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Gromit · 03-14-2016, 05:25 PM

Since today is Pi day (3.14) I think I can ask about your impressions of the lift plate..

Since you got the motor in and out okay yours was a good test to prove it did hold the entire weight of the motor and trans; but I think it may have been close..

I got curious about this after seeing your photos - Here is the calculation for the pull-out strength of those four 5/16-24 manifold bolts as best as I can tell:

pi x Pitch Diameter x % thread x length of engagement x shear strength of material.

So for example:

3.1415926 x .3125 x (((.3125-.2716)/.01299))/100) x .5 x 28,000psi = 440 lbs per bolt x 4 = 1,760 lbs x 50% safety factor = 880 lbs.

I'm guesstimating the weight of your motor and trans at 750 to 800? So if you go over any bumps with that motor hanging from the lift it seems to me it might go over the 880. But maybe that is in the safety factor..

By pull-out meaning by shearing the female threads in the aluminum manifold at the thread roots.

28,000 psi being the yield strength of cast aluminum AA but there are so many alloys it is hard to say.

The .2716 is the size of the letter "I" drill used before tapping the 5/16 bolt holes in the manifold.

But I don't want to hijack the thread so just mean this as food for thought for next time you pull that motor!

03-14-2016, 05:25 PM	#9
Gromit Registered User Join Date: Jul 2015 Location: Central Coast, CA Posts: 501	Re: Engine bay for a facelift. Since today is Pi day (3.14) I think I can ask about your impressions of the lift plate.. Since you got the motor in and out okay yours was a good test to prove it did hold the entire weight of the motor and trans; but I think it may have been close.. I got curious about this after seeing your photos - Here is the calculation for the pull-out strength of those four 5/16-24 manifold bolts as best as I can tell: pi x Pitch Diameter x % thread x length of engagement x shear strength of material. So for example: 3.1415926 x .3125 x (((.3125-.2716)/.01299))/100) x .5 x 28,000psi = 440 lbs per bolt x 4 = 1,760 lbs x 50% safety factor = 880 lbs. I'm guesstimating the weight of your motor and trans at 750 to 800? So if you go over any bumps with that motor hanging from the lift it seems to me it might go over the 880. But maybe that is in the safety factor.. By pull-out meaning by shearing the female threads in the aluminum manifold at the thread roots. 28,000 psi being the yield strength of cast aluminum AA but there are so many alloys it is hard to say. The .2716 is the size of the letter "I" drill used before tapping the 5/16 bolt holes in the manifold. But I don't want to hijack the thread so just mean this as food for thought for next time you pull that motor!