Little confusing what you just posted but you are only supposed to finger tighten studs in the block. Some have tried backing the stud out a half turn. Not sure if that's the fix or not tho
Cracked blocks
- Thread starter White_monster
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Little confusing what you just posted but you are only supposed to finger tighten studs in the block. Some have tried backing the stud out a half turn. Not sure if that's the fix or not tho
webb06
Active member
It really doesn't matter if the studs are torqued or not. They are going to want to pull out not apply a pressure down on to the block.
6.4psd916
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I had close to 50 passes on Matt's race and all stock hardware, everything going good, put a 72mm in and lost the gaskets and tc slip was 400rpm at the end of the second pass with the 72mm. With the slip and gasket failure, mph put me just above 650.
bjmunderwater
New member
Ok ive been following this for a bit now and have had a few ideas. The whole reasons for installation of head studs , increased clamping force to resist the increased cyclinder pressures correct? But what is failing first is it the bolts that are stretching and there for decreasing their ability to hold pressure or is it the gasket material failing. But anyway common practice install studs that have increased torque value and puts lets say 70% yeild on the stud = very strong and tight seal but have been cracking block in the same known location, now is the increase in torque value even nessary? Besides from the manufacturers of the stud . Is the stock torque enough to hold the increased pressures if the bolt didnt stretch ? Could one just upgrade the headbolts to a theoretical stronger bolt less prone to streaching like grade6 to grade 10 sotra of thing and use the stock torque value putting less stress on the block?
webb06
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Good thought. Seems logical
Tree Trimmer
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every bolt/stud is designed to stretch. it's only a couple thousandth's, but it stretches.
the tty bolts, the yield is when it stretches. you throw those away, because when they stretch, their junk for re-use.
to put a "stock" amount of tq on a aftermarket stud, will not give you the same clamping force as a tty bolt, as materials are different.
all tq values, along with the lube provided/used, is designed to either stretch that bolt/stud that right amount, or get you right to that point.
to use a lesser amount is pointless and won't get you anywhere, except failing faster, as there is not a adequate amount of tq to hold everything tight.
when your tightening your trailer ball on your hitch, are you going to really crank on the nut because your supposed to, or are you just going snug it up, cuz your concerned about a tq value??
and, in general, upping the "grade" of the bolt, will require a HIGHER tq value, to achieve the proper clamping force. the higher grade bolt will allow the higher tq value before breaking, this is why it higher grade.
the tty bolts, the yield is when it stretches. you throw those away, because when they stretch, their junk for re-use.
to put a "stock" amount of tq on a aftermarket stud, will not give you the same clamping force as a tty bolt, as materials are different.
all tq values, along with the lube provided/used, is designed to either stretch that bolt/stud that right amount, or get you right to that point.
to use a lesser amount is pointless and won't get you anywhere, except failing faster, as there is not a adequate amount of tq to hold everything tight.
when your tightening your trailer ball on your hitch, are you going to really crank on the nut because your supposed to, or are you just going snug it up, cuz your concerned about a tq value??
and, in general, upping the "grade" of the bolt, will require a HIGHER tq value, to achieve the proper clamping force. the higher grade bolt will allow the higher tq value before breaking, this is why it higher grade.
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bjmunderwater
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Ok so with that in mind its not that head bolts are stretching and causing the failure, its just the plain lack of force need to withstand increased cyclinder pressure?
sootie
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huh? its the fact that properly torqued head studs require more torque than the stock tty bolts and some blocks are cracking when head studs are installed.
6.4psd916
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It would be the increased clamping force, not the torque. The torque is what's needed to get that force and is dependent on thread pitch of the stud and stretch of the stud. I believe a flatter pitch thread requires less torque to get the same clamping force.(has something to do why elite and ARP #'s are so different). Some one please correct me if my thinking is incorrect.
griz700rocket
Member
This was my thinking too. What is the thread difference from stock bolts (bottom of bolt) to aftermarket studs (top of stud) and the associated torque values? Anyone had a gasket fail on aftermarket studs? Maybe the manufacturers have over stated torque values?
Can someone expand on Tree Trimmers concept of higher grade bolts needing more torque to achieve the same clamping force. To me a higher grade bolt that will stretch less will not need as much torque because it will stretch less under load.
BBottoms
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Bolt stretch is a factor, but doesn't have a lot to do with clamping force. Higher strength bolts/studs simply let you apply more torque which translates into a higher clamping load. More torque and more clamping force equals increased stress on the threads in the block, regardless of the material of the stud. It's possible that you could back off the torque some, and therefore the clamping force, with studs and still achieve a better than OEM clamp and seal. With the factory bolt size, thread pitch, grade and torque value we should be able to calculate the clamping force. We could then do the same with the head stud and figure what an equivalent OEM clamping load would be at a specific torque value.
BBottoms
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A reference table, although in SAE sizes. Gives and idea of torque value versus clamping load for various grades of bolts.
http://www.spaenaur.com/pdf/sectionD/D48.pdf
http://www.spaenaur.com/pdf/sectionD/D48.pdf
griz700rocket
Member
Don't forget lube makes a difference too. Now to find someone with the knowledge to do this.
BBottoms
New member
I can dig up all the equations, and I do have a degree in engineering, so it's not out of my realm. :gun:
All I really need is the size/pitch/material/torque values for the TTY yield bolts and the various studs and it should be pretty straight forward to make a table with the various clamping loads with different combinations. I'm sure someone, somewhere has already put this together (ARP) but I doubt they will share.
Derek@Vision Diesel
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Seen many late 08s fail? Job 3 trucks?
Seems like its narrowed to a job 1 job 2 deal....seeing it more and more lately
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Strokin6.4
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People have seen '10 blocks crack as well...
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Morgan@Midwest Diesel & Auto
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Yep have a cracked '10 here and a 09.
Meniacal_Mark
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I think it was a matter of quality control more than when it was made.
