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Kind of a basic question, but I've never wrenched on a BBC before. What is the proper torque for the 1/2 inch fine thread grade 8 bolt holding on my harmonic balancer?
 

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With/without

Kind of a basic question, but I've never wrenched on a BBC before. What is the proper torque for the 1/2 inch fine thread grade 8 bolt holding on my harmonic balancer?
With or without thread lube?.....I just take it as tight a 1/2" impact will get it before it starts to really hammer. Not critical IMO because of the press fit to the crank..........Ray
 

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With or without thread lube?.....I just take it as tight a 1/2" impact will get it before it starts to really hammer. Not critical IMO because of the press fit to the crank..........Ray
Gotta respectfully dissagree with that Ray!

The world revolves around clamp load!

Use the best bolt you can, with the proper lube torqued to manufactures specs!!

FYI, Damper to snout interference should be no less than .0005 and no more than .001. Lube both snout and damper hub when installing! Anything less than .0005 needs allot of clamp load to properly support. Any more than .001 is not needed, and could cause problem by not properly seating the damper against the gear/crank step due to giving a false sense of it being tight.
I know allot of people get away with a bigger range than this, but if we are talking about it, we might as well mention best case!
 

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Gotta respectfully dissagree with that Ray!

The world revolves around clamp load!

Use the best bolt you can, with the proper lube torqued to manufactures specs!!

Any more than .001 is not needed, and could cause problem by not properly seating the damper against the gear/crank step due to giving a false sense of it being tight.
]/QUOTE]

This a biggy. Specially with ATI dampers and aftermarket cranks. I always check the damper on the crank before installing the crank just to make certain the damper goes all the way to the timing gear.



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Bottoming out

Gotta respectfully dissagree with that Ray!

The world revolves around clamp load!

Use the best bolt you can, with the proper lube torqued to manufactures specs!!

Any more than .001 is not needed, and could cause problem by not properly seating the damper against the gear/crank step due to giving a false sense of it being tight.
]/QUOTE]

This a biggy. Specially with ATI dampers and aftermarket cranks. I always check the damper on the crank before installing the crank just to make certain the damper goes all the way to the timing gear.
Gotta respectfully dissagree with that Ray!

The world revolves around clamp load!

Use the best bolt you can, with the proper lube torqued to manufactures specs!!

FYI, Damper to snout interference should be no less than .0005 and no more than .001. Lube both snout and damper hub when installing! Anything less than .0005 needs allot of clamp load to properly support. Any more than .001 is not needed, and could cause problem by not properly seating the damper against the gear/crank step due to giving a false sense of it being tight.
I know allot of people get away with a bigger range than this, but if we are talking about it, we might as well mention best case!
With the pan off there is little doubt about the drive flange and/or damper being bottomed against the lower gear. I install the drive flange before snugging the t/cover to ensure the sealing surface is centered in the seal. And yes, there are dowels, not the factory dowels, to locate it, but I still like to be sure. I hate oil leaks. The aftermarket parts make this even more important. Some aftermarket cranks are "big", some aftermarket dampers/drive flanges small, and need to be carefully honed to size. .0005/.001 is pretty damn tight unless temperature variance is used, ie heating the flange in the Az sun for an afternoon.....I'm not saying "Don't torque it".....But 85lbs may bottom it out in one instance, but not another. And then there are the installation tools. Do they guarantee the part is bottomed correctly? In reality, a 1/2" fine thread, lubed, and hit with a decent impact, probably exceeds the 85 lbs
torque. I've only seen one come off, and it was a SBC that wasn't even threaded!!!!........Ray
 

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With the pan off there is little doubt about the drive flange and/or damper being bottomed against the lower gear. I install the drive flange before snugging the t/cover to ensure the sealing surface is centered in the seal. And yes, there are dowels, not the factory dowels, to locate it, but I still like to be sure. I hate oil leaks. The aftermarket parts make this even more important. Some aftermarket cranks are "big", some aftermarket dampers/drive flanges small, and need to be carefully honed to size. .0005/.001 is pretty damn tight unless temperature variance is used, ie heating the flange in the Az sun for an afternoon.....I'm not saying "Don't torque it".....But 85lbs may bottom it out in one instance, but not another. And then there are the installation tools. Do they guarantee the part is bottomed correctly? In reality, a 1/2" fine thread, lubed, and hit with a decent impact, probably exceeds the 85 lbs
torque. I've only seen one come off, and it was a SBC that wasn't even threaded!!!!........Ray
No problem Ray.

Just hit it with an impact wrench! :)sphss

Do you do your rods and mains like that too???? LOL

Never mind......no need to answer that! :D
 

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Bbc

Grade 8 cranskshaft bolt should hold 120 ftlbs. If you don't get them tight, they will loosen. Detonation will loosen them. Make sure the bolt catches at least 3/4 inch of threads.
I torque my hemi crank bolt to 400 ftlbs. 3/4 grade 9 bolt, any less and they'll loosen up.
Good luck
 

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P.S. I recently put on a trick 12-point bolt that had 95 ft-lb load in my forged steel crank, but also torque, moly or oil offers different torque spec...I too used to hit it with the impact, but a 3/8" impact won't get you there, 1/2" drive impact with some DFMs will. ARP recc'd that torque spec using moly is lower than oil.
 

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torque

Do you have any specs on that bad boy.;)
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Google grade 8 bolt torque, you'll see about 119 ftlbs.
Everytime I pulled down my hemi the crankshaft bolt was loose. The hubs were getting wrecked, loosened were the interferance was going away. I was going to buy my next crank with a splined snout. I talked to Henry Valasco (Valasco Crankshaft Co.) he told me to call Automan and buy his bolt (grade 9). Bob Otto (automan) told me to torque his bolt to 400 ftlbs. I haven't had a problem since. Detenation kills the snout and loosens the bolt. BBC don't have a 3/4 bolt, I would max the 1/2 bolt. This what I've learned from spending too much money. Good Luck
Glenn
 

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Grade 9 bolts

Try Bob at Automan Technologies 530-885-8815, if you get him on a good day, he'll talk forever. That isn't bad bad,veryknowedgeable.
automantechnologies.com
 
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