Just hardware grade

[71CHEVYSHORTBED402]

I tore down what was primarily an "unmolested" 1971 C-10, and was curious to see how much of the truck was built with GR 8 hardware, which really wasn't much. I'd already recorded all the hardware used, so this didn't take much effort. Doesn't mean they were all built the same.

Other than exceptions for GR 8, these were built with GR 5 hardware. At least I believe so. Much of the #8, #10 & 1/4" hardware is unmarked, but you can bet it's heavier than standard GR 2. So for what worth, here's what I found with GR 8.

Excludes internal components, unless otherwise included.

Excludes head bolts, which are often marked “M” for what worth. What’s an “M” bolt’s gauge, anyone? 80/20 they’re GR8ish.

Can’t speak for upper motor mount or transmission mount bolts. Excludes where the factory punched rivets.

Strikes me U-bolts & lug studs would be GR 8. Perhaps the stainless bumper bolts are GR 8.

______________________________________________________________________________________________

• The transmission crossmember mounts to the frame rails with eight (GR 8) 9/16" hex bolts, hex nuts and split washers

• The engine crossmember mounts to the frame rail bottoms with six (GR 8) 3/4" hex bolts and hex nuts, and 12 flat washers

• The engine crossmember mounts to the frame rail walls using the fixed nuts in the upper control arm brackets and four (GR 8) 5/8" hex bolts, flat washers and split washers

• The upper control arm bracket tops secure to the frame rails with four (GR 8) 5/8" hex bolts

• The harmonic balancer was secured with one (GR 8) 3/4” hex bolt

• The oil pump mounts to the platform with one (GR 8) 5/8” hex bolt.

• The oil drain plug is a specific (GR 8) 9/16” hex flange bolt

• Each motor mount bracket secures to the engine crossmember and frame rail tops with three (GR 8) 9/16” hex bolts.

• The flex plate mounts to the crank’s flange with six (GR 8) 11/16” hex bolts and star lock washers

• The RH exhaust manifold’s 2nd and 3rd holes from the front take two (GR 8) 3/8-16 x 1.1/2” hex flange head bolts, for installing the compressor support rod bracket. The balance of hardware for mounting the exhaust manifolds is 12 (GR 8) 9/16” hex flange bolts.

• The shift control bracket mounts to the LH frame rail’s inner wall using the two holes located immediately in front of the front cab mount. The bracket mounts with two (GR 8) 9/16" hex bolts, hex nuts and split washers.

• Each leaf spring pack and rear shackle secure with three (GR 8) 13/16” hex bolts, 7/8” hex torque nuts and flat washers.

• Each backing plate mounts to the axle’s flange using four (GR 8) 9/16" hex bolts, hex nuts and split washers

• The steering box mounts to the LH frame with four (GR 8) 5/8" hex bolts and split washers

• The idler support mounts to the RH frame rail with two (GR 8) 9/16" hex bolts and hex torque nuts

• The rear U-joint secures to the pinion’s saddle with two strap retainers and four (GR 8) 7/16" hex high crown flange bolts

• The lower power steering pump bracket mounts to the engine block’s LH lower face using two (GR 8) 5/8” hex bolts and split washer

• The compressor flange’s bottom outside corner mounts with one (GR 8) 1/2" hex bolt, hex nut, split washer and flat washer.

• The A/C muffler assembly’s front line secures to the compressor flange’s top rear RH corner with a strap retainer. The retainer is stamped “8”. The retainer mounts with a (GR 8) 1/2” hex bolt

• The upper steering shaft’s splines insert into the intermediate shaft’s pot joint. Mark the shafts so the splines line-up easing reinstallation. The pot joint assembly secures with a bolt clamp, a round flat top (GR 8) carriage bolt, and a *hex nut.

• Each sport mirror mounts to a door with a plastic gasket, a backing plate, and three stainless (GR 8) #2 phillips counter sunk head screws.

[53burb]

GREAT info!!! thx for sharing and writing this up!!

[HotWheelsFan]

Stamps on the bolts, other than the grade markings, would be the mfg. stamp ID. Symbols were also used. You should be able to search for info on the web. AMK Bolts might also have useful info...


Bob

[CKfan]

That required a lot of time and effort. Appreciated!

[leftybass209]

Great information! For those that don't know, a lot more goes into the grading of a bolt, and where it's used, rather than just needing the strongest bolt for a given situation.
Sometimes a bolt has a lower rating because it needs a sheer effect built in for safety purposes.
My dad was once in an accident driving a front loading garbage truck, and if he didn't jump out, the steering wheel would have went straight through his chest, because it punctured the seat and put a fat deep dent in the back of the cab.

Someone thought grade 8 was the right fastener to install that column and all of its hardware.

[kev2809]

good info! this should be a sticky for sure

[Accelo]

While I fully appreciate the data. However, I am a little confused.
It seems sometimes the wrench/head size is given and sometimes the bolt shank diameter.
Technically it's correct to reference bolts by the shank diameter.
Especially since they can, and do, have different head sizes.
Cheers.

[swclassics]

Great info! Thanks for taking the time.

[pjmoreland]

Originally Posted by 71CHEVYSHORTBED402

• The shift control bracket mounts to the LH frame rail’s inner wall using the two holes located immediately in front of the front cab mount. The bracket mounts with two (GR 8) 9/16" hex bolts, hex nuts and split washers.

Today I was under my truck working on something completely unrelated, and I noticed that the bolts securing my shift control bracket to the frame rail were grade 307A, which, according to the following link, appears to be the lowest grade made. They've been on there a long time based on their dark color. I had your post here floating around in the back of my mind, so I dug around in my collection of miscellaneous bolts, found a pair if grade 8 bolts, and threw them on there. I'm thinking this isn't a high-load application, but it can't hurt to have grade 8 hardware.

https://www.boltdepot.com/fastener-i...ade-chart.aspx

[kev2809]

it never hurts to have grade 8, i try to run them every time i replace a bolt. peace of mind at least

[71CHEVYSHORTBED402]

Originally Posted by Accelo

While I fully appreciate the data. However, I am a little confused.
It seems sometimes the wrench/head size is given and sometimes the bolt shank diameter.
Technically it's correct to reference bolts by the shank diameter.
Especially since they can, and do, have different head sizes.
Cheers.

I have the shank & thread data as well - The intent was to just point out where this truck had GR 8, and just happened to list them by hex size. Speak of questioning stuff, I wonder why my power steering pump bracket took two GR 8 bolts. Perhaps they were switched at some point, though they're original type bolts. I only question that because the brackets mounted to the block are primarily GR 5 bolts. The A/C has some GR 8, but none to the engine block.

I think the idea being it's a major *()^)^ to have to remove a busted GR 8 from a block.

[71CHEVYSHORTBED402]

Originally Posted by kev2809

it never hurts to have grade 8, i try to run them every time i replace a bolt. peace of mind at least

Point taken, but take a peak at the 5th post. That and I don't know, I think you have to be careful around a cast iron block.