbs and it barely moves, so to rotate that last bit will take quite a bit of force, hence my question.

 

Thanks,

 

Simon

Edited by flatplane8
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How about using a Swiss file to slightly reduce the appropriate flats on the castellated end of the nut? I'm sure the bloke who did mine just backed off to allow the pin to go in, I hope that's correct otherwise I might need to revisit them..

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How about using a Swiss file to slightly reduce the appropriate flats on the castellated end of the nut? I'm sure the bloke who did mine just backed off to allow the pin to go in, I hope that's correct otherwise I might need to revisit them..

That's another idea to consider, perhaps a bit better than grinding small amounts of the face of the nut as the castellated part isn't providing the clamping force, so any metal removed there won't be a problem.

 

I suppose the other thing I could do if part of the hole is exposed is use safety wire instead of split pins.

 

I realise I may well be worrying about something that isn't worth worrying about, but its good to find out what others are doing. :)

Edited by flatplane8
  • Greenie 1
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To be able to file accurately is a skill. Safer and easier to rub it on emery cloth. To reach the pin holes they would only need about 1 or maybe 2 thou rubbing off, a minute or two's work on each.

Edited by bizzard
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  • 2 weeks later...

Hi,

 

All the nuts are stamped with the rod number and the bolt that they correspond to, not sure why. I've kept them in the same order so would be reluctant to move them around. they may have been stamped after installation, as the 'flat' with the numbers stamped is the one that needs to move about 10 degrees to line up the hole. For now I'll continue with tightening them to 65ft/lbs and decide later whether to do anything else. As I read elsewhere on the internet a split pin won't hold a nut to a specified torque, rather it will stop it winding off (i.e. it could still move enough to reduce clamping force).

 

Thanks for all the replies so far! smile.png

 

Simon

The other thing to keep in mind is that most versions of the manuals for these dont even state torques. with them having been just done up F T or FT by the person assembling, therefore if your having issues with the pins lining up I would be inclined that if the torque required to line them up is within say + or - 3% ish that would be fine. As you can be certain that will still be closer than many of them ever would have been when new.

 

typo correction

Edited by martyn 1
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The other thing to keep in mind is that most versions of the manuals for these dont even state torques. with them having been just done up F of FT by the person assembling, therefore if your having issues with the pins lining up I would be inclined that if the torque required to line them up is within say + or - 3% ish that would be fine. As you can be certain that will still be closer than many of them ever would have been when new.

Could I ask what f of ft means? Its not a term I'm familiar with. The mechanic that did mine did mention about there being no definitive torque settings.

Cheers

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And FT is normally calibrated in units of white knuckle as in "Tight? It was F four white knuckles Tight".

 

Scale runs from 0 to 8 but may be modified and intensified by the addition of a sliding scaffold pole vernier.

 

N

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To be able to file accurately is a skill. Safer and easier to rub it on emery cloth. To reach the pin holes they would only need about 1 or maybe 2 thou rubbing off, a minute or two's work on each.

 

I second that.

 

I would place emery cloth or other fine abrasive paper on something very flat like glass and rub the nut along the paper.

 

The only issue is that abrasive material may be carried on the nut and so need a good clean before reassembly.

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Is that definitely the right torque setting?

All the engines I've built (Armstrong Siddeley star sapphire, rover p6, and bmc 1.5) the main bearing bolts have been around 65lbft and the big ends more like 35lbft.

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I would like to know the thread details before passing judgement.

 

65 ftlbs does seem high, I also concur with the values quoted for the BMC but I suspect they are smaller bolts?

 

I am left wondering if the bolts have stretched though temperature cycling and use and were found in the 25ft-lb position. Perhaps new ones might line up better?

 

I've never seen wired big end bolts and all b/e bolts I've come across normally stay in place through stiction.

 

If you want positive retainment for the existing studs feel there are two choices, one to tighten a part turn further for holes to line up, another to use thread-lock.

 

There are many instances where bolts are intentional placed into their 'plastic' limit where the last tightening is through some fraction of a turn. They are then marked as they can only be used a finite number of times, or simply discarded for new.

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Not the clearest picture, but shows the four castellated big end bolts. I'd still be tempted to reduce the castellated bit as precision isn't really an issue ar that end of the nut.

Martyn and steamraiser do a lot more of these, I suspect their advice is definitive.

post-23974-0-05359700-1485415259_thumb.jpg

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