Sheared Off Cam Bearing Studs - BMW Luxury Touring Community
 
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post #1 of 22 Old Mar 24th, 2010, 11:59 pm Thread Starter
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Sheared Off Cam Bearing Studs

An interesting twist on an otherwise uneventful, but pleasurable task. I used to do this drill all the time on my '62 Jaguar. Much the same. Imagine my dismay when I am torquing down the bearing caps carefully, 1/4 turn at a time, criss-cross pattern, starting at the middle and working toward the ends when I hear "click". Good, I say, finally reached the torque setting (80 in lbs) according to Clymer. But alas, the nut and the first inch of the stud kerplunk down on my stand. Not good. Thankfully, there's a good 2 inches of stud exposed when I remove the bearing cap. Heat it up real good and backed it out. Bought a 6mm SS bolt, cut what I needed and screwed it in with some red Locktite. Go back to resetting the caps when "click", the one next door does the same thing. Now you might think, "hey what are you using for a torque wrench?" Answer: brand new $150 Proto 3/8 drive, initialed by half a dozen "calibrators" at the factory.

Anyone else ever have this problem? I'm thinking of replacing all this pot metal crap with SS studs. The cam studs on my Jag were the same size and took a heck of a lot more torque than 80 In lbs.

Bill MacDonald
Redmond, WA

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'03 Aprilia Tuono "Thunder"
'09 K1300S "Rufus II"

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post #2 of 22 Old Mar 25th, 2010, 12:38 am
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Re: Sheared Off Cam Bearing Studs

Quote:
Originally Posted by Hairpin
An interesting twist on an otherwise uneventful, but pleasurable task. I used to do this drill all the time on my '62 Jaguar. Much the same. Imagine my dismay when I am torquing down the bearing caps carefully, 1/4 turn at a time, criss-cross pattern, starting at the middle and working toward the ends when I hear "click". Good, I say, finally reached the torque setting (80 in lbs) according to Clymer. But alas, the nut and the first inch of the stud kerplunk down on my stand. Not good. Thankfully, there's a good 2 inches of stud exposed when I remove the bearing cap. Heat it up real good and backed it out. Bought a 6mm SS bolt, cut what I needed and screwed it in with some red Locktite. Go back to resetting the caps when "click", the one next door does the same thing. Now you might think, "hey what are you using for a torque wrench?" Answer: brand new $150 Proto 3/8 drive, initialed by half a dozen "calibrators" at the factory.

Anyone else ever have this problem? I'm thinking of replacing all this pot metal crap with SS studs. The cam studs on my Jag were the same size and took a heck of a lot more torque than 80 In lbs.
80lbs sounds high. Is the Clymer manual wrong????

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post #3 of 22 Old Mar 25th, 2010, 1:13 am
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Re: Sheared Off Cam Bearing Studs

Quote:
Originally Posted by Ted Shred
80lbs sounds high. Is the Clymer manual wrong????
The BMW manual specifies the camshaft bearing cap torque at 10 NM which is 88.5 in. lbs..


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post #4 of 22 Old Mar 25th, 2010, 2:39 am
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Re: Sheared Off Cam Bearing Studs

Hairpin You may want to reconsider using stainless studs for your cam journals. Stainless has a different expansion rate than steel, resulting in the cam journals being looser at temperature than with the steel studs. Also stainless is not as strong as steel. It is a much softer alloy.
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post #5 of 22 Old Mar 25th, 2010, 3:47 am
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Re: Sheared Off Cam Bearing Studs

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Hairpin You may want to reconsider using stainless studs for your cam journals. Stainless has a different expansion rate than steel, resulting in the cam journals being looser at temperature than with the steel studs. Also stainless is not as strong as steel. It is a much softer alloy.
Yep, SS is weaker than even SAE grade 5, or ISO grade 8.8. Stainless steel fasteners are for corrosion resistance only, NOT strength.

Expansion rate of SS is so close to steel that it will not be an issue.

Something just does not add up here. I have never heard of anyone breaking a cam bearing cap stud. Stripping them out of the head, yes. There should be no way that 10 NM torque would break one. When people have overtightened the valve cover nuts, stripping the studs out has always been the result.

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
Dandridge, TN
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.
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post #6 of 22 Old Mar 25th, 2010, 8:41 am
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Re: Sheared Off Cam Bearing Studs

1 Newton Meter equals .7376 lbs foot so 10 NM = 7.376 Lbs Ft. not 80 Lbs Ft. Are you over tightening? 7.376 is a long way from 80
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post #7 of 22 Old Mar 25th, 2010, 8:55 am
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Re: Sheared Off Cam Bearing Studs

Quote:
Originally Posted by High_Plains_Drifter
1 Newton Meter equals .7376 lbs foot so 10 NM = 7.376 Lbs Ft. not 80 Lbs Ft. Are you over tightening? 7.376 is a long way from 80
they're talking 80 inch pounds - not foot pounds ...... but I would be suspicious of using the wrong scale on the torque wrench.

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post #8 of 22 Old Mar 25th, 2010, 12:28 pm Thread Starter
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Smile Re: Sheared Off Cam Bearing Studs

Nope, triple checked the scale on the torque wrench. I suspect these were overtightened/stressed at the last adjustment prior to my ownership 3 years and 20k miles ago. Looking at the positive, I am grateful that it's apart and on my stand when this happens rather than going down the road in eastern Montana when they break. You'd be kinda shocked at how easy these let go. Thankfully they're breaking just inside the caps and not the head. They don't even come close to stripping.

Thank you for the info on SS vs steel. I would not have thought that, given that the stainless eats hacksaw blades at twice the rate of steel. Like I say, the more I learn, the less I know. Maybe not a good idea to introduce a variant and I should replace them with fresh steel.

Thank you kindly for your valuable input.

Bill MacDonald
Redmond, WA

'99 LT "Luther"

'03 Aprilia Tuono "Thunder"
'09 K1300S "Rufus II"

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post #9 of 22 Old Mar 25th, 2010, 2:23 pm
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Re: Sheared Off Cam Bearing Studs

Check an dubble check ??. My 3/8 in Snap-on torque wrench reads in ft lbs, 1/4 in drive one reads in in. lbs. U-TURN
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post #10 of 22 Old Mar 25th, 2010, 4:33 pm
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Re: Sheared Off Cam Bearing Studs

Quote:
Originally Posted by Hairpin
---------------------------------------------------
Thank you for the info on SS vs steel. I would not have thought that, given that the stainless eats hacksaw blades at twice the rate of steel. --------------------------
Stainless steel is made corrosion resistant by the addition of Chromium, along with some other corrosion resistant metals. These are much harder than the base steel, and do wear cutting tools rapidly. The tensile strength of the alloy is much weaker than medium to high strength ally steels though. Where tensile strength is needed, such as these cam bearing cap bolts, the stock alloy steel is MUCH better.

Also, the same torque applied to both a stainless and steel bolt will likely stress the stainless to yield point! That would be a big problem in this application.

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
Dandridge, TN
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.
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post #11 of 22 Old Mar 25th, 2010, 9:46 pm Thread Starter
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Re: Sheared Off Cam Bearing Studs

Can't find the right steel all-thread locally. It would have to be a special order. Called the dealer service tech and he thought the stainless would be fine. Besides, the closest dealer replacement parts are 3 states away, and I didn't want to ask much they would cost. Bought 8 2" stainless bolts, cut off the heads, and they torqued up fine. I'll let you know if they blow up. Many thanks for everyone's input. If it fails, at least I can say I know why and I'll scream "Y'ALL TOLD ME SO!!!"

Bill MacDonald
Redmond, WA

'99 LT "Luther"

'03 Aprilia Tuono "Thunder"
'09 K1300S "Rufus II"

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post #12 of 22 Old Mar 25th, 2010, 10:17 pm
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Re: Sheared Off Cam Bearing Studs

I broke a grade 8, 3/8 diameter bolt in a HD.

Before the chants "Thor, Thor, Thor!" begin, let me tell ya what we found.

When we pulled the bolt from the engine and compared the parts we found a HUGE void, almost like corrosion in the center of the shank, flush with the underside of the bolt head I twisted off..

So, it was a defective bolt... yes, it was marked "China"... surely not an issue... just sayin'... ymmv.

My guess is just a defective "stud"... they are not xrayed or inspected... they are bought in bulk I'll bet...

Ok.. Thor, Thor, Thor!!!
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post #13 of 22 Old Mar 25th, 2010, 10:19 pm
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Re: Sheared Off Cam Bearing Studs

Hairpin..

instead of futzing over finding "all thread", buy a loooong bolt of size and hardness you like.

Take said bolt to a machine shop and ask them to thread it.... then cut to length.
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post #14 of 22 Old Mar 26th, 2010, 6:23 am
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Re: Sheared Off Cam Bearing Studs

Quote:
Originally Posted by cfell
Hairpin..

instead of futzing over finding "all thread", buy a loooong bolt of size and hardness you like.

Take said bolt to a machine shop and ask them to thread it.... then cut to length.
That would work, but just be aware that a thread cut on by a machine shop will not be as strong as the roll formed threads on bolts. Roll formed threads are far more resistant to deformation or stripping, due to the "forging" action to form them. Cut threads cut through the "grain" structure of the steel, and strip and gall far easier, also normally do not have the surface finish of the formed thread whether cut by a die or single point threaded on a lathe.

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
Dandridge, TN
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.
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post #15 of 22 Old Mar 26th, 2010, 2:42 pm
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Re: Sheared Off Cam Bearing Studs

Quote:
Originally Posted by dshealey
Yep, SS is weaker than even SAE grade 5, or ISO grade 8.8. Stainless steel fasteners are for corrosion resistance only, NOT strength.

Expansion rate of SS is so close to steel that it will not be an issue.

Something just does not add up here. I have never heard of anyone breaking a cam bearing cap stud. Stripping them out of the head, yes. There should be no way that 10 NM torque would break one. When people have overtightened the valve cover nuts, stripping the studs out has always been the result.

Correctomundo!! Standard off-the-shelf SS has about a Grade-2 equivalence!! Not good!! There are some stainless fasteners with very high strength, but not ordinarily available!

Listen to dshealey, he knows his sh*t!!
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post #16 of 22 Old Mar 26th, 2010, 2:44 pm
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Re: Sheared Off Cam Bearing Studs

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Originally Posted by Hairpin
Can't find the right steel all-thread locally.
Even all-thread is low strength....UNLESS you specify "B-7" Grade.....
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post #17 of 22 Old Mar 26th, 2010, 3:30 pm
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Re: Sheared Off Cam Bearing Studs

Socket head cap screws are normally at least grade 8 or better. and can be found in "all thread".
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post #18 of 22 Old Mar 26th, 2010, 5:01 pm
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Re: Sheared Off Cam Bearing Studs

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Socket head cap screws are normally at least grade 8 or better. and can be found in "all thread".
When dealing with metric fasteners though, the term "Grade 8" can be very misleading. Normally Grade 8 is the SAE designation for high strength American Inch fasteners. Metric fasteners conform to an entirely different specification, ISO. ISO grade 8.8 is considerably less strong than SAE grade 8, and is more equivalent to ISO grade 10.9. Also, inch socket head fasteners made for the US market almost all conform to grade 8 SAE standard, so it is not likely to get lower grade ones. The metric market however makes socket head fasteners to multiple grades, with ISO 8.8, 10.9, and 12.9 being the more common ones. So, you can get a grade 8.8 metric screw, and have a weaker bolt than a SAE grade 8 inch one. However, with metric you have the option of getting ISO 12.9, which has considerably higher tensile strength than SAE grade 8!

This stuff can be very confusing to anyone not pretty heavily experienced with it.

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
Dandridge, TN
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.
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post #19 of 22 Old Mar 26th, 2010, 5:26 pm
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Re: Sheared Off Cam Bearing Studs

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Originally Posted by dshealey
When dealing with metric fasteners though, the term "Grade 8" can be very misleading. Normally Grade 8 is the SAE designation for high strength American Inch fasteners. Metric fasteners conform to an entirely different specification, ISO. ISO grade 8.8 is considerably less strong than SAE grade 8, and is more equivalent to ISO grade 10.9. Also, inch socket head fasteners made for the US market almost all conform to grade 8 SAE standard, so it is not likely to get lower grade ones. The metric market however makes socket head fasteners to multiple grades, with ISO 8.8, 10.9, and 12.9 being the more common ones. So, you can get a grade 8.8 metric screw, and have a weaker bolt than a SAE grade 8 inch one. However, with metric you have the option of getting ISO 12.9, which has considerably higher tensile strength than SAE grade 8!

This stuff can be very confusing to anyone not pretty heavily experienced with it.
That is why I just said "grade 8". Pretty much everyone knows what "grade 8" means and can equate that to a strong fastener. I wasn't attempting to delve into the actual hardness and strength ratings of metric fasteners.
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post #20 of 22 Old Mar 26th, 2010, 5:30 pm
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Re: Sheared Off Cam Bearing Studs

Have a look here at ARP's catalog
http://www.arp-bolts.com/Catalog/Catalog.html
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post #21 of 22 Old Mar 26th, 2010, 9:09 pm
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Re: Sheared Off Cam Bearing Studs

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That is why I just said "grade 8". Pretty much everyone knows what "grade 8" means and can equate that to a strong fastener. I wasn't attempting to delve into the actual hardness and strength ratings of metric fasteners.
The problem is that it is very difficult to find metric fasteners in SAE grade 8. HoloKrome and Camcar make them, as they are US based manufacturers, but the great majority of metric fastener manufacturers adhere to ISO standards, so it is important for anyone purchasing metric fasteners for strength to know that ISO grade 8.8 is NOT equivalent to SAE grade 8. You have to get ISO grade 10.9 to be roughly equivalent.

Point for knowledge: Most of the socket head set screws on the LT are ISO grade 8.8. Unfortunately, recommended torques on the M6 ones is near 10NM, which is very near the yield point of an M6. That is why so many oil filter cover screws have had the heads snapped off! That is why I have sold so many sets of ISO grade 10.9 replacements for them. Very little room for error with the 8.8's, torque wrenches highly recommended here. Takes very little over torque to break them, as way too many have found out.

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
Dandridge, TN
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.
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post #22 of 22 Old Mar 26th, 2010, 11:39 pm
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Re: Sheared Off Cam Bearing Studs

Quote:
Originally Posted by dshealey
The problem is that it is very difficult to find metric fasteners in SAE grade 8. HoloKrome and Camcar make them, as they are US based manufacturers, but the great majority of metric fastener manufacturers adhere to ISO standards, so it is important for anyone purchasing metric fasteners for strength to know that ISO grade 8.8 is NOT equivalent to SAE grade 8. You have to get ISO grade 10.9 to be roughly equivalent.

Point for knowledge: Most of the socket head set screws on the LT are ISO grade 8.8. Unfortunately, recommended torques on the M6 ones is near 10NM, which is very near the yield point of an M6. That is why so many oil filter cover screws have had the heads snapped off! That is why I have sold so many sets of ISO grade 10.9 replacements for them. Very little room for error with the 8.8's, torque wrenches highly recommended here. Takes very little over torque to break them, as way too many have found out.
Torque wrench? On those little fasteners? Nah. Run them down till they bottom then snug em up.
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