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Message started by Kris on 10/24/10 at 19:19:26

Title: How to retorque the HEAD BOLTS
Post by Kris on 10/24/10 at 19:19:26

Hey, could someone please help me out with the torque specs for the 4 head bolts. I think the book said like 20 or so ft. lbs., but I want to be sure since that seeme a little low. Thanks.

Title: Re: Head bolt torque specs
Post by Trippah on 10/24/10 at 19:28:22

I believe all the torque specs are listed in the reference section. ;D
http://suzukisavage.com/cgi-bin/YaBB.pl?board=tech;action=display;num=1098848534

Title: Re: Head bolt torque specs
Post by BurnPgh on 10/24/10 at 19:29:59

22 - 24 ft/lbs iirc. or something close anyway.

Title: Re: Head bolt torque specs
Post by Oldfeller on 10/25/10 at 05:36:05

Item to be aware of: Stretch

Cylinder studs like to twist and stretch, stretching is after all how they operate. They are linear action springs, holding everything together against compression and explosions simply by the linear elongation tension they develop by being torqued down.

This is why it is important to remove one stud nut at a time, grease or oil it and its threads liberally, install it and turn it down by finger force and then torque it to the required number (21-24 foot pounds on our bikes) in a single motion using an accurate torque wrench.

Why grease the threads? If you don't you WILL loose yourself in friction/stiction and in cylinder stud twist and you won't get what you think you saw on the torque wrench. Nothing even close to it.

Next, back to stretch --- tighten it down to 24 foot pounds, give it half an hour and go back and it will be sitting at 21 foot pounds. So you snug it up again, and a half hour later it is sitting at 20.5 foot pounds.

You could keep doing that until the stud pulls in two you know -- the stud is stretching some every time you pull it up to value.

===============

Torque wrenches are interesting beasts -- clicker types only claim to be 3-5% accurate. And that's when they are brand new and the grease on the click over point is new, etc. What are they when they get old and crusty or worn?

5% of 21-24 foot pounds is 1.2 foot pounds, like half the range that you are shooting for in the torque spec.

A good name brand beam and pointer wrench of the appropriate (not a huge span going way past what you want) range is the most accurate, most durable tool for torquing things down. Plus, it is good to see you are approaching what you want and you can also see that the pull up has been all smmmooooth and stiction free.

Nothing more disgusting that using a clicker wrench and thinking "did I miss that durn click again?"

Title: Re: Head bolt torque specs
Post by Kris on 10/25/10 at 06:28:39

So even with the stretch, and long as i grease those threads, and get a torque of 24ft lbs the first time, i'm good to go? Even though that torque will be less in a little while? The issue i'm having is that the main oil gallery is leaking over to one of the studs via my head gasket. That's why I want to make sure i'm giving it the correct torque. I have a new head gasket coming in today, so i want to be extra sure i've got the right specs. Thanks for everyone's help on this.

Title: Re: Head bolt torque specs
Post by Oldfeller on 10/25/10 at 07:26:35

There is an "O" ring seal involved in the head cover to head junction over the oil passage that you mention. Base gasket is a plain paper gasket (so use a thin coating of gasket sealer), the head gasket is rubberized steel with raised spring lips around the critical oil passages, so it will seal itself under compression with no gasket sealer needed.

Leave anything out by chance?

And yes, on a virgin gasket stack installation, I would go back after 24 hours or so and pull it back up to torque again one time -- the gaskets compress over time and the sealant oozes before it sets up good, so you have some pressure relief apart from the stud stretch to recover from.

Motorcycle makers don't do this, they tell you to do it after 600 miles so you get to pay their dealership big bucks to have it done.

We have many bikes on the list that never got re torqued that did just fine, so don't get all excited over it, just do it after 24 hours if you have the chance.

Title: Re: Head bolt torque specs
Post by Digger on 10/26/10 at 21:02:02

07242C2E2D24242D3A480 wrote:

....Next, back to stretch --- tighten it down to 24 foot pounds, give it half an hour and go back and it will be sitting at 21 foot pounds. So you snug it up again, and a half hour later it is sitting at 20.5 foot pounds.

You could keep doing that until the stud pulls in two you know -- the stud is stretching some every time you pull it up to value......

Old,

If ur sayin' what I think ur sayin, I'm not buyin' it. Not if the studs have not reached their elastic limits.

I suppose the phenomenon you are describing could be due to gasket settle, etc, but if the studs themselves are responsible, then their elastic limit has been exceeded and they are now into yield. Which would not be good.

Or am I all wet? :-/

Title: Re: Head bolt torque specs
Post by Oldfeller on 10/27/10 at 12:47:58

Well, think on it a little bit.

The studs have a reduced section for a reason -- the reduced section defines the settle tension the fastener is capable of.

You can't torque past 24-25 foot pounds, it just turns on more as it stretches the stud even more.

Your settle down torque drops slightly each time if you keep going back and rechecking.

Logically, if you kept at it (or tried for 36 foot pounds like somebody said) I think you'd get an immediate answer to your question.

Then you could tell all of us all about it. ;D

(I pulled mine up 3 times after 24 hours when I put my cam in -- its fairly fresh to me that the last 2 were not helping anything very much. It would start at 20-21, go to 24 then relax back over a few hours to right back where it started from, minus a smidgen.)

Title: Re: Head bolt torque specs
Post by rokrover on 10/28/10 at 07:59:28

Digger - you are correct about bolts being tightened past the elastic yield point. Bad - and you should never reuse these. Some bolts are deliberately designed this way (big-end bearing caps come to mind) as the bolts then have a flat stress-strain curve past the yield point and exert more consistent clamping force. However, they must be replaced once removed. The Suzuki has 6 head bolts - the four big studs and the two bolts underneath front and back. I would never remove just one at a time to grease as then you risk warping the head. Just like tightening, you gotta loosen all in a criss-cross sequence a bit at a time. I doubt Suzuki meant these to be torqued past the elastic yield but I did have a similar problem getting the front bolt under the head to stay tight. Also, you can not set an accurate torque on a tight nut and need to back it off first about thirty degrees then bring back up to spec with the specified lube, usually just engine oil. Some specs call for tightening head bolts with a final twist angle and not torque value because of errors caused by thread lube. Hope this helps.

Title: Re: Head bolt torque specs
Post by Digger on 10/28/10 at 22:01:27

504D49504D544750220 wrote:

rok,

Good words!

I've been tightening those two groups of nuts (upper and lower being the two groups) separately.

What you say makes sense. Now I believe they should all be loosened/tightened all together.

Thanks....I'll change my written procedure accordingly.

Title: Re: Head bolt torque specs
Post by Oldfeller on 10/29/10 at 03:25:40

We are talking re-torque here -- not original assembly

On a re-torque, loosening one nut at a time leaves 3 (or 5 if you count the underside nuts) fasteners to maintain clamp force on the head gasket.

Why is this important?

The head gasket is rubberized spring steel material that has raised "bumps" or spring lips stamped into it -- it is a spring washer type rubberized gasket.

If you loosen all the fasteners on a re-torque then the spring lips will jack the gasket/head/jug surface apart separating the rubber from the gasket and/or a machined surface allowing oil to migrate into that surface junction area.
(and free oil is available to those surfaces, we all know about that. Got oil galleries and cam chain passages, etc to supply it.)

When torque is re-applied, the separated rubber surface doesn't make an oil proof joint again (it can't -- it is torn/separated and oil is already in there).

Head gasket leaks are much more likely after undoing all the fasteners on a re-torque. So are the paper gaskets, but they do not have spring lip action to guarantee that they separate like the head gasket does.

===========================

Now, please explain in small words the evil that is done by only loosening one nut so you can grease the threads so you get an accurate re-torque? I didn't quite follow the logic since you were talking about required replacement fasteners like the cap end bolts on a car (????).

Which fasteners on our Savage are "required replacement fasteners"?

The spring lips on the head gasket put out forces in the hundreds pound range, the clamp force on the entire head surface from all the fasteners together is likely in the 1,000s pound range. Taking one fastener free at a time isn't allowing anything to move (the surfaces remain clamped with force over 1000 pounds and are quite stationary).

Yes, the load vectors shift but the joint does not ever move when loosening only one fastener at a time -- that's why we do it that way.

If you want to make a fetish out of the alternating final pull up that is done with a new gasket assembly (which nobody is arguing with, btw) and confuse it with the retorque scenario which requires you to lube the threads of the fastener which do require you to remove it and lube it and retorque it one at a time then you are gonna confuse the newbies to no end.

Two different scenarios -- two different sets of requirements -- two different methods.

Title: Re: Head bolt torque specs
Post by Digger on 10/29/10 at 19:11:10

Well, now I'M confused, and I'm not a newb!

Here is what is found in the Suzuki Factory Service Manual (FSM) regarding the re-torque procedure (the 9mm nuts mentioned in the procedure are the four head nuts at the top of the head, the 8mm nuts mentioned in the procedure refer to the two nuts below the head (one forward of the head and one aft of it)):

Apply engine oil to the four 9mm nuts and retighten the four 9mm and two 8mm nuts to the specified torque with a torque wrench sequentially in diagonally (sic) with the engine cold.....

The next step in the procedure says to replace the rubber plug, and the next step begins with:

After firmly tightening the six nuts....

So, IMO, even though the FSM never explicitly addressed the loosening of the nuts, I believe it DOES call for you to loosen ALL SIX nuts, then to retighten all six diagonally.

Now, in contrast to this, the Clymer manual for this bike (2005 edition), says to (again, referring to the re-torque procedure):

Using a crisscross pattern, loosen and remove all cylinder head nuts. (Digger's note: They are referring to the four nuts at the top of the head here.)

Apply engine oil to the nuts.

Tighten the cylinder head nuts in a crisscross pattern....

Tighten the cylinder head-to-cylinder nut at the front and at the rear....

Although the Clymer procedure is a bit different than the one found in the FSM (in that it has you completing the re-torque operation on the four nuts at the top of the head before proceeding to the two nuts at the bottom of the head), they agree in that both procedures have you loosening more than one nut at a time.

Thoughts?

Title: Re: Head bolt torque specs
Post by Digger on 10/29/10 at 19:16:36

50737B797A73737A6D1F0 wrote:

.....Now, please explain in small words the evil that is done by only loosening one nut so you can grease the threads so you get an accurate re-torque?....

Old,

To my way of looking at it, the head assy is flexible, just as if it were made from rubber. Although it is made of something much stiffer than rubber, it will still flex under loading like rubber would (just not nearly as much).

By completely releasing the tension on one head nut while leaving the other five tight, you are introducing warping strains to the head. Which can't be good.

What is the right answer here?

Title: Re: Head bolt torque specs
Post by BurnPgh on 10/29/10 at 22:04:56

7A5951535059595047350 wrote:

Item to be aware of: Stretch

And if you actually tried to pull it up to 36 foot pounds as said earlier -- pop goes the weasel !!! You ain't ever gonna get there ....

Not necessarily. Ask me how I know. Luck I didnt strip the studs...but I didnt. And Its been running just fine. Though if/when I plan another top end tear down I do plan to have new studs ready.

file this little incorrect recollection of mine under "lucky"

Title: Re: Head bolt torque specs
Post by Oldfeller on 10/30/10 at 02:04:07

Digger, this whole thing has been a debating point since I first got here. Back then, it was about the necessity of getting oil (or grease) on the threads of the studs/nuts so things would pull up right.

Just putting oil over the tops of the engaged fasteners just doesn't do the job, they still stick and twist the studs when you retorque unless the lube is worked deep into the fastener and the lube is heavy enough to withstand the torque you are laying down on it. Light oil or penetrating oil simply won't do the job.

The discussions then became grease vs oil (I like never-sieze personally for the grease as it sticks around in the joint pretty good for next time).

Then it was all about how to get it in there without breaking the head gasket compression bond.

============================

That was back then, now it seems its about people talking about different scenarios of applying a torque job,

one is talking a new virgin stack pull up (yes, alternate in a pattern and pull up slowly with grease on the threads)

one is talking recovering from an overtorque (if you went to 36 ft pounds, then yes you probably went past the elastic point into deformation)

one is talking simple retorque according to Suzuki full shop manual (which goes all the way back to the original discussion wars)

And nobody is really clarifying which one they are speaking to and it is possibly confusing to a "unclarified" reader down the road a bit.

============================

And about them mythical newbies -- they are the really green dudes that dig up your posts years after you make them and and repost them along with the trouble they got into for partially following them.

(what little they understood, anyway)

Them Durned Newbies have done some whacked stuff before on this list -- so I try to consider them when posting critical or dangerous stuff.

More so now than I used to, anyway.

::)

Title: Re: Head bolt torque specs
Post by Russ130 on 03/05/11 at 20:58:47

I'm with you Oldfeller. There is no way I'm gonna remove all the nuts and then trust that it will be ok after retorqueing them. I might be a newbie to the Savage or even bikes but I've turning wrenches my whole life. On something as critical as a head gasket the last thing you want is for something to move even the smallest fraction of a mm. Hot rod magazine did an article on this years ago. They had all kinds of microscopic photos and it was determined that you should not retorque head bolts more than one fastener at a time. In fact it is recommended to not even touch them again period. By the same note I had a snapper mower that needed the head bolts torqued down frequently just so it would start, apparently a real common problem on those since that is what the tech where I bought the mower said to do. So I would think somewhere in the middle is our Savage that needs periodic retorqueing. Not sure why but if it is a common thing to do and my head cover is already off as it is, then I will do it now.