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  #1  
Old Dec 4th, 09, 07:49 PM
Black Z Black Z is offline
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Default Torque Converter Bolts

I purchased a B&M holeshot 2400 torque converter for my TH350 that came today. I had picked up some ARP converter bolts in 3/8-24 assuming that was the correct size, I was wrong. It came will 3/8-16 bolt, but they are only grade five. ARP does not have a 3/8-18 converter bolt so I was wondering what would be the next best thing? Should I just get some grade 8 bolts from the hardware store? Will the head on a normal grade 8 bolt stick up to far, the ARP bolts have a shorter head? Thanks
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Last edited by Black Z; Dec 4th, 09 at 08:13 PM.
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Old Dec 4th, 09, 09:53 PM
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Everett#2390 Everett#2390 is offline
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Default Re: Torque Converter Bolts

Grade 5 will be just fine.
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Old Dec 4th, 09, 09:56 PM
Black Z Black Z is offline
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Default Re: Torque Converter Bolts

I have heard several stories of grade five bolts shearing off, I do not want to take that chance over a few bolts. I at least want grade 8, just want to make sure the heads will clear.
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Old Dec 5th, 09, 07:47 AM
icpop icpop is offline
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Default Re: Torque Converter Bolts

Actually if you research fastener hardware you should see discussion on shear strength vs pull or clamping strength. I believe the grade 8 are better for clamping applications vs shear load application (torque converter) It has something to do with the hardness of the fastener. check it out good luck
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Old Dec 5th, 09, 09:08 AM
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Default Re: Torque Converter Bolts

I bought a set for a TH350 off the HELP isle at the parts store.
Hope they're good enough. There's no grade markings on them.
If you're worried, get them over the counter at the parts store.
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  #6  
Old Dec 5th, 09, 10:01 AM
TJS69 TJS69 is offline
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Smile Re: Torque Converter Bolts

Hardened steel is tough to wear resistance, but it is brittle. A non-hardened bolt CAN be stronger. It all depends on useage. A torque converter bolt that is hit hard, at lets say a drag strip can easily snap. Now lets say on a road course - more constant stress on the bolt a heat treated bolt may work well. I vote for the grade 5 bolt as it is kind of in between a hardened bolt and a non-hardened.
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Old Dec 5th, 09, 01:18 PM
DOUG G DOUG G is offline
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Default Re: Torque Converter Bolts

As a grade 8 will have 190,000 (?) tensile strength (straight pull) and a grade 5 at 120,000 (?) yet when side loaded the grade 8 will break where the 5 will bend first.

We have 20" screws moving tons of rock 24-7 and use grade 3's to 5's.
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Old Dec 5th, 09, 02:01 PM
srode srode is offline
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Default Re: Torque Converter Bolts

My understanding is the idea of the higher grade fastener is to utilize the increased clamping pressure to hold the parts together and eliminate movement between the parts not rely on the bolt's sheer strength. The higher grade fastener must be tightened to the correct torque spec to achieve the higher clamping pressure - Grade 8 torque spec is about 50% higher than the Grade 5 and so is the clamping force when torqued to spec. I don't think a bolt in this application is intended to be a shear pin, although in some applications they are to protect more expensive parts and prevent extended downtime. We have some applications at work where this is exactly the case on machine drive couplings.
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Old Dec 5th, 09, 02:25 PM
Fred Ficarra Fred Ficarra is offline
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Default Re: Torque Converter Bolts

Let me go check my COPO torque converter bolts. Be right back,,,
Grade 8. There's six on mine. But my Super Street Fighter only uses 3 grade 5's. (35 pounds torque) Go figure?
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Old Dec 5th, 09, 03:33 PM
srode srode is offline
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Default Re: Torque Converter Bolts

Well the grade of the nut or threaded material has to match the grade of the bolt or you will end up with a stripped nut
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Old Dec 5th, 09, 06:53 PM
jeremycam jeremycam is offline
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Default Re: Torque Converter Bolts

grade 5 is fine. the bolt doesnt take all that much friction. if its tightened, than its doing its job. if seriously in doubt, use grade 8. theyre more than enought to do the job.
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Old Dec 6th, 09, 01:29 AM
BlackoutSteve BlackoutSteve is offline
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Default Re: Torque Converter Bolts

Quote:
Originally Posted by DOUG G View Post
As a grade 8 will have 190,000 (?) tensile strength (straight pull) and a grade 5 at 120,000 (?) yet when side loaded the grade 8 will break where the 5 will bend first.

We have 20" screws moving tons of rock 24-7 and use grade 3's to 5's.
Grade 3? are you sure? Are you reading 3 radial markings on the head as a grade 3? There is no such thing as a grade 3.

As for grade 5 bending before breaking.. In a shear application (which this is), there won't be any bending of the bolts prior to failure. A grade 5 bolt will simply shear under less load than a grade 8. A grade 8 is superior (150,000psi), yet may not be required depending on the amount of loading.
OE Powerglide and TH350 are 3/8-24 Gr5. (GM 3799830) However, Ford use larger 7/16-20 Gr8 in the same application, so "overkill" is not really matter here. Just make sure you torque according to both diameter and grade.

Quote:
Originally Posted by Fred Ficarra View Post
Let me go check my COPO torque converter bolts. Be right back,,,
Grade 8. There's six on mine. But my Super Street Fighter only uses 3 grade 5's. (35 pounds torque) Go figure?
Fred, the amount of torque used to preload the bolt has nothing to do with it's shear strength. The shear strength of a 3/8 Gr5 is still ~7700lbs per bolt (plus ~5" of leverage they have over the crank centerline. Basically, it's a lot! )
Being such a short fastener, the type of bolts used in this application are "place bolts" that use the head of the bolt to apply most of the preload when torquing.
You will note that these bolts have radial slots in the heads or like ARP, have dimples in the center.
These slots and dimples are to allow the head of the bolt to flex at a specified torque (35ft/lbs in your example) for bolt retention.
These bolts are really too large in diameter and too short in length to stretch properly.

http://www.rockcrawler.com/techrepor...ners/index.asp
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Last edited by BlackoutSteve; Dec 6th, 09 at 01:48 AM.
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  #13  
Old Dec 6th, 09, 11:47 AM
Fred Ficarra Fred Ficarra is offline
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Default Re: Torque Converter Bolts

Yep, very big heads. Kinda like some people I know.
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One owner 69 Camaro,(yep, bought it new)
RS SS Hugger Orange, L88, 4:10's tru-tack posi, ducted hood, Endura, spoilers.
TH400 (CX) with Coan 8" converter, GV-OD, 8 track still on console and best et 10.495, 128.79mph 1.428 60'
All with 1960's stuff. (except tires and converter)
+ MT Super Scavenger headers & 3" full exhaust with X pipe.
1000cfm AED and HD Harold-Lunati SR, 725 lift with shaft rockers too.
http://epitomesrebuild.com/
http://ss427.net/
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