Re-torque of cylinder head nuts...

[Stevex]

...on a 1980 LM2.
Is it best to slacken all nuts off then re-torque, or just re-torque as they are.
I've ridden about 400-500 miles since my initial rebuild and noticed signs of a slight oil weep around the base gasket of one cylinder.

[Vasco DG]

Crack 'em all off and re tighten 'em. Make sure threads are lubed.

Pete

[Perazzimx14]

1. Torque at rebuild
2. Let sit 24 hours. Loosen and re-torque
3. After a couple of heat cycles loosen and re-torque
4. Ride the guts out of it

[mtiberio]

I do one nut at a time, loosen it and torque, use criss cross

[grebmrof]

I do one nut at a time, loosen it and torque, use criss cross

I guess that is the way that I've done retorques, cracking each one at most 1/8 to 1/4 turn, then retorque and progress that way through all of them in a criss cross pattern.  I thought I had heard that to loosen them all and then retorque all of them wasn't correct...but here you hear a different story...

[Perazzimx14]

I do one nut at a time, loosen it and torque, use criss cross

This is the way I do it also.

[lucky phil]

I guess that is the way that I've done retorques, cracking each one at most 1/8 to 1/4 turn, then retorque and progress that way through all of them in a criss cross pattern.  I thought I had heard that to loosen them all and then retorque all of them wasn't correct...but here you hear a different story...

Correct.
Ciao

[Vasco DG]

If you simply loosen one you risk warping the head. It's unlikely but it can happen. With a Guzzi it probably doesn't matter but I still crack 'em all and re tighten. Remember that sliding friction is lower than static friction therefore you want the nut turning right up until crack-point.

Pete

[Morizzi]

If you simply loosen one you risk warping the head. It's unlikely but it can happen. With a Guzzi it probably doesn't matter but I still crack 'em all and re tighten. Remember that sliding friction is lower than static friction therefore you want the nut turning right up until crack-point.

Pete

Oh for Pete's sake!  ::) Pun intended.  :D :BEER:

It shouldn't matter on a LM2. The stud pattern is virtually circular and its not as if you have 6 sockets that are going to unload the studs simultaneously. You have to unload one first. On in line engines you start torquing from the centre and work out. You do it in stages up to the prescribed tension. Unloading is done in the reverse, from the outside in, also in stages.

On a big block tonti pick a stud, any stud and loosen that one just a bit. If you want to do all the studs together it really shouldn't matter. Remember there isn't really an inner and outer due to the circular pattern. As Pete states the torque wrench needs to come up to spec evenly and fluidly so they don't have to be released much.

This isn't the case on small blocks though. They have one 8mm stud and this should be tightened last and released first. There are other makes that have a similar issue. Moto Morinis have a 6mm cap screw between the push rods. This is definitely the last tightened and the first released.

May Santa bring you happiness and a torque wrench to play with!  :BEER:

One final thing, having to remove the rocker arms it is a very good time to check there is no debris in the spindle oil galleries. A simple blow through will confirm this. I have worked on bikes that have been virtually full of rubber bits. I'm guessing from the oil feed line to the heads as if it was the timing tensioner the filter should have caught most of it.

Enjoy the bonding experience.

Rod

[lucky phil]

If you simply loosen one you risk warping the head. It's unlikely but it can happen. With a Guzzi it probably doesn't matter but I still crack 'em all and re tighten. Remember that sliding friction is lower than static friction therefore you want the nut turning right up until crack-point.

Pete

Pete, you back off one at a time maybe 1/2 turn or less just enough to break the thread friction for pulling them  up again
If you think about it when you back them all off you have to start at one of the nuts and do exactly the same thing.
The only difference is here you set the wrench back it off the minimum amount and pull it straight back up again.
Zero chance of actually disturbing the gasket seal.
By far the better method
Ciao

[Vasco DG]

Not the way I was taught and I've yet to have a leaky one. (Shrug.)

Pete

[racasey]

Why we retighten fasteners.  It is not a means of doubling your workload.

In the world of torque, here are two types of joints, hard and soft.  Hard joints are typically metal to metal, like a wheel on an automobile, while soft joints have gaskets and are prone to settling, like a head gasket.  Fasteners are pulled to a tightness that provides a required clamping force.  This force keeps the fastener from coming loose during operation, and keeping things from leaking.  Once a fastener is pulled tight, the effort required to shift it frequently exceeds the original torque value by upwards of 20% to 30%. This is commonly referred to as 'break away torque'.

Since designers know the required clamping force to seal a soft joint like a cylinder head, and they know that soft joints will settle a bit with time and temperature cycles, and the clamping force will in turn diminish, it becomes necessary to verify the original clamping force.  Since there is no practical way to measure clamping force in most applications, the force can be expressed as a torque value and can be accurately applied in the field.  However, breakaway torque prevents the mechanic from verifying the torque load, so he/she is directed to slightly relax the fastener and pull to original specified value.  Hard joints, i.e. lug nuts on wheels almost never require torque verification.

Once pulled up, in most applications there is no need to relax and retorque in stages, simply relax enough to eliminate errors from break away torque and pull to final torque value.  By practice, this is generally done in the original specified sequence.  In most cases, 1/4 turn or less is sufficient to counter break away torque.

On horizontal engines and pumps, the presence of oil and other fluids resting at the joint face readily indicate the hazards of relaxing all fasteners at the same time.  Doing so may promptly wet the gasket.  A BMW boxer engine is an excellent example.

Ciao,
Dick Casey

[rocker59]

Not the way I was taught and I've yet to have a leaky one. (Shrug.)

Pete

Pete,

I was taught your way.  Break them free in a criss-cross pattern.  Re-torque them in a criss-cross pattern.

[redrider90]

Pete,

I was taught your way.  Break them free in a criss-cross pattern.  Re-torque them in a criss-cross pattern.

I have never understand the necessity of re-torquing the head on a Guzzi although like a good boy and not wanting to challenge the "head" gods of torque I have re-torqued the Mille. But someone tell me why?

[Hahnda]

Did the head gaskets on a Morini yesterday. In the manual they have you torque them to 20 ft-lbs, let them sit 30 minutes, then loosen and torque to 15 ft-lbs. They use aluminum head and base gaskets though, also silicone gasket sealer on the head and base gaskets. Ok I guess this really has nothing to do with Guzzi's but just another view on head gaskets and how they get torqued down.

[rocker59]

I have never understand the necessity of re-torquing the head on a Guzzi although like a good boy and not wanting to challenge the "head" gods of torque I have re-torqued the Mille. But someone tell me why?

From my understanding, it is because of the design/material of the gaskets.  On older machines, the gaskets don't maintain their torque over time.

Remember that the gaskets are compressed every time the engine comes up to temperature and that compression is released every time the engine cools.  

Some gasket materials lose their ability to recover from the heat cycles over time, so need to be re-torqued periodically.

Newer, more modern materials used in gaskets on newer engines are more resistant to the heat cycles and don't require re-torquing as often as the older bikes.

[jacksonracingcomau]

I have never understand the necessity of re-torquing the head on a Guzzi although like a good boy and not wanting to challenge the "head" gods of torque I have re-torqued the Mille. But someone tell me why?

Dick's post before yours answered this well
But Guzzi (pushrod) specific 2 things will happen if you don't
1/ valve clearances will tighten up, potentially burning valves, not starting etc etc
2/ head or base gasket may blow, losing compression, chucking oil out of breather etc etc

Best example I was at race meeting once, bloke had hot engine just delivered from tuner that week, was fast.

Came to me to diagnose weird chirping noise
Had blown head gasket to oil drain, actually came out of base gasket, you could see and hear compression coming out. He hadn't been told to retorque, engine builder thought he'd know

My rules
twice cold, once after first hot
After 500 miles check valve clearance, if tight, retorque and reset
Another 1000 check again
When valve clearances stay in spec all is good, won't need retorquing again

Note this only applies to pushrod engines

[Triple Jim]

The valve clearance will tighten up more when you re-torque and compress the head gasket even more.  That would mean that valves should be checked and adjusted after re-torquing.

[jacksonracingcomau]

The valve clearance will tighten up more when you re-torque and compress the head gasket even more.  That would mean that valves should be checked and adjusted after re-torquing.

I think I just said that, but actually very hard not to, you'd be a right plonker to refit tight rocker arms (they have to come off to get to nuts)

But there are plonkers so best underlined, thanks

Loosen adjuster nuts before removing arms

[Triple Jim]

Understood.  I forgot the rocker arms have to come off to retorque.  Thinking of car engines I guess.  But I piped up because it sounded like you were saying that a reason to retorque is that valve clearances tighten up if you don't.

That brings up something I never thought about before (although I'm sure others have).  The unexpected closing of valve clearance could indicate gaskets that are still compressing, requiring retorquing and resetting valves.  So on any pushrod engine, if after a retorque or two the valve clearance is stable, it would mean no more retorques are needed.

[Morizzi]

Loosen adjuster nuts before removing arms

No harm but not necessary. Valve checks are at TDC compression stroke so the gap and thus no tension should already be there. Put a side to that timing point and the spindles should slide out once th retaining bolt is removed.

I always measure before then after the re-torque. You normally find the bike comes back to spec without adjusting the rocker if all is well. If you have no gap at TDC compression then you may want to investigate a bit further.

Just the way I do it.

[jacksonracingcomau]

Understood.  I forgot the rocker arms have to come off to retorque.  Thinking of car engines I guess.  But I piped up because it sounded like you were saying that a reason to retorque is that valve clearances tighten up if you don't.

That brings up something I never thought about before (although I'm sure others have).  The unexpected closing of valve clearance could indicate gaskets that are still compressing, requiring retorquing and resetting valves.  So on any pushrod engine, if after a retorque or two the valve clearance is stable, it would mean no more retorques are needed.

Exactamont, never touch em again if clearances stay.

[jacksonracingcomau]

No harm but not necessary. Valve checks are at TDC compression stroke so the gap and thus no tension should already be there. Put a side to that timing point and the spindles should slide out once th retaining bolt is removed.

I always measure before then after the re-torque. You normally find the bike comes back to spec without adjusting the rocker if all is well. If you have no gap at TDC compression then you may want to investigate a bit further.

Just the way I do it.

Wasn't going to repeat myself again but
If you have retorqued and not adjusted valves at same time, you have achieved precisely









NOTHING

No retorquing was needed, nothing changed. Pushrod is fixed length, compressing the soft gasket reduces the space for pushrod, shows as tight valve lash

To  anybody reading,
If and only if clearances change after first service -- another retorque is called for (sometimes twice, sometimes thrice), do undo adjuster nuts first, this voice of experience tells you that like Rod's uneeded retorquing, setting up soft jaws, clamping rocker arm to undo nut, cleaning arm and refitting it, is wasting time, as I may well be now, Dick's post explained all this hours ago.

[Stevex]

Well, that was interesting. Re-torqued both heads today. One valve on each side had no gap and some of the head nuts required very little effort to undo. Feel a lot better after torqueing them back down to 32lb/ft.

[Antietam Classic Cycle]

Well, that was interesting. Re-torqued both heads today. One valve on each side had no gap and some of the head nuts required very little effort to undo. Feel a lot better after torqueing them back down to 32lb/ft.

You may need to do it several times more.

[charlie b]

Mine took 5 tries to get it right :)

[Morizzi]

Both the Charlie's are on the money.

If you read my post above you will see I measure the valve gaps before and after a re-torque. I only ever re-torque if the gaps have changed but my bike is very consistent. If the gaps are just a bit wider I re-torque and it comes back into spec. I can't tell you how many times it takes but the bike tells me when to do it. You just need to listen to it.

Not sure if you have put new seats in your bike or not but something isn't right. As the heads loosen the gap increases. If you have loose stud nuts and no gap then that is most likely either valve seat recession or valve stretch. The 8mm valve stems on that model are pretty durable but if there is no gap now then that valve would have been partly open during combustion. It may have been annealed soft.

Keep an eye on it and check them more often than you normally would. Hopefully it will all settle.

[Wayne Orwig]

If you read my post above you will see I measure the valve gaps before and after a re-torque. I only ever re-torque if the gaps have changed but my bike is very consistent. If the gaps are just a bit wider I re-torque and it comes back into spec. I can't tell you how many times it takes but the bike tells me when to do it. You just need to listen to it.

That does work on any of my Guzzis.

 ~;

[John A]

Some times I mark the nuts at 12 o'clock with a sharpie so I can visually see how much they move. I think it is important to oil the two external nuts if they are dry , hoping to approximate the friction of the internal nuts.

[Phang]

I have a silly question.

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