Words of wisdom, checking head torque on Mark III engine

I have the following: A Mark III Commando that was rebuilt 300 miles back (and engine is NOT leaking) two torque wrenches, (one older Craftsman with pointer and chart, one new Pittsburgh Pro, bought in parking lot sale for $11.95 that clicks) a set of Whitworth sockets, and coffee. I have looked up torque settings and found a diagram with the order in which to check bolts. Any other Words of Wisdom?

Motion Pro torque wrench adapter tool allows you to access the underside bolts better. Uses regular wrenches. Torque wrench won't fit.

nortonmargie said:

have looked up torque settings and found a diagram with the order in which to check bolts. Any other Words of Wisdom?

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Five are "bolts". The others are 1/4"W hexagon nuts except for the two sleeve nuts (7 & 8) under the exhaust ports that have the later reduced 7/16" A/F hexagons. 3/16"W can be used but is a slacker fit. Fastener 2 usually requires a thinned-down spanner.



Fasteners 1, 9 & 10 need a slim (3/8" square drive) socket and extension.


I can reach bolt No.1 without having to unbolt the head steady, coils, etc. if I use a 75mm 3/8" square drive wobble extension.

I always find it a bit nerve racking checking the torque. But it is necessary. When I last did the engine on my bike some of the bolts/ nuts were very low.

I guess you know you crack then slightly undone before retorqing. That breaks the static friction. There are lots of differing opinions about whether the fasteners should be lubed etc before torquing. For what it's worth I just make sure they are clean but don't lube them. Very happy to defer to more knowledgeable persons.

baldy said:

Motion Pro torque wrench adapter tool allows you to access the underside bolts better. Uses regular wrenches. Torque wrench won't fit.

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Yup, it is a great tool if you do not have the nerve to "free-hand" torque the three underside nuts not reachable by a socket torque wrench directly. Comnoz has video's showing how easy it is to strip those head studs at not much over the spec'd torque.






Haven't tried it but one of these should work as well:

Tornado said:

Yup, it is a great tool if you do not have the nerve to "free-hand" torque the three underside nuts not reachable by a socket torque wrench directly. Comnoz has video's showing how easy it is to strip those head studs at not much over the spec'd torque.


View attachment 100752

Adjustable Torque Wrench Adapter, 08-0380 - Motion Pro

Motion Pro - High quality cables, tools and controls for motorcycles, ATVs, snowmobiles and personal watercraft.

www.motionpro.com

Haven't tried it but one of these should work as well:

Proto 3/8in Drive Torque Adapter 7/16in

Proto 3/8in Drive Torque Adapter 7/16in - J5114

www.acmetools.com

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Yes it works great!

Well, I don't have any of those special tools, but I do have an assortment of socket wrench extenders and small fingers. I'm going to try it Saturday. Wish me luck

johnm said:

I always find it a bit nerve racking checking the torque. But it is necessary. When I last did the engine on my bike some of the bolts/ nuts were very low.

I guess you know you crack then slightly undone before retorqing. That breaks the static friction. There are lots of differing opinions about whether the fasteners should be lubed etc before torquing. For what it's worth I just make sure they are clean but don't lube them. Very happy to defer to more knowledgeable persons.

Click to expand...

How do you know if the bolts/nuts are low a priori (that is beforehand) if you crack them first? You do not know, but if you slowly apply torque and the bolt/nut yields or moves before reaching specified torque, then you know it was low. If the bolt/nut does NOT move, you do not know if it is at spec or simply friction stuck. Then, I crack them, and reapply torque up to specification.

Applying lube to a bolt/nut greatly reduces friction and will upset the published torque limits, resulting in an over-torqued fastener at best, or a stripped out one at worst. As johnm recommends, just clean bolts/nuts but use no lube.

FWIW ..... head gaskets can yield (settle in) with time alone, without heat cycling. I torqued the head on my Atlas to specification, then diverted my attention to other issues. Months passed without cranking up. I then decided to check all fasteners on the head and found most to be low. How did I know them to be low? They moved (therefore not friction stuck) before my torque wrench reached specification. For those few which did not move, I noted the angle of my torque wrench at specified torque, cracked the fastener, then brought the fastener back to specification and noted again the angle of the wrench. If that angle was judged to be the same, then I concluded the fastener was at specified torque and not simply friction stuck.

FWIW II ..... you can easily make a torque wrench adapter by welding a nut on a spanner. Use a socket on the welded-on nut, then apply the spanner at right angles with no correction factor, or calculate the correction as Tornado's chart above shows.

Slick

"you can easily make a torque wrench adapter by welding a nut on a spanner"

That is, if you know how to weld and have welding equipment.

texasSlick said:

How do you know if the bolts/nuts are low a priori (that is beforehand) if you crack them first? You do not know, but if you slowly apply torque and the bolt/nut yields or moves before reaching specified torque, then you know it was low. If the bolt/nut does NOT move, you do not know if it is at spec or simply friction stuck. Then, I crack them, and reapply torque up to specification.

Applying lube to a bolt/nut greatly reduces friction and will upset the published torque limits, resulting in an over-torqued fastener at best, or a stripped out one at worst. As johnm recommends, just clean bolts/nuts but use no lube.

FWIW ..... head gaskets can yield with time alone, without heat cycling. I torqued the head on my Atlas to specification, then diverted my attention to other issues. Months passed without cranking up. I then decided to check all fasteners on the head and found most to be low. How did I know them to be low? They moved (therefore not friction stuck) before my torque wrench reached specification. For those few which did not move, I noted the angle of my torque wrench at specified torque, cracked the fastener, then brought the fastener back to specification and noted again the angle of the wrench. If that angle was judged to be the same, then I concluded the fastener was at specified torque and not simply friction stuck.

FWIW II ..... you can easily make a torque wrench adapter by welding a nut on a spanner. Use a socket on the welded-on nut, then apply the spanner at right angles with no correction factor, or calculate the correction as Tornado's chart above shows.

Slick

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How do you know if the bolts/nuts are low a priori (that is beforehand) if you crack them first?

In this case some were so low that they cracked with basically no torque at all. Surprisingly loose. But the method you describe makes sense and is a good idea.

nortonmargie said:

Well, I don't have any of those special tools, but I do have an assortment of socket wrench extenders and small fingers. I'm going to try it Saturday. Wish me luck

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I think you will find the two lower front "sleeve' nuts impossible to fit a socket wrench directly. Likely true for the rear underside nut as well. Those are the three at risk of pulling stud out of the soft alloy head when trying to use a hand spanner/wrench. The other upper side nuts or bolts thread into the iron block, not the alloy head.
Comnoz's testing videos show the three head stud pulling out with something like 35-40 ft-lbs (30 is spec).
Hence not worth the risk for the cost of the adaptor tool IMHO.

I did the awkward underneath the head nuts with the arrangement below...and FWIW if the adapter is at 90 degrees to the torque wrench as shown no correction is required.
I do realize the setup is less than ideal but it did the job using tools I already had on hand.

Just 4 inputs from me FWIW:

1. Torque wrenches aren’t magic, they’re just wrenches. There is a reason why the expensive ones are expensive. I wouldn’t have too much faith in the accuracy of your $11.95 wrench.
2. If you learn to get a ‘feel’ for tightness, your wrist can be more accurate than a torque wrench in difficult to access situations.
3. If you have a composite head gasket, you need to do this very regularly until things settle down, it could take 6-700 miles or more.
4. If the fasteners moved much, don’t forget to check the tappet clearances.

All torque wrenchs should be checked for accuracy. Here is an easy procedure for checking and adjusting:

Thanks to Bluto for showing me a setup I can do with tools on hand. I am planning to take the bike on a fairly lengthy ride and Motion Pro will not ship before then.
I believe the 1980 vintage Craftsman torque wrench is accurate. I plan to check accessible bolts with both wrenches and see if there is a disparity between readings.

A combination wrench and a fishing scale will work for the hard to access nuts if you have some rudimentary math skills.

Divide the length of the wrench by 12 and divide the required torque value by the resulting factor. That will give you the value that you need on the scale to achieve the torque spec.

Dan1950 said:

A combination wrench and a fishing scale will work for the hard to access nuts if you have some rudimentary math skills.

Divide the length of the wrench by 12 and divide the required torque value by the resulting factor. That will give you the value that you need on the scale to achieve the torque spec.

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But all fishermen are liars , their scales and measuring tapes are wishful sided. From a fisherman.

I never use a torque wrench on a cylinder head

baz said:

I never use a torque wrench on a cylinder head

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Yeah , me too. 4 Nortons later and never stripped anything. Ever. Plus never had a head gasket failure , ever. Go by feel young Luke. Feel the force.

baz said:

I never use a torque wrench on a cylinder head

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A motor machinist i know with a crook elbow said he has a built in torque wrench as his elbow clicks when he is tightening a motor down and he reckons thats how he gets his feel ..