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Drilling and tapping a block for bigger head fasteners...

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  • Guido
    replied
    The larger the firecracker, the higher the tin can goes.

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  • Paul Alciatore
    replied
    I wasn't joking. It sounds to me like you are going a fair amount beyond the known good envelope and a catastrophic failure is a definite possibility.

    I mean, I am sure the original engineers who designed this engine were under the well known restraints of performance vs. cost. I am sure they included or at least thought they included a certain safety factor. But you are shaving away some of that factor so now it is reduced or perhaps even non existent. Now, add one small defect in the casting, near one of your new studs/bolts. A void, an inclusion, a small crack, whatever. The original safety margin would have taken care of it. But now ..... shrapnel?

    I'm just saying to use some care.

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  • RacinNdrummin
    replied
    Originally posted by Paul Alciatore View Post
    Don't forget the shrapnel shield.
    Lol, its not out of the realm of structure of this platform..... At least yet....This will set the ceiling, or set a new benchmark, one of the two.

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  • RacinNdrummin
    replied
    Originally posted by strokersix View Post
    As you say, more clamp force is required to withstand the applied loading. However: Did you study joint diagrams? Increasing fastener diameter should be accompanied by increased fastener length for a robust connection. If you have room, stout hardened standoff bushings (like 1 inch tall) to increase fastener stretch would help a lot. If there is enough meat in the bottom of the block you may be able to counterbore and tap deeper to increase the fastener grip length (and amount of stretch) as well.

    If you don't believe or understand what I'm trying to tell you, boltscience.com has some good basic info.
    I understand what you are saying but I simply don't have the room. I tried drilling the test block .875" deeper (7.000" studs vs. 6.125" studs, 7" is how long the 7.3 studs are) and I got a broken boss because the casting necks down at that point. Also, the rocker arms are directly over the top of certain studs, so I am limited by how much I can space the nuts up as well.

    Literally the only way of achieving the clamp load I want is using these studs, I have already done a bunch of experimenting, the stud isn't the issue, its the meat to hold it in place. 8740 190Kpsi studs have the right amount of clamp load I need.

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  • Paul Alciatore
    replied
    Don't forget the shrapnel shield.



    Originally posted by RacinNdrummin View Post
    350cc of fuel to 4000rpm

    ~105lb/min of Airflow

    ~50psi of boost pressure

    Shooting for 600-700 horsepower at the wheels with a 3400rpm horsepower peak, and about 1300lb-ft of torque at 2600RPM...

    8 cylinder Bosch P7100 injection pump
    16:1 compression
    94 IDIT connecting rods
    Main Girdle/Studs
    BW 60/68/.91 and 75/96/1.32 Turbochargers
    Block Deck will be O-ringed

    Leave a comment:


  • strokersix
    replied
    Originally posted by RacinNdrummin View Post
    Already been down that road. I tested the 7/16" and 1/2" fasteners to yield. 125ft/lbs of torque on the 7/16" studs before reaching yield (I lifted a head with these at half the fueling I am going to be running), 1/2" stud was 180ft/lbs before yield, and while that's right about what I am going to need for clamping load, If I am going to be drilling and tapping anyway, 9/16" are more stable in that range. Plan was to take to 200ft/lb's on the 9/16 studs. Im not worried about block structure other than lateral load on the thread bosses, the rest of the block is stout enough to take it, and the bolt bosses are tied into the bottom of the block, not the cylinder walls.
    As you say, more clamp force is required to withstand the applied loading. However: Did you study joint diagrams? Increasing fastener diameter should be accompanied by increased fastener length for a robust connection. If you have room, stout hardened standoff bushings (like 1 inch tall) to increase fastener stretch would help a lot. If there is enough meat in the bottom of the block you may be able to counterbore and tap deeper to increase the fastener grip length (and amount of stretch) as well.

    If you don't believe or understand what I'm trying to tell you, boltscience.com has some good basic info.

    Leave a comment:


  • Ironwoodsmith
    replied
    Your'e going to need a bigger boat!

    Leave a comment:


  • RacinNdrummin
    replied
    Originally posted by Bob Fisher View Post
    If you would not mind, what are you doing with a 6.9 Diesel engine that requires that much clamping force? Bob.
    350cc of fuel to 4000rpm

    ~105lb/min of Airflow

    ~50psi of boost pressure

    Shooting for 600-700 horsepower at the wheels with a 3400rpm horsepower peak, and about 1300lb-ft of torque at 2600RPM...

    8 cylinder Bosch P7100 injection pump
    16:1 compression
    94 IDIT connecting rods
    Main Girdle/Studs
    BW 60/68/.91 and 75/96/1.32 Turbochargers
    Block Deck will be O-ringed
    Last edited by RacinNdrummin; 10-22-2014, 09:36 PM.

    Leave a comment:


  • andywander
    replied
    PS it's ft-lbs or foot pounds, NOT feet per pound or ft/lb as you have written.

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  • Bob Fisher
    replied
    If you would not mind, what are you doing with a 6.9 Diesel engine that requires that much clamping force? Bob.

    Leave a comment:


  • RacinNdrummin
    replied
    The reason I didn't go with ARP+625's or something is that ARP wanted $1300 for a set of them. Being that a 7/16 +625 stud at 285Kpsi is still less than a 9/16" 190Kpsi 8740 stud, Id rather spend $400 on a set of those, and drill/tap the block.

    Leave a comment:


  • RacinNdrummin
    replied
    Originally posted by strokersix View Post
    You may already know this but in case you don't: Increasing fastener diameter is often the wrong choice when faced with a joint durability problem. Joint durability under service loads depends on fastener stretch and the relative stiffness of the parts compared to the fastener. Larger diameter fasteners change the relative stiffness in the wrong direction in terms of durability. Do some reading on bolted joint diagrams. boltscience.com is one source of information.

    Best choice, if available, is higher grade fasteners (studs or bolts) of the same diameter. If you are going to increase fastener diameter, consider making custom hardened standoff bushings so you can use longer fasteners for more stretch.

    Once you have chosen your fastener and modified the parts, I suggest testing the torque/tension relationship on the real parts. Get some extra fasteners. Measure length, torque, then remove and measure length again. Repeat, upping the torque each time until you achive yield, say .002 inch permanent stretch. Now you know what torque value to use, say 80% of the value that produced .002 yield.

    Post back here with questions if you wish.
    Already been down that road. I tested the 7/16" and 1/2" fasteners to yield. 125ft/lbs of torque on the 7/16" studs before reaching yield (I lifted a head with these at half the fueling I am going to be running), 1/2" stud was 180ft/lbs before yield, and while that's right about what I am going to need for clamping load, If I am going to be drilling and tapping anyway, 9/16" are more stable in that range. Plan was to take to 200ft/lb's on the 9/16 studs. Im not worried about block structure other than lateral load on the thread bosses, the rest of the block is stout enough to take it, and the bolt bosses are tied into the bottom of the block, not the cylinder walls.

    Leave a comment:


  • RacinNdrummin
    replied
    Originally posted by Doozer View Post
    Are you torquing the studs into the block? That is never the right thing to do.
    Or do you mean you are torquing the nuts on the studs at assembly?

    -D
    This is the torque of the nut on the stud. Studs are installed finger tight and backed off a half turn.

    Leave a comment:


  • RacinNdrummin
    replied
    Originally posted by Joe Rogers View Post
    If it is worth upgrading the fasteners for durability why don't you install studs?
    Joe
    The 9/16 fasteners are 190,000psi ARP studs.

    Leave a comment:


  • RacinNdrummin
    replied
    Originally posted by Toolguy View Post
    Maybe 1/2" bolts would be safer?
    1/2" 190,000psi studs don't have the clamping load necessary for what I am going after. I have tested a 1/2" stud, and the thread interference isn't an issue, so physically it would work, but like I said, its just not enough for the application.

    Leave a comment:

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