<VV> Re: LM mounts

[Kirby Smith]

To follow up on my previous comments...

Clarks sent me a replacement mount and generously included a new 
figure-8 washer, which easily fit the mount.  The old washer was very 
tight on the new mount also, but freer than on the mount I sent back, 
and would have required significant reaming to work.  It is possible 
that deformation from the nuts was a factor.  I did have to do a bit of 
filing on the sides of the slots in the cradle to get the mount to pass 
through it.  Hence, I still suspect the center-to-center spacing.

Anyway, in preparation for mounting, I slightly slotted the wide side 
mounting holes just in case, and milled a much larger slot in the top to 
clear the rear panel support.  It is true that once loaded by the engine 
weight, there is enough drop to mostly clear the support, but where the 
support curves toward the rear it would be very close to the original 
slot corner, and installation unweighted would be more difficult, I expect.

Measuring from the top of the mount to the rear frame, the unloaded 
dimension was 1.415.  Loaded, but undriven, it is 1.115.  The 
measurement is taken on the driver's side, about 3/8 inch from the rear. 
  I do not think the mount upper surface is closely parallel to the top 
of the frame, so there may be differences depending on where it is 
measured.  The thickness of the mount top I measured to be 0.212, which 
may be subtracted from the above numbers to compare with the under 
surface to frame dimension of an inch Padgett previously reported.

This mount raised the rear of my engine at least an inch.  The seal gap 
at the rear is now slighly narrower than at the front.  I guess the rear 
mount had seen better times.  I just can't recall how peaked it looked 
when new.  My OEM mount is fairly flat across the top when loaded (or 
unloaded, for that matter).

Padgett: In your instructions you call for 60 lb-ft of torque on the 
lock nuts attaching the mount to the engine cradle, consistent with my 
1965 shop manual.  However, my 1966 supplement calls for 30 lb-ft in the 
exact same table.  Is this a known discrepancy with a consensus as to 
which is correct?  While I believe the nuts and bolts can take the 
higher torque, I see no reason why they should need it.  The nuts are 
locknuts, and ahouldn't need torque for retention.  Most forces put on 
the interface are taken by the rubber mount, so I would expect shear and 
other effects that might work the interface to be mild.  Opinions are 
welcome, since I'm only guessing here.

kirby



Kirby Smith wrote:
> Now that I have taken the initial steps (thanks Padgett) for 
> installation, in my opinion this heavy duty mount is a good idea badly 
> executed.  Beyond the barely long enough, untapered bolts used for studs 
> (GM made them long and pointy for a reason), and beyond the reported 
> need to drag holes and slots as required (the LM OEM unit has slots for 
> the mounting bolts for a reason), and beyond my uncertainty w.r.t. the 
> effect on strength of welding on the heads of the Grade 8 bolts used to 
> build it, the example I got from Clarks doesn't fit the figure-8 washer, 
> which does fit the two LM and one EM motor mounts in my possession.  It 
> is no more likely to fit the engine cradle, which appears to have even 
> less freeplay.
> 
> It would seem that a jig was not used (as it should have been) to 
> establish the alignment of the bolts used for studs.
> 
> I'm not going to mill the washer and the engine cradle to accommodate 
> this out-of-tolerance mount.  I'm going to ask Clarks to replace it with 
> one that fits the figure-8 washer.  Then I can determine what milling is 
> needed to get it to fit the frame.
> 
> kirby
> 66 turbo Corsa (bought new)
> 
> 
> Padgett wrote:
> 
>>
>>> Jeff Brekke no longer have any of the mounts he was making, which I 
>>> had heard were quite good?
>>
>>
>>
>> Had virtue of having replaceable inserts but I e-mailed Jeff and he 
>> did not have any. When he did they were a little more expensive.
>>
>> Mount had no indication of origin or any markings on it. Was part of a 
>> paper tag attached but not enough to read. I had to e-mail Lon to ask 
>> about them and are on page 28 of Clark's supplemental catalog.
>>
>>  > couldn't use the "figure 8" washer under the two stud nuts, the studs
>>  > weren't long enough
>>
>> I remembered these feeling a bit a bit short but remember the factory 
>> setting for the rear mount nuts (65 FSM specifications (in back) page 
>> 5) is 50-60 ft-lb.
>>
>> The jpg at http://padgett.ws/files/newmntstds.jpg was taken after 
>> torqueing both to 50 lb-ft and then removing.  5.5 to 6 threads were 
>> engaged (turns before nut fell off) on both. Nuts were replaced and 
>> retorqued then one was removed again for the photo. Remember these are 
>> locking nuts so taller than most. Note that the threads come to within 
>> about a 1/16 of the end unlike the factory studs which have a tapered 
>> guide end. I believe this is sufficient though barely and another 1/8" 
>> would be nice. If someone with more expert/current knowledge has a 
>> different opinion please let me know.
>>
>> I know this is getting a bit AR but only took about ten minutes and it 
>> is 68 degrees in the garage.
>>
>> Padgett
>>