can Gd 8 bolt replace crossmember rivet? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cib101abn · 11-22-2004, 10:17 AM

I have a 79 Chevy P/U that previous owner had collision in, the front cross member is slightly twisted and popped a rivet on the cab side letting it lift up about 1 inch in the twist...thought about bending it back down and replacing rivet with a grade 8 bolt, will this work or does it have to be welded? thanks, bob

Prerunner1982 · 11-22-2004, 11:07 AM

i know quiet a few people who use grade 8 bolts on suspension mounts. Dont see why you couldnt use them on the crossmember as well. just double check the torque on it occasionally and might be beneficial to use a thread lock compound.

BigChevMan · 11-22-2004, 09:55 PM

use grade 5 bolts..that would be equal to the rivet. Grade 8 bolts would be too brittle for that application. A grade 8 bolt would just shear off whereas a grade 5 bolt would bend before it popped...like the factory rivet.

crazy longhorn · 11-23-2004, 01:29 AM

I dont know where the thread is , but there was an article showing fatigue strenghts in both compression & tension......the grade 8 , while a bit overkill for the app, is stronger than a grade 5. The article went on to say that the rockwell hardness of the grade 8 was not high enough to make it brittle. when a grade 8 fails, it fails catostrophiclly......but it is still far beyond the point where the same sized grade 5 bolt would fail (that is in tension, or compression) ! I have used many grade 8 fasteners on the chassis & suspension on my longhorn, & not had a bit of problem

A grade 5 would be plenty strong for that app.....but IMO, an 8 would be better(even tho a bit overkill)..... crazyL

Tx Firefighter · 11-23-2004, 07:48 AM

There have been several colorful discussions here about the grade 5 versus grade 8 bolts. Like Longhorn said, the grade 5 will be long gone before the grade 8 will break. Besides, there are plenty of grade 8 bolts in suspensions, stock from the factory. That tells me something.

Also, back in the day when I was in A&P (airplane mechanic) school, they taught us that the FAA requires using at least a grade 8 bolt, when replacing a rivet with a bolt. The FAA is the authority on every craft that leaves the ground in the US.

64fleetside · 11-23-2004, 09:59 AM

Back in the day when I worked at the dealership, the factory recommended replacing bad or removed rivits with grade 8 hardware. If its good enough for the manufacturer, it's good enough for me! Brian

1-PU70 · 11-23-2004, 10:30 AM

Not to make things more confusing there is the issue of fine thread and corse thread. Fine thread is stronger then corse thread.

68LSS1 · 11-25-2004, 04:00 AM

Ya, someone make those last two threads a sticky please?

Or we'll just have to make it a semi annual arguement.

68LSS1 · 11-25-2004, 06:07 AM

Here's the last thread and here's a link to the grade 5/8 write up.

Truckhead · 11-29-2004, 01:25 PM

How about using Titainium bolts?

Tx Firefighter · 11-29-2004, 02:55 PM

Quote:

Originally Posted by Truckhead

How about using Titainium bolts?

Why? Regular grade 8 steel bolts are more than enough.

11-22-2004, 10:17 AM	#1
cib101abn Screaming Eagle Join Date: Oct 2004 Location: SW of Houston Posts: 288	can Gd 8 bolt replace crossmember rivet? I have a 79 Chevy P/U that previous owner had collision in, the front cross member is slightly twisted and popped a rivet on the cab side letting it lift up about 1 inch in the twist...thought about bending it back down and replacing rivet with a grade 8 bolt, will this work or does it have to be welded? thanks, bob __________________ "Basic Research is what I am doing when I don't know what I am doing." Dr. Werner VonBraun (Rocket Scientist) Contributing Member 79 GMC SWB w/402 79 Chev SWB w400 sm blk being built remnants of 72 Cheyenne (selling)

11-23-2004, 01:29 AM	#4
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	I dont know where the thread is , but there was an article showing fatigue strenghts in both compression & tension......the grade 8 , while a bit overkill for the app, is stronger than a grade 5. The article went on to say that the rockwell hardness of the grade 8 was not high enough to make it brittle. when a grade 8 fails, it fails catostrophiclly......but it is still far beyond the point where the same sized grade 5 bolt would fail (that is in tension, or compression) ! I have used many grade 8 fasteners on the chassis & suspension on my longhorn, & not had a bit of problem A grade 5 would be plenty strong for that app.....but IMO, an 8 would be better(even tho a bit overkill)..... crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

11-23-2004, 07:48 AM	#5
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	There have been several colorful discussions here about the grade 5 versus grade 8 bolts. Like Longhorn said, the grade 5 will be long gone before the grade 8 will break. Besides, there are plenty of grade 8 bolts in suspensions, stock from the factory. That tells me something. Also, back in the day when I was in A&P (airplane mechanic) school, they taught us that the FAA requires using at least a grade 8 bolt, when replacing a rivet with a bolt. The FAA is the authority on every craft that leaves the ground in the US. __________________ I'm on the Instagram- @Gearhead_Kevin

11-23-2004, 10:30 AM	#7
1-PU70 Registered User Join Date: Apr 2000 Location: Bradenton, FL Posts: 1,036	Not to make things more confusing there is the issue of fine thread and corse thread. Fine thread is stronger then corse thread. __________________ 1970 CST/10 402,700R4,3:73 posi,AC,PS,PB,TLT,PW,Buckets with heaters

11-25-2004, 04:00 AM	#8
68LSS1 Registered User Join Date: Dec 2002 Location: Tampa Posts: 1,191	Ya, someone make those last two threads a sticky please? Or we'll just have to make it a semi annual arguement. __________________ '68 Short Step LS1/T56, Hydratech, Fatman Fabrications Stage III, Baer, Hot Rods to Hell, US Body, S&W, etc

11-22-2004, 11:07 AM	#2
Prerunner1982 Registered User Join Date: Oct 2002 Location: Edmond, OK Posts: 5,904	i know quiet a few people who use grade 8 bolts on suspension mounts. Dont see why you couldnt use them on the crossmember as well. just double check the torque on it occasionally and might be beneficial to use a thread lock compound.

11-22-2004, 09:55 PM	#3
BigChevMan My Thoughts Exactly! Join Date: Jan 2003 Location: Ohio Posts: 140	use grade 5 bolts..that would be equal to the rivet. Grade 8 bolts would be too brittle for that application. A grade 8 bolt would just shear off whereas a grade 5 bolt would bend before it popped...like the factory rivet.

11-23-2004, 09:59 AM	#6
64fleetside Registered User Join Date: Apr 2004 Location: arkieland Posts: 1,070	Back in the day when I worked at the dealership, the factory recommended replacing bad or removed rivits with grade 8 hardware. If its good enough for the manufacturer, it's good enough for me! Brian

11-25-2004, 06:07 AM	#9
68LSS1 Registered User Join Date: Dec 2002 Location: Tampa Posts: 1,191	Here's the last thread and here's a link to the grade 5/8 write up. __________________ '68 Short Step LS1/T56, Hydratech, Fatman Fabrications Stage III, Baer, Hot Rods to Hell, US Body, S&W, etc

11-29-2004, 01:25 PM	#10
Truckhead 18436572 Join Date: Aug 2003 Location: Waynesboro, Va. Posts: 488	How about using Titainium bolts?

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.