Grade 8 Bolts
 

Should I put Grade 8s::::::
Clamshell Mounts to Frame
Mounts to Engine
Bellhousing
Etc.
Etc.

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.

Re: Grade 8 Bolts
 

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Yes... G8, where necessary!

Before I became fully aware of the various grades, I used whatever was available...

-klb

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.

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/

Re: Grade 8 Bolts
 

I recently bought new motor mounts and they came with grade 5 bolts. I also bought grade 5 bolts to replace the rest of the engine mounting bolts as well. Grade 5 will be fine for a daily driver, unless you have some serious power you're putting down :lol:

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.

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.

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.