Anything special about the 12 point bolts for the timing gear?

Rattlenbang

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I worked too long and too late today and ended screwing up. Replaced the injection pump and got everything together, lines bled and finally got it started. Ran great but started making intermittent ticking noise. then a loud clacking. Shut it off right away, and immediately knew my mistake. I had hand screwed in the drive gear nuts (I told myself not to put them in until I was ready to tighten them, but ignored myself) but forgot to tighten then, and all three came out. Fortunately the gear stayed on the pump, but the bolts are mangled.

Other than being 12 point, does anyone know if there's anything special about them? One bolt head not mangled says FC on it, but that's not a hardness code. Are they specially hardened bolts or what? Somebody on ebay wants 30 bucks for a set but I need them sooner rather than later.
 

chillman88

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I think Russ @typ4 said you can use the bolts that come in some specific u-joint strap kit. I don't recall which one, maybe he'll chime in.
 

typ4

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If you have time for shipping I have new bolt kits for those.
 

Rattlenbang

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If you have time for shipping I have new bolt kits for those.
I'd need it by tomorrow, so that's not in the cards, but thanks.

According to the above link, it seems they are designed to allow tighter torquing. I'd guess that the required 25 ft-lbs on an ordinary hex 5/16 fastener would be excessive, although that says nothing about bolt hardness, just how the head shape allows higher torque.
 

typ4

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The 12-point bolts are grade 12 that's why they can take the higher torque.
 

ShadetreeV

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Just throwing my 2 cents in.
12 point (aka. ferry cap screws) are closer
to grade 9 (180,000psi tensile). Not the same a s a run of the mill grade 8 (150,000psi)
Aircraft/mil spec is a whole different animal as well if you're into reading up on those sorts of things
So . Yes these bolts are special.
 

Thewespaul

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Yes they are special. Run new u joint strap bolts (similar but not the same hardening) and get the install kit from Russ with the stanadyne bolts to install later.
 

IDIBRONCO

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I'd guess that the required 25 ft-lbs on an ordinary hex 5/16 fastener would be excessive, although that says nothing about bolt hardness, just how the head shape allows higher torque.
This is erroneous thinking. The bolt size is not from the bolt head itself. The size of bolts is the size of the threads. So these are not 5/16" bolts. They are smaller and, judging from the fact that the bolts from a bolt and strap kit for a rear u-joint will work, I'm guessing that they are metric.
 

ifrythings

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Another option also

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Rattlenbang

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Well, I found the grade 8 bolts and popped them with no problems, with a dab of locktite. But I sure wonder about the engineering and specificity of the fasteners; the driving gear has a steel dowel right into the pump drive and 3 of these hardened suckers to hold it into place. I know the injectors pop at about 2000psi, but I'm surprised that it would translate into such a mechanical load on the bolts. Other diesels I've worked on with Bosch VE pumps use a single ordinary automotive grade 3/8" bolt on a pulley driven by a rubber belt.
 
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