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cylinders studs M8

Started by louloupa, November 24, 2019, 09:55:45 AM

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louloupa


is it essential to change the cylinder studs and bolt nuts at each disassembly  / reassembly of the heads ?

Pirsch Fire Wagon

Tom


Dan89flstc

November 25, 2019, 05:47:21 AM #3 Last Edit: November 25, 2019, 06:06:16 AM by Dan89flstc
The service manual does not require new nuts or studs.

If the setup were torque to yield, the stud would be the part that was not reusable, but this is not the case here, they are not torque to yield.

There is a lot of misconception about torque to yield on the internet.

Just because a fastener is torqued and then turned to a certain amount of degrees does not mean it is a torque to yield fastener, in this case it is simply a more accurate way of tightening the fastener.
US Navy Veteran
A&P Mechanic

Admiral Akbar


kd

KD

louloupa

Yes , very interesting

To sum up : you just need to change the stock nuts et replace by S&S reusable nuts  (or, new HD nuts ) .   

Thanks

rbabos

The issue as I see it has always been the QC on these head nuts. Likely hydrogen embrittlement from the plating process or material used. You can't tell me that the twin cams head torques weren't as equally fkd up, yet next to no breakage. Not a fan of incremental torque as it multiplies the errors. There's no way that all 4 head bolts have the same friction zone at the head contact.
Ron

Admiral Akbar

November 25, 2019, 06:36:02 PM #8 Last Edit: November 25, 2019, 08:25:00 PM by Admiral Akbar
Quote from: rbabos on November 25, 2019, 09:48:05 AM
The issue as I see it has always been the QC on these head nuts. Likely hydrogen embrittlement from the plating process or material used. You can't tell me that the twin cams head torques weren't as equally fkd up, yet next to no breakage. Not a fan of incremental torque as it multiplies the errors. There's no way that all 4 head bolts have the same friction zone at the head contact.
Ron

Maybe I can. As I understand it M8 use 7/16 studs not 3/8 like TCs.  Think about that one for a while.

Add: what do you mean by incremental torque?  10-20-30-40?  or 10-20-30 + 90 deg?

rbabos

Quote from: Admiral Akbar on November 25, 2019, 06:36:02 PM
Quote from: rbabos on November 25, 2019, 09:48:05 AM
The issue as I see it has always been the QC on these head nuts. Likely hydrogen embrittlement from the plating process or material used. You can't tell me that the twin cams head torques weren't as equally fkd up, yet next to no breakage. Not a fan of incremental torque as it multiplies the errors. There's no way that all 4 head bolts have the same friction zone at the head contact.
Ron

Maybe I can. As I understand it M8 use 7/16 studs not 3/8 like TCs.  Think about that one for a while.

Add: what do you mean by incremental torque?  10-20-30-40?  or 10-20-30 + 90 deg?
This. Highly dependent on equal friction on all 4 studs to end up the same stretch.
Ron

Admiral Akbar

Quote from: rbabos on November 26, 2019, 06:37:06 AM
Quote from: Admiral Akbar on November 25, 2019, 06:36:02 PM
Quote from: rbabos on November 25, 2019, 09:48:05 AM
The issue as I see it has always been the QC on these head nuts. Likely hydrogen embrittlement from the plating process or material used. You can't tell me that the twin cams head torques weren't as equally fkd up, yet next to no breakage. Not a fan of incremental torque as it multiplies the errors. There's no way that all 4 head bolts have the same friction zone at the head contact.
Ron

Maybe I can. As I understand it M8 use 7/16 studs not 3/8 like TCs.  Think about that one for a while.

Add: what do you mean by incremental torque?  10-20-30-40?  or 10-20-30 + 90 deg?
This. Highly dependent on equal friction on all 4 studs to end up the same stretch.
Ron

So is this important if the gasket doesn't settle?  If the case / cylinder / head stackup doesn't change, what difference does it make to "torque to stretch" compared to "torque to load"?

rbabos

Quote from: Admiral Akbar on November 26, 2019, 06:53:33 AM
Quote from: rbabos on November 26, 2019, 06:37:06 AM
Quote from: Admiral Akbar on November 25, 2019, 06:36:02 PM
Quote from: rbabos on November 25, 2019, 09:48:05 AM
The issue as I see it has always been the QC on these head nuts. Likely hydrogen embrittlement from the plating process or material used. You can't tell me that the twin cams head torques weren't as equally fkd up, yet next to no breakage. Not a fan of incremental torque as it multiplies the errors. There's no way that all 4 head bolts have the same friction zone at the head contact.
Ron

Maybe I can. As I understand it M8 use 7/16 studs not 3/8 like TCs.  Think about that one for a while.

Add: what do you mean by incremental torque?  10-20-30-40?  or 10-20-30 + 90 deg?
This. Highly dependent on equal friction on all 4 studs to end up the same stretch.
Ron

So is this important if the gasket doesn't settle?  If the case / cylinder / head stackup doesn't change, what difference does it make to "torque to stretch" compared to "torque to load"?
Torque to load in increments has frictional errors effecting the final number. Let's take a look at an example in my case, the v rod, since have the figures. The head bolts are first torqued to 25'lbs. Uses Cometic gaskets so the first torque is nothing more then to burnish the contact surfaces since the gasket has no settling effect. The bolts are backed off and then all 4 torgued to 15'lbs, then 90* on each from there. The frictional errors between bolts at 15'lbs is very small compared to say 30'lbs. If you look at the thread of a bolt an think of it as a micrometer, a given rotation in degrees will always produce the same distance. If the 4 bolts are rotated 90* the final torque between them will be just about identical or as close as humanly possible. Now, the vid part I had issue with. If one was to take those 90* rotated bolts and apply a torque wrench to compare differences, damn straight they will not match up. Incremental torques done will likely match up closer on the wrench but since friction is effecting the reading, the stretch or equal clamping loads will not be the same. The initial and degree method,  friction will be different between them at the end to effect the wrench torque reading if one checks, even thought they are loaded in stretch about the same amount. In the end goal, what's more important, the wrench go click or have all 4 studs clamping closer to the same amount? Now, don't get me wrong, as there's still some old school in me, so I've done it both ways but prefer the degree method overall if the spec is given. In 60 year old aircraft engines for example that spec wasn't dreamed up yet, so it's torque to load. :hyst:
Ron

Dan89flstc

Quote from: rbabos on November 26, 2019, 07:26:13 AMIn 60 year old aircraft engines for example that spec wasn't dreamed up yet, so it's torque to load. :hyst:
Ron

As a jet engine mechanic for over 45 years, I can tell you that the torque and degree method was indeed used 60 years ago (in some jet engines at least)... :SM:

US Navy Veteran
A&P Mechanic

Admiral Akbar

Quote from: rbabos on November 26, 2019, 07:26:13 AM
Quote from: Admiral Akbar on November 26, 2019, 06:53:33 AM
Quote from: rbabos on November 26, 2019, 06:37:06 AM
Quote from: Admiral Akbar on November 25, 2019, 06:36:02 PM
Quote from: rbabos on November 25, 2019, 09:48:05 AM
The issue as I see it has always been the QC on these head nuts. Likely hydrogen embrittlement from the plating process or material used. You can't tell me that the twin cams head torques weren't as equally fkd up, yet next to no breakage. Not a fan of incremental torque as it multiplies the errors. There's no way that all 4 head bolts have the same friction zone at the head contact.
Ron

Maybe I can. As I understand it M8 use 7/16 studs not 3/8 like TCs.  Think about that one for a while.

Add: what do you mean by incremental torque?  10-20-30-40?  or 10-20-30 + 90 deg?
This. Highly dependent on equal friction on all 4 studs to end up the same stretch.
Ron

So is this important if the gasket doesn't settle?  If the case / cylinder / head stackup doesn't change, what difference does it make to "torque to stretch" compared to "torque to load"?
Torque to load in increments has frictional errors effecting the final number. Let's take a look at an example in my case, the v rod, since have the figures. The head bolts are first torqued to 25'lbs. Uses Cometic gaskets so the first torque is nothing more then to burnish the contact surfaces since the gasket has no settling effect. The bolts are backed off and then all 4 torgued to 15'lbs, then 90* on each from there. The frictional errors between bolts at 15'lbs is very small compared to say 30'lbs. If you look at the thread of a bolt an think of it as a micrometer, a given rotation in degrees will always produce the same distance. If the 4 bolts are rotated 90* the final torque between them will be just about identical or as close as humanly possible. Now, the vid part I had issue with. If one was to take those 90* rotated bolts and apply a torque wrench to compare differences, damn straight they will not match up. Incremental torques done will likely match up closer on the wrench but since friction is effecting the reading, the stretch or equal clamping loads will not be the same. The initial and degree method,  friction will be different between them at the end to effect the wrench torque reading if one checks, even thought they are loaded in stretch about the same amount. In the end goal, what's more important, the wrench go click or have all 4 studs clamping closer to the same amount? Now, don't get me wrong, as there's still some old school in me, so I've done it both ways but prefer the degree method overall if the spec is given. In 60 year old aircraft engines for example that spec wasn't dreamed up yet, so it's torque to load. :hyst:
Ron

Then how do you explain what  the guy in the video is seeing?   Why wouldn't the clamping for on the be the same if the  all the surfaces were machined with the same process? 

Not dissing the 90 deg method but is it the best here especially since the head studs are 36% stronger?

rbabos

Quote from: Dan89flstc on November 26, 2019, 08:31:23 AM
Quote from: rbabos on November 26, 2019, 07:26:13 AMIn 60 year old aircraft engines for example that spec wasn't dreamed up yet, so it's torque to load. :hyst:
Ron

As a jet engine mechanic for over 45 years, I can tell you that the torque and degree method was indeed used 60 years ago (in some jet engines at least)... :SM:
Out of my pay grade and never got to work on one as an amateur , experimental category in your country. I speak the old baffed out Lycoming and Continental on my budget.
Ron

louloupa


I think that the method in degrees is more accurate than that by torque . there is no influence by friction . All modern cars use it.

FXDBI

Good video .  Many years ago I was taught to use smaller steps and more of them and to always go around with the torque wrench at each level until they are all the same, never just one click.  Also learnt to let it relax for 15-20 mins  and re-torque to final spec.  Way to many in a rush to re-assemble things, its not a race. Only time I have ever used degrees is after a stud has been measured and your looking for bolt stretch. Don't over think it. I have a old clark compressor manual that has torque measured in hits with a 16lb hammer by a average man, that's about how accurate them cheap junk torque wrench's are anyhow.  Bob