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07-15-2020, 11:03 PM
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#1 |
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Registered User
 Join Date: Dec 2018
Location: Carnation, WA.
Posts: 258
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Grade 8 Bolts
Should I put Grade 8s::::::
Clamshell Mounts to Frame Mounts to Engine Bellhousing Etc. Etc. |
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07-15-2020, 11:06 PM
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#2 |
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Registered User
Join Date: Jan 2013
Location: Eastern TN
Posts: 1,919
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Re: Grade 8 Bolts
I reuse what it came with. If replacing then grade 8s except specialty bolts like starter bolts. Those are factory style replacements. Anything less than 8s is reserved for tractor shear bolts.
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07-15-2020, 11:54 PM
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#3 |
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Registered User
Join Date: Oct 2016
Location: Dallas Texas
Posts: 2,879
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Re: Grade 8 Bolts
.
Yes... G8, where necessary! Before I became fully aware of the various grades, I used whatever was available... -klb
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67 C10 fleet fuel injected '70 402, 700r4, 3.73 posi 07 335 sport turbo 6sp 94 Trans Am GT LT1 6sp posi -- sold after 22yrs 99 540 sport V8 6sp -- sold 73 240z L24 4sp -- given to friend 68 C10 step 350/350 3.73 open -- sold |
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07-16-2020, 01:03 AM
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#4 |
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Registered User
Join Date: May 2013
Location: Post Falls, ID
Posts: 884
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Re: Grade 8 Bolts
Grade 5 should be fine for motor mounts. I have seen a lot of motor mounts bolted down with grade 5 hardware. I have never seen grade 5 fail in that application.
That being said, I recommend using Grade 8 Bolts. The rule of thumb here is this – if it breaks, could someone die? If the answer is yes, then use a Grade 8 fastener, period. |
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07-16-2020, 01:06 AM
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#5 |
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Registered User
Join Date: Feb 2013
Location: central California
Posts: 2,727
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Re: Grade 8 Bolts
This quick read explains why grade 8 is nearly always the better choice https://rtstools.com/are-grade-8-bol...s-10-9-metric/
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07-16-2020, 01:58 PM
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#6 | |
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Registered User
Join Date: Jan 2007
Location: Puyallup, WA
Posts: 1,661
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Re: Grade 8 Bolts
Quote:
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72 C10 lwb fleetside -stock 350/350 combo |
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07-16-2020, 09:55 PM
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#7 |
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Senior Member
Join Date: Jan 2001
Location: Orem, Utah
Posts: 7,798
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Re: Grade 8 Bolts
I fought my new motor mounts(72 Blazer, Anchor brand mounts) trying to tighten the bolt that goes through the towers. It just kept spinning, so I finally pulled one of the mounts out and checked the threads. It turned out they were threaded for M10-1.5 bolts. All the other bolts on the mounts and perches are grade 8.
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I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson |
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07-16-2020, 10:36 PM
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#8 |
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Registered User
Join Date: Jun 2015
Location: Carlos MN
Posts: 1,923
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Re: Grade 8 Bolts
I buy my grade 8 bolts at Fleet Farm in bulk. To make the resto look better all the body under frame bolts are grade 8. 1/4" up to 1/2" suspension bolts. They are kind of gold in color and are so much per pound.
In regards to metric bolts they typically are marked on the head 10.9? so it's a metric bolt. |
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07-20-2020, 10:42 AM
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#9 |
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Registered User
Join Date: Mar 2011
Location: MA
Posts: 353
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Re: Grade 8 Bolts
I think there is a lot of belief in using grade 8 bolts are better. Yes they are stronger but usually not needed for most applications. Steering components? Yes I'd use grade 8. Everything else? Grade 5 is fine. Years ago, maybe still the case, Mack Truck only uses Grade 8 on steering. The rest is grade 5. Some applications you want a 5 in there as the 8 will break. Where as the 5 will bent before it breaks giving some warning. Now I'm not a Rockwell hardness expert by any means but if you look at the strengths on each bolt. The numbers are crazy high. Usually when bolts break they wear first tot the point of failure. I also wouldn't use a grade 8 bolt in a blind hole. Drilling them out isn't fun.
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