I'm trying to mount an engine to an engine stand and am having trouble trying to find bolts to do it with. I have heard grade 5 bolts are strong enough, but then a local parts store said grade 8 would be recommended since it's an expensive gamble. So what grade does everyone use?? I believe I need 12 mm x 1.75 x approx. 100mm to secrue it in my mind and am having trouble finding anything in grade 8 over 80 mm long.
I bought an engine stand just last week. I went to the Ace Hardware right next door to the AutoZone I got my stand from, and bought the bolts to mount an '88 V6 to it. 12mm x 1.75 mm; two were roughly 100mm long and two were about 80 mm long--they cost about a buck each. (I say "about" because I just said, "Hmm, that looks long enough, and so do these..." and took a chance which, it turned out, worked fine.) I'm just using whatever they happened to have on hand, to tell the truth; I didn't even think about bolt grade or anything. But I figure they're probably at least grade 5.
Is this for the Cadillac motor?
Buy at least one 12 x 1.75 nut and a handful of washers. On the Fiero motor, one of the mounting points I used has no threads, but one of the long bolts works fine with a nut and washer on the other end. (This mounting point is on the RH side as you look at the flywheel. Cadillac 4.9 ought to be similar IIRC.)
I hope that helps. Hope your swap goes well!
Ed
PS See you at FieroRama.
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05:13 PM
Vonov Member
Posts: 3745 From: Nashville,TN,USA Registered: May 2004
Strongly recommend Grade 8...if a lesser bolt decides to let go, like when you're turning the engine upside down to work on the main bearing caps, the others will have to carry the extra load, and will usually fail swiftly thereafter. Even if nothing, including you, is damaged (very unlikely), there's still the aggravation of (a) picking the engine back up, and (b) getting the broken bolts out of your block. Most engine/transmission mounting bolts found in the bellhousing will serve your purpose.
------------------ 88 Formula, "Asphalt Aviator"
Celebrate Artesian New Year!!!
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05:20 PM
1MohrFiero Member
Posts: 4363 From: Paducah, Ky Registered: Apr 2003
I thought Grade 8 was the minimum that metric bolts were made.
Metric bolts come in an assortment of grades just like SAE bolts, because for a designer it's cheapest to use a bolt that is strong enough for the job and if a grade 6.8 or 8.8 bolt is strong enough it saves money.
Even a grade 5 equivalent bolt will withstand 120,000 psi of stress, so theoretically a bolt of 1 square inch of cross sectional area would support 60 tons before breaking. Of course, a safety margin of 3x is recommended for low tech work so 40ksi is a good working number. A 12mm bolt has about a 10mm diameter cross sectional area, so a 40ksi load limit works out to be 4,870 pounds that you would want to subject that bolt to. Looking at the motor's CG and fully dressed weight, it appears that the top bolts would be subject to loads way less than 1,000 each. That means that grade 5 equivalent bolts would be far, far in excess of what loads they would be subject to.
Originally posted by JazzMan: Metric bolts come in an assortment of grades just like SAE bolts, because for a designer it's cheapest to use a bolt that is strong enough for the job and if a grade 6.8 or 8.8 bolt is strong enough it saves money.
Even a grade 5 equivalent bolt will withstand 120,000 psi of stress, so theoretically a bolt of 1 square inch of cross sectional area would support 60 tons before breaking. Of course, a safety margin of 3x is recommended for low tech work so 40ksi is a good working number. A 12mm bolt has about a 10mm diameter cross sectional area, so a 40ksi load limit works out to be 4,870 pounds that you would want to subject that bolt to. Looking at the motor's CG and fully dressed weight, it appears that the top bolts would be subject to loads way less than 1,000 each. That means that grade 5 equivalent bolts would be far, far in excess of what loads they would be subject to.
JazzMan
You know, after reading other posts in this thread I was starting to worry about the bolts I used, but after reading that, I'm not worried anymore. If I haven't given you a + already you'll get one from me shortly.
Ed
EDIT: The real irony is that I checked them later and found they were grade 8.8.
[This message has been edited by edhering (edited 08-25-2004).]
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08:23 PM
DanFiero Member
Posts: 2815 From: Cedar Rapids, Iowa Registered: Jul 2002
Thanks for all the replys + for you all. I looked all over town and nobody had a grade 8 metric bolt long enough to do the job. I found only one place that had grade 5 bolts long enough, so that is what I went with. I even went to a parts store and engine place and no one seemed to know they're head from another part of their boday as to what is standard practice for this. And after a little work the engine seems to be safely mounted and holding fine with the grade 5 bolts.
Thanks for all the replys + for you all. I looked all over town and nobody had a grade 8 metric bolt long enough to do the job. I found only one place that had grade 5 bolts long enough, so that is what I went with. I even went to a parts store and engine place and no one seemed to know they're head from another part of their boday as to what is standard practice for this. And after a little work the engine seems to be safely mounted and holding fine with the grade 5 bolts.
Dan
Though technically metric bolts are graded with a #.# scheme instead of a grade # scheme.
Thanks for all the replys + for you all. I looked all over town and nobody had a grade 8 metric bolt long enough to do the job. I found only one place that had grade 5 bolts long enough, so that is what I went with. I even went to a parts store and engine place and no one seemed to know they're head from another part of their boday as to what is standard practice for this. And after a little work the engine seems to be safely mounted and holding fine with the grade 5 bolts.
