Torque Talk

[Steve G]

I have sheared a couple of bolts. I am currently reinstalling my engine after replacing the gearbox shaft housing. Where torque figures are given I am using a torque wrench to torque the bolts. If the bolts look worn/rusty/stretched I am replacing them. I have not yet deliberately oiled any bolts but all are existing ones and so have trace oil on them even after a good wipe. I am applying a spot of Loctite Threadlocker near the end of the thread of each bolt, after finding that quite a few of the bolts after my last engine installation were fairly loose. I am not using Threadlocker where the bolt is fastened by a Nyloc nut. Where torque figures were not given specifically I was going by the general settings that refer to spanner sizes. The bolts in question were reused 5/16 thread diameter UNC 2" long engine mount bolts (on the spacered side). After one broke I knew I was going to buy four new ones so 'tested' with less torque, it too sheared. The bolts may well have failed because they were old but I could have over torqued them.

I did a search and found this very useful thread;
elan-f15/tightening-torque-values-t22069.html
But still have a few questions.

I would like to know if anyone has compiled a definitive list of all fastener torque settings for the Lotus Elan. If not then I would like to do it. By this I mean expanding upon and possibly altering the settings given in the Workshop Manual.

I would also like to learn what people's opinions are on where a torque wrench should be used and when 'feel' is preferable.

Then I think it would be worthwhile to discuss the use of Loctite threadlocker or equivalent and when and what type of lubricant should be used.

Thanks.

[billwill]

Apart from the cylinder head bolts and the cam-sprocket bolts, I don't think I ever use a torque wrench. I just do it by feel.

<later>

PS that excludes bolts inside the engine such as Con-rods & main bearings, I didn't mention those as I've hardly ever done major internal engine stuff.

[garyeanderson]

Check your torque wrench, 13 ft/lbs for the 5/16 unc bolts should not be a problem. I think your wrench has an issue. What spec were you using, no details mean asking these questions as I or anyone else has a clue. It broke, what happened? is not a question

more from the piss-ant

[Steve G]

I couldn't remember the torque settings, this is part of the problem and why I want an online list of torque settings. I refer to my iPhone docs and even this forum when working on the car. I've got a shiny new torque wrench (Teng Tools) with a calibration certificate. I think I may have used more than 13 ft lbs, are the general figures given the spanner size or the thread diameter? I think I looked up the spanner size for the 5/16 bolts so would have used the setting for a 5/8 or whatever the spanner size is. Oops...

[69S4]

Is this shiny new torque wrench a 1/2" size by any chance? For bolts that size I'd probably use a 3/8 size wrench as the torque required is more in the "linear" part of the scale. A 1/2" wrench is more likely to be untrustworthy right at the bottom of its scale. Actually, like BillWill I probably wouldn't use a torque wrench at all for bolts like that as I've snapped enough in my "career" to have a feel for when things are tightening correctly and I tend to trust that more than numbers on a scale. There are exceptions like head bolts etc but for most stuff I'll just use a ring spanner or a socket.

[garyeanderson]

here is the chart out of the 1970 workshop manual.

[CSICO]

Hi!
I have attached a couple of files and links which might be a little help for you.
To the subject: I think the opinion already stated that tightening bolts 'by feel' is absolutely correct, especially when it comes to parts where gaskets are involved like water pump etc. Of course, head gaskets are a different story. When training apprenticces how to get some feeling for tightening I simply put a nut in a vice, give them the mating bolt with a thick washer to make sure the head of the bolt is contacting the nut and not the end of the tread and let them tie the bolt until it 'dies'. This is repeated with bolts and nuts of different strength and dry and with lubrication on tread and head. So far the response has been good and the consumption of Heli Coils has dropped as well... Just an idea, but I rather wreck some cheap parts before start repairing treads in cylinder blocks. Torque wrenches: the rule is actually quite simple as already stated: if you have a bolt which needs tightening with 30NM / 22lb/ft you chose the wrench witch has, lets say a range of 5NM - 100NM / 5lb/ft - 75lb/ft and not the one which starts at 25 Nm / 20lb/ft and ends by 200NM / 150lb/ft. Having learnt it the hard way: be careful with testing certificates, read the small print. A good, average torque wrench has a tolerance of +/- 4%; the one to look for is in the range of +/- 2% (probably not the cheapest one). The thing needs regular checking, ISO 9000 says at least every two years in a normal workshop environment, often is replacement cheaper then adjusting. A good thing to look at is the ARP Site how they recommend to set important bolts like con rod bolts and so on. I tighten these bolts the way ARP recommends (made the tool by myself) and never had any problems.
Let me know how you are getting on with your project and glad to help if you have any questions!
Cheers
Csico

- oouu- some of the links are in german, I hope this causes not to much of a problem!?!

http://www.britishfasteners.com/index.php
http://www.arp-bolts.com/pages/technical.shtml
http://www.pfeffer.ch/gewinde.htm
http://www.gewinde-normen.de/

[Steve G]

here is the chart out of the 1970 workshop manual.

That's the one I used, I went by 1/2 UNC for the engine mount bolts as that was the spanner size (they are 5/16 thread diameter). I think I know the problem now, can someone just confirm that the sizes given on the attached chart are thread diameter and not spanner size?

Thanks for all you advice so far guys. Very useful info on using 'feel'. This is what I have always done and I guess this is something I will have to learn with a bit more accuracy.

This is my torque wrench, it's nothing special but I did think at the time that it was a quality item. It says +/-4%. http://www.teng.co.uk/1292ag-ep-teng-to ... 485_pd.asp

It starts at 30 lb ft so probably no good for most applications anyway, certainly nothing below 7/16 UNC.

Does anyone have any thoughts about lubrication and Threadlocker? Is a bit of engine oil OK for lubricating bolts? Should all bolts be lubricated? Should I always use Threadlocker?

[garyeanderson]

Ask yourself one question.

Did I used the 1/2 inch unc or 1/2 unf wrench?

Gary

the chart is for the bolt shank, not the bolt head size.

[Elan45]

Steve,

You don't mention where you live and that may have some bearing on what you've done and what is to come. I have to admit, a huge reason for your failure is your mis-use of the torque spec chart, by using 1/2 settings for a 5/16 bolt. You will also note on on your torque chart, that there will be different settings for different grades of bolts. You didn't mention any markings on the heads of the bolts.

In the UK, bolts had designations of R, S or T. In the US, Grade 2 head is un-marked, grade 5 has three lines, one from every other point of the hex to the center, grade 8 has 6 lines, one from each point to tthse center. The torque settings are very different. Don't use unmarked bolts on anything important. On an Elan, that's everything. I use grade 5 for almost everything. They are plenty strong. On my Lotus 20/22 vintage racer, I use AN bolts with proper grip length. AN bolts are a little stronger than grade 5, but not as brittle as grade 8. Many engine bolts are special for their applications. Examples are head bolts, rod bolts and flywheel bolts. I use only original replacements, ARP or other performance replacements where appropriate.

Roger

[Steve G]

Thanks, I'm in the UK. I have bought Grade S zinc anodised replacements for the bolts and it's worth mentioning that the only bolts I have torqued from the general sizes were the ones that have sheared. All other bolts were torqued according to their setting given specifically in the Workshop manual, i.e. Bellhousing to Gearbox. When I rebuilt the engine I ordered ARP head bolts.

[collins_dan]

Steve, I would have made the same mistake. I found this chart which shows what head size and corresponding thread size.

http://www.boltdepot.com/fastener-infor ... -Size.aspx

Dan

[CSICO]

Does anyone have any thoughts about lubrication and Threadlocker? Is a bit of engine oil OK for lubricating bolts? Should all bolts be lubricated? Should I always use Threadlocker?[/quote]

Hi!
Your questions can't be answered with yes or now, it depends on several factors i.e. material, how often has the bolt to come off, where is it (a bolt fitted somewhere in the interior of the car smearing full with oil or grease is maybe not the best idea..) etc. Common sense helps here. Also, you asked basically two different questions:

lubrication of bolts/threads: preservation, makes it easier to come off again, torque issues
threadlocker: securing bolts/threads, ev. sealing of threads

Threadlocker: opinions differ, one basic thought: when this cars have been constructed and build for the first time there haven't been a lot -if- of this chemical stuff around. So, why use it now? It really depends how secure the bolt/nut has to be. I know people which 'glue' half of the car together, others use none. There are several methods for securing bolts, basically mechanical means (spring washers, twisted wire, metal flaps?, stretch bolts, welding, torque, etc) and chemical means (thread lockers with various strengths).

No-go's for chemical thread lockers is in general anything which has frequently to come of and a replacement of the bolt/nut is not planned/possible etc, i.e. wheel nuts and bolts.
Using this chemical stuff in alloy is also a bad idea, often the thread in the alloy gets damaged when loosening the bolt again. As soon you have to work with torque values which have to be exact, i.e con rods, that stuff is a bad idea as well because its lubrication abilities aren't that good. Apart from that, depending on the type/brand the leftovers can become quite hard, sometimes like glass and I don't like the idea that these bits are wandering through my newly build engine/gearbox. What you have to look for if you work with this lockers is: expiry date (believe it or not, they have one) normally the last for about two years; grade: in general are 3 grades existing: low, middle and heavy/strong. Bolts/nuts secured with low/middle grade products can normally be opened with 'normal' tools, for bolts/nuts treated with the strong kind often special tools and/or other procedures (i.e. heating) is required for loosening them. So again, read the small print. What is a absolute necissity when using chemical lockers is cleanliness. Any oil/grease/dirt leftovers have a direct impact of the 'performance'. Often to much is used as well, one or two drops are enough.

I think this are some of the more important points; other people have probably other opinions and knowledge.

Cheers!
Csico

[garyeanderson]

If you want some info to read, take a look at the ARP web page

http://arp-bolts.com/pages/faq.shtml

http://arp-bolts.com/pages/technical_torque_us.shtml

These two will get you started, while not a direct replacement for Twin Cam and Elan, one can look, read, and get a general idea of what is recommended by the manufacture of some pretty nice fasteners.

There are part numbers listed for twin cam stuff on this forum in the vender's area of this forum. It is not a direct list, you will need to know what you are looking for as there are other engine bolts listed. I guess if don't know then you will need to read up on stuff.

business-listings-f3/aptfast-carries-arp-fasteners-parts-numbers-for-twin-cam-t21062.html

Gary

[Esprit2]

The torque spec is given for the THREAD size, not the hex head size. If you use the torque stated for the hex head size, you will over-torque the fastener. (Whitworth is weird, and I don't know what to say about torque for those threads... ie, Whitworth sizes are head sizes).

Generic torque values in charts are given for clean, dry threads, unless otherwise stated. The charted torque values given in Lotus manuals, including the copy posted above, follow that statement.

The exception is certain critical engine fasteners that are simply understood "by those in the trade" to be torqued with oiled threads... like head, rod and main bearing bolts/ nuts. But those torque values are specifically called out for each application, and not something you just pick off a generic chart. Read and follow the assembly instructions.

Unfortunately, Lotus manuals are not good about giving specific torque conditions in the assembly instructions. It's as if the manuals presume the work is being done by a trained Lotus technician who knows what he's doing, and are written more like an overview as a reminder. They're not written in great step-by-step detail for an amateur mechanic, like a Haynes or Chilton's might be.

The generic torque in a chart also presumes similar materials. If a spec is stated for a Grade 8 bolt, that means clean and dry into a grade 8 nut. If you use the Grade 8 torque with a Grade 2 nut, you'll strip the nut's threads. Same with the Grade 8 bolt into an aluminum housing. For an application like a bolt into the engine block or head, Lotus will call out a specific torque for the application... not one from the generic chart. In that case, use the fasteners they call for, and the spec torque.

By the time the specifics applications are done, and assembly gets down to "All other nuts and bolts", refer to the chart, and presume clean, dry threads.

Anything you put on the threads (mineral oil, synthetic oil, Anti-Seize, Loctite, etc) reduces the friction involved in turning the fastener. Since each material that might be applied to the threads has a different degree of impact on friction, and since the writer of a generic torque spec for a standard thread size has no real control over what substance might be applied, the default is to simply not allow for anything to be applied. That covers all the generic bases equally. The spec is stated for clean, dry threads, unless otherwise stated.

Putting goop of some sort on a thread that should be clean and dry will result in the fastener being over-torqued. Very possibly to the point of failure.

Regards,
Tim Engel