Alfa Romeo Forums banner

1 - 19 of 19 Posts

·
Registered
Joined
·
229 Posts
Discussion Starter #1
I put my cylinder head back on last weekend. The engine is out of the car. My Tech Spec manual it states that I must "slacken and re-tighten without lubricating" although the engine workshop manual doesn't mention it.

So do I slacken them all in the sequence shown for head removal (so then they will all be loose) and then re-tighten them all in the sequence shown for head installation?

What's this process for? Won't I just end up where I started?

Thanks.
 

·
Push hard and live
Joined
·
9,616 Posts
Are you working on a 1900, 2000, or 2600? It doesn't really change the advice, but we might direct you to more specific guidance.

In general, there is a head-tightening process that helps ensure against future gasket failure. The process for the later engines is probably a good place to start, as I don't believe the details that were developed over time were re-stated specifically for the 102/106 engines.

Anyway...

One should make sure all of the threads on the studs are as clean and smooth as possible.

Lubricate both the threads and the washers prior to initial installation of the nuts. I use a home-brew mixture of oil and graphite, but the ARP lubrication is very, very good in delivering consistent results.

Tighten the nuts in the sequence shown in your shop manual. I bring them up in equal increments of about 10 ft-pounds, working toward the specified torque value. Note that I have learned that click-type torque wrenches are a poor choice for high-torque applications such as cylinder head, main, and rod fasteners. Better to use a beam-type or modern buzz-type so you can hold the specified torque value while the rotation "creeps" to a final stop.

After the freshly overhauled engine has been fully torqued, I go away and celebrate with a glass of my favorite wine.

A day or so later, I return, and loosen each nut one at a time, pulling it back to its targeted torque value, again allowing time for it to creep to a stop with a beam type wrench. It is amazing how much difference in tension is achieved when properly lubricating the fasteners (and washer) and using the slow-creep approach vs incorrect or missing lubrication and a click-type wrench.

Then, the Alfa guidance is to run the engine and while it is hot, pull each nut in sequence up a bit. The actual amount of increase is somewhat in debate, but I think the Alfa recommendation is 5 more pounds of torque. Thus, if the original targeted value was, for example, 55 lbs, then you would increase it to 60 pounds while the engine was warm. You would do this WITHOUT loosening prior to the re-tightening.

Then, after some amount of use (perhaps 300 miles - although again there is some discussion on this), you re-tighten the head much as you did originally, ie loosen each nut and retighten it to the cold value. Before doing this, it is recommended that you drain some of the coolant so it doesn't sneak past a slightly loose gasket and mess up your life later. An alternative method is to open the radiator cap, squeeze the upper hose, and while holding the squeeze replace the radiator cap. This puts a little vacuum into the cooling system, preventing it from leaking past a loosened gasket.

Again, after driving it to get it warm, pull up the nuts to the previous maximum target. Some people use 55 as the max, others 60, 65, or even 70. I don't know what engine you have, so you'll want some specific guidance on this. I use 60 lbs on my 102 engines, but their cast-iron blocks and lack of wet cylinder liners sort of changes a lot of dynamics compared to the all-aluminum wet-sleeve engine.

Although your apparent torque value will end up as it was before, the actual tension on the gasket will be quite different. First of all, the gasket will compress a bit after assembly and running. Thus, if you just left the "torque" setting uncorrected, the actual pressure on the gasket would have decreased, leading to a probable failure. Also, various things expand when hot, so pulling up the extra torque while warm ensures that you have removed all possible below-spec tension on the head studs, and therefore gasket.

I encourage you to research the concept of tension and how torque is, at best, an indicator of the achieved tension. People seem to fall in love with "torque" without grasping what we are really trying to do, which is achieve a very specific tension within a fastener. If you take a little time to study it, it all makes good sense.


I predict others will add their opinions, some perhaps contradictory. Feel free to ignore my advice. It was free.
 

·
Registered
Joined
·
9,409 Posts
Further to Don's comments, here's how Alfa described the procedure in 1968 (for 1300, 1600, 1750):
 

Attachments

·
Registered
Joined
·
229 Posts
Discussion Starter #4
Thanks both - its a 2600. I only have a click torque wrench so that will have to do but it's new and good quality.

I didn't lubricate the threads/washers before 1st tightening - but everything was very clean.

So when I slacken off, do I need to lubricate given that I failed to do that the first time, bearing in mind that the manual says for the 2nd (cold) tightening, don't lubricate?
 

·
Push hard and live
Joined
·
9,616 Posts
I will apologize up front, but my perspective is of someone who (before I retired) taught various instrumentation and maintenance techniques. Some of my customers were in positions where a mistake could cause death. I take it seriously when someone performs a maintenance technique in a manner that can be dramatically incorrect.

The goal of torquing is to achieve a specified tension. The torque value itself is irrelevant, it is the tension that is holding together a system in a manner that will endure.

General automotive practice is to lubricate all threads. Some manufacturers can be quite specific on what lubrication to use, but in general motor oil is better than nothing. Torquing without lubricating means you definitely did not achieve the intended tension.

The threads of an old and used system can be quite rough when you look at them under a magnifying glass. Often, chasing them with a redressing die will improve things. All that roughness will reduce the tension achieved for a certain amount of torque.

The single biggest variable in correct establishment of torque is friction. The accuracy of the torque wrench is generally much, much less significant than the friction. By this, I mean that the friction builds up in a non-linear way as the tension is increased. If all threads are new, and everything is lubricated as instructed, you should achieve the design-spec tension at a certain torque value. You won't achieve the design-spec at the first moment the wrench reaches that torque value, but you will after the bolt or nut finally stops turning. If you have new threads and good lubrication, it will "creep" a long way from the first moment it achieves the targeted torque. If you have rough threads and no lubrication, the first moment you reach the specified torque, your wrench goes "click" and you are probably many thousands of PSI below spec on the tension.

Thus.

Good, clean, smooth threads.
Good lubrication
Beam or buzz type torque wrench.

Plenty of people use click wrenches and believe "click" means they have achieved the design tension. They have not.

But, heck. It's your engine, so have fun. I would start all over doing it the right way. You'll find that this is faster than replacing a blown head gasket later.
 

·
Registered
Joined
·
13 Posts
I had new head gasket installed retorqued by experience ed alfa shop. After driving 4 to 500 miles.coolant was heavily,.in my opinion contaminated with oil. Flushed engine but was warned it would not be 100% since it is California?
Is residual oil a universal problem?
Reflushing test and retorquing to try and confirm a good gasket before tearing it apart.
Any experience?
Failed to say it is spider veloce.
 

·
Registered
Joined
·
9,409 Posts
Thanks both - its a 2600. I only have a click torque wrench so that will have to do but it's new and good quality.

I didn't lubricate the threads/washers before 1st tightening - but everything was very clean.

So when I slacken off, do I need to lubricate given that I failed to do that the first time, bearing in mind that the manual says for the 2nd (cold) tightening, don't lubricate?
Don's description is quite correct with respect to friction, torque creep, etc. -- therefore, applying oil on the first or second torquing would not create the same result. Applying oil for the first torque provides prescribed friction and leaves a thin film of oil on the threads to protect them from corrosion. The heat expansion and vibration from running the engine (in context of pressure and oil viscosity) make the lubrication film thinner. After the engine cools down, the head and bolts contract slightly, which is why Alfa added the 3rd torquing step.

In order for bringing the torque values into spec, I suggest you start over with the process (one nut at a time, in the prescribed sequence): Remove the nuts, clean the threads, oil the threads and washer, torque to first value. Then, warm up the engine by driving the car, and do the second torquing. Let it cool down and do 3rd torquing. As for click torque wrenches, I think quite a bit of progress was made over the last 50 years (but Don's point is still valid -- and I would add: Any torque wrench is useless unless it has been calibrated).
 

·
Push hard and live
Joined
·
9,616 Posts
manners

Steve, it is considered poor form if a person asks for help, gets it, then insults the one who provided the help.

I don't take tablets. I take lives quite seriously, however. I have personally known some to be lost due to poor maintenance practices. For me, this is not theoretical.


You were a teacher? That must have been a nerve-wracking experience for your students. Keep taking the tablets Don.
 

·
Push hard and live
Joined
·
9,616 Posts
"As for click torque wrenches, I think quite a bit of progress was made over the last 50 years (but Don's point is still valid -- and I would add: Any torque wrench is useless unless it has been calibrated)."

Ruedi, you are right that technology continues to provide fancier tools. That can be a good thing. However, what I've watched is an increasing belief in the tools while losing an actual understanding of what is going on. Thus, they use the tools incorrectly.

I can walk you through the math (it would be tedious for everyone) how the likely range of mis-calibration in a modern torque wrench is smaller than at least two other variables that can negatively impact achieving the correct tension, and possibly more. However, it is relatively easy to understand and achieve a certified calibration, whereas technique and system preparation are just not taught, nor are they obvious to hobbiests. Heck, they are increasingly not taught to professionals, as manufacturers have adopted more predictable and repeatable ways to achieve a specific tension than simple torque values.

Focusing on the wrench generally leads to the "I cut it twice, but it's still too short" sort of result.
 

·
Registered
Joined
·
3,937 Posts
Don, Thank you for taking the time to share your knowledge.

Roy did Experienced Ed's Alfa Shop install roll pins in your 1600's block and new o-rings with the head gasket? Hopefully they have stopped the oil leak. Residual oil may cause rubber parts like your radiator hoses to soften and swell over time. Don't know what California has to do with anything...

Mark
 

·
Push hard and live
Joined
·
9,616 Posts
Mark,

The problem is, I can willingly be quite the smarta$$ myself. The challenge is to realize when your target is on a subject that has deep, and profound, personal importance. The correct reply then is "thank you".
 

·
Registered
Joined
·
3,937 Posts
Mark,

The problem is, I can willingly be quite the smarta$$ myself. The challenge is to realize when your target is on a subject that has deep, and profound, personal importance. The correct reply then is "thank you".
You are absolutely correct on both points I have edited my previous post where I stated "I appreciate you taking the time to share your knowledge". :wink2:

Steve, you'd be wise to follow Don's advise so you do not end up in a situation like Roy. I believe the manual says to lubricate the head bolts and studs prior to applying torque the first time. The second step does not require that you remove the lubricant, it is just saying to re-torque the head without applying (additional) lubricant. Something must have gotten lost in the translation from Italian to English.

On the three head gasket replacement jobs that I have done, including one Duetto engine rebuild 30 years ago, I cleaned the head studs lightly with a wire brush, cleaned the head nuts/washers and lubed them with oil. I did learn to only loosen one head nut at a time so as to prevent coolant seepage into the oil when re-torquing. If I ever do another, I'll have to remember the trick to squeeze the radiator hose though. I agree that the deflecting beam torque wrench is the better way to go (although I still use my "once calibrated" click type torque wrench on my lug nuts, just so I don't have to look at the scale while I am straining:). I also like it that the beam torque wrench has a pivot in the handle to help you apply accurate torque; the handle should be 'floating' at the pivot point. The click type does not have this feature so your moment arm can vary a few inches either way; perhaps it does not matter...

"Dry" torque values would tend to be very inconsistent and I believe the more important thing is to have uniform and consistent tension on the head studs. I'd be happy a few pounds high or low as long as the torque values (tension on the stud) are all very close.

Mark
 

·
Registered
Joined
·
300 Posts
Don, Ruedi, Mark and others, thanks for taking the time to post this information about torque and torque wrenches. I did not know the advantages of using a beam-type torque wrench. Much appreciated,
Larry Bono
 

·
Registered
Joined
·
229 Posts
Discussion Starter #16
Thanks

I've always been grateful for advice given in the past and on this occasion was over-sensitive about how some of it was conveyed. Apologies to Don and thanks to all.
 

·
Push hard and live
Joined
·
9,616 Posts
As I'm currently sitting in the room of ceramic contemplation....

As I mentioned, engine manufacturers are increasingly specifying techniques for reassembling their engines, after they've been in use for a while and accumulated corrosion, roughness and distortion in the threads and bolting surfaces. I think the one used on some Ford V8s is a good example.

There is guidance to bring the head bolts up to a certain torque in a specified sequence. Then, each bolt is turned 90 more degrees without respect to the "torque" required to do so.

The impact of age and wear (corrosion, burrs, scoring, etc) causes a non linear increase in rotational friction the higher the tension. The tension itself is a function of thread pitch and bolt plasticity. Thus, if the only method to achieve a necessary tension is to stop turning at the first moment a torque value is reached, the results of a new system will be quite different from an aged/used system. The Ford approach uses torque up to the point where the age/used friction factors don't dominate. After that, they know how much tension will be achieved by the additional 90 degree turn.

In engines which don't have these interesting solutions, the best we can do is ensure clean, smooth, well lubricated threads and surfaces, and a torque wrench that will allow you to maintain the specified torque value until the fastener stops moving. With a new new uncompressed head gasket, I have often seen a head nut/bolt that was set to the specified torque value with a click-type wrench pull an additional 90 degrees with a beam or buzzer type. That is a LOT of additional tension.

Click-type wrenches, in my experience, are best reserved for assembly-line fabrication of new components where it is important to not exceed a failure point of a fastener. Speed is important to profits, and the designers have calculated the statistical results for reliability.
 

·
Registered
Joined
·
216 Posts
as manufacturers have adopted more predictable and repeatable ways to achieve a specific tension than simple torque values
In industry we call this making something idiot resistant. We also have to take into account the idiot force. It is because with enough idiot force, any system can be overcame.:grin2:
 

·
Push hard and live
Joined
·
9,616 Posts
Some scientists claim that hydrogen, because it is so plentiful, is the basic building block of the universe. I dispute that. I say there is more stupidity than hydrogen, and that is the basic building block of the universe.

F Zappa

Also...

I have found that the degree to which a person or organization vigorously defends a faulty technique is in direct proportion to how much has been invested in that technique.

I particularly enjoyed it when a German lady chemical engineer in charge of the process control at a very large chemical plant (the name is often associated with aspirin) said to me after a class...

"I see that you are correct, but I don't agree."

And so it goes....
 
1 - 19 of 19 Posts
Top