Grade 5 bolts or Grade 8 bolts

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grocerygetter247
Posts: 2
Joined: December 3rd, 2022, 10:45 pm

Grade 5 bolts or Grade 8 bolts

Post by grocerygetter247 »

New here and first post so far been learning a lot so thanks y'all for the info and knowledge on the engine. This is a question I have that seems to have mixed answers everywhere. I've used grade 8 bolts when mounting engines on an engine stand in the past and it worked great however when talking with different people about engine rebuilds recently I realized some people are big believers in using grade 5 bolts and not grade 8 bolts. I was told in the past to always use grade 8 bolts when mounting engines to engine stands but I figured I'll ask this question here since I'm sure a lot of people on here have mounted the 4.0 engine on an engine stand. Also if y'all can add your reason to why you prefer that grade of bolt over the other would help as well. Thanks!
Randy Bobandi
I made it to triple digits!
I made it to triple digits!
Posts: 152
Joined: December 22nd, 2020, 8:50 am

Re: Grade 5 bolts or Grade 8 bolts

Post by Randy Bobandi »

grocerygetter247 wrote: January 17th, 2023, 3:43 pm I realized some people are big believers in using grade 5 bolts and not grade 8 bolts
How did you come to this realization?

4 bolts fasten almost all gas engines to engine stands. Is it the $.25 per bolt cost savings that folks are citing to recommend grade 5? $1.00?

That's the only advantage to grade 5, right?

Or is it the fact that the shear stress from a 200#-600# engine isn't even close to limits of 4 Grade 5 bolts. Two 3/8" bolts and two 7/16" bolts in grade 5 can handle about 250,000 PSI in shear stress. Grade 8 in the same size bolts would be close to 400,000 PSI. You're more than safe either way. Maybe some folks prefer silver to gold?
grocerygetter247
Posts: 2
Joined: December 3rd, 2022, 10:45 pm

Re: Grade 5 bolts or Grade 8 bolts

Post by grocerygetter247 »

That's why I asked this question lol I always used grade 8 bolts but talking with others there are quite a few people who prefer grade 5 over grade 8 when putting an engine on a stand so I wanted to ask this question here just out of curiosity as to what people on here use
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