Re-torque of cylinder head nuts...

[Antietam Classic Cycle]

I have a silly question.

Do I need to slacken the exhaust header from the head when re-torquing?

No.

[Phang]

No.

Thanks Charlie 

[Scud]

FYI - I recently retorqued the heads on my '03 V11 LeMans. I loosened all the nuts at the same time, then retorqued them all in stages (increasing torque until final number reached). However, I ended up with a small oil leak at the head (which was not there before).

I've recently been thinking that my problem could be that my torque wrench was not calibrated (I hadn't used it for probably 10 years). It is also a monster of a torque-wrench, going up to 200 ft-lbs. So - just a word of caution, make sure your torque wrench is calibrated (if it's a clicker-type). Also, as I understand it, clicker-type torque-wrenches are most accurate when reading near the middle of their ranges.

I bought a new, smaller wrench and am going to give that a try soon.

[Phang]

the 29~32lb/ft (39~44Nm) fall right in the middle of the embarrassing overlapping high/low zone of my two torque wrenches

the 3/8" drive range is 7.5lb/ft to 36.9lb/ft (10Nm to 50Nm)

the 1/2" drive range is 29.5lb/ft to 147.5lb/ft (40Nm to 200Nm)

Which one will you pick to do the job? (ignore the digital one)

[sidecarnutz]

To you folks who say "I don't see why you need to re-torque them"......

Ever own a ten year old Cali II and see the head weeping oil? Then you check the head torques and find they are all loose. I find it's a good idea to re-torque the heads every five years or so why doing your regular valve checks. Just good preventive maintenance.

I re-torqued the heads on my 25 year old Cali III recently. No weeps on it. Gotta love these old bikes.

I do it to new bikes as well during the break in service. The multiple heat cycles does make them settle in.

[Triple Jim]

FYI - I recently retorqued the heads on my '03 V11 LeMans. I loosened all the nuts at the same time, then retorqued them all in stages (increasing torque until final number reached). However, I ended up with a small oil leak at the head (which was not there before).

When you loosened them all at  once, the seal was likely broken.  I don't know why it didn't reseal when you tightened things up again, but the procedure I follow is to loosen one at a time, retorque that one, and go on the the next one, following the recommended pattern.

[Antietam Classic Cycle]

the 29~32lb/ft (39~44Nm) fall right in the middle of the embarrassing overlapping high/low zone of my two torque wrenches

the 3/8" drive range is 7.5lb/ft to 36.9lb/ft (10Nm to 50Nm)

the 1/2" drive range is 29.5lb/ft to 147.5lb/ft (40Nm to 200Nm)

Which one will you pick to do the job? (ignore the digital one)

I'd use the 1/2" drive and torque to 32 ft. lbs.

[normzone]

" Do I need to slacken the exhaust header from the head when re-torquing? "

Yes, and be certain that the bike is within +/- 250 foot of sea level.

[Kentktk]

Make sure to to find what the atmospheric pressure was at time of assembly and then adjust for the variance in pressure at the time you re-torque. Also if you lubricate the threads with oil check the viscosity at the temperature of initial assembly and then adjust for current ambient temperature.

[Kiwi_Roy]

You don't need a torque wrench, just tighten them till they strip then slacken off a tad.

[normzone]

" Also if you lubricate the threads with oil check the viscosity at the temperature of initial assembly and then adjust for current ambient temperature. "

That is only necessary if you do not use the correct kind of oil.

Castrol 70 weight requires you to torque slower but you don't need to check the viscosity.

[Mike Tashjian]

Torque wrench accuracy is usually measured at maximum rating and varies.  I see many at plus or minus 3 percent at maximum rated torque.  So try to use an appropriate size if possible. Pay attention on how your fasteners are suppose to be torqued.  Many say dry threads only and that means no oil for best accuracy. Oiled threads usually require much less torque.  If you have to change from what is recommended use common sense. As we hear Professionals give advise remember that amateurs may not have the same tools or skills to use them.  If unsure ask more questions or read your service manual which usually points you in the right direction.  Mike 

[Tom]

Some good advice.  A mini-workshop by computer.  Good for review.

[dxhall]

If the specs don't say anything about oiling the threads, the torque figure given is presumed to be for dry threads.

Keep in mind that torque is a derivative measurement.  The measurement you really need to ensure proper clamping force is the stretch of the bolt.  That's why manufacturers like Carrillo give stretch numbers for their rod bolts.

I once set up a connecting rod in a vise and measured the torque required to bring the rod bolt to the stretch number with the threads dry, lubed with oil, and lubed with moly.  There is a BIG difference.  If you oil a bolt and then torque it to the dry torque spec, you are certain to overtorque the bolt.

[Kentktk]

" Also if you lubricate the threads with oil check the viscosity at the temperature of initial assembly and then adjust for current ambient temperature. "

That is only necessary if you do not use the correct kind of oil.

Castrol 70 weight requires you to torque slower but you don't need to check the viscosity.

Thanks great info! You think even with a colder ambient than San Diego the slower torque will be self evident because of the slightly higher drag whilst turning or should I time initial contact of nut to head and adjust accordingly?

[Phang]

I'd use the 1/2" drive and torque to 32 ft. lbs.

Thanks for the advice Charlie 

[Phang]

" Do I need to slacken the exhaust header from the head when re-torquing? "

Yes, and be certain that the bike is within +/- 250 foot of sea level.

Will keep that in mind, thanks 

[redrider90]

What I have never understood, why is the Guzzi engine so different from other engines that it the heads have to be re-torqued for the life of the engine.
Anybody want to explain why? I have been doing it but I always wondered if this was something from the land of folklore.
So Rocker has piped in why and Triple Jim gives a reasonable explanation as to why one does not have to re-torque forever. Did I get your drift correct Jim?  Heck my if valve clearances stay stable does that indicates why bother with the heads??

[lucky phil]

If the specs don't say anything about oiling the threads, the torque figure given is presumed to be for dry threads.

Keep in mind that torque is a derivative measurement.  The measurement you really need to ensure proper clamping force is the stretch of the bolt.  That's why manufacturers like Carrillo give stretch numbers for their rod bolts.

I once set up a connecting rod in a vise and measured the torque required to bring the rod bolt to the stretch number with the threads dry, lubed with oil, and lubed with moly.  There is a BIG difference.  If you oil a bolt and then torque it to the dry torque spec, you are certain to overtorque the bolt.

And that's why torquing is the second least accurate method of tensioning a fastener.The least being using nothing at all.
It's also why most critical fasteners on production engines and chassis (head and rod bolts for example) these days are angle torqued. Takes the lube out of the equation by and large. Also the most accurate method when you can't measure stretch due to the fastener being in a blind hole.
Lots of fasteners are torque to yield as well these days, Chev head bolts as an example. The fastener is stretched until it yields on instillation thus causing it to work harden and give greater strength.Can't be reused once installed.
Ciao

[rbm]

Bolt Tension Errors Associated with a Torque Wrench article.