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PostPosted: Tue Dec 14, 2021 1:03 pm 
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The torque arm that is supposed to be on the top of the rear valve cover on a 308 and is clearly not on mine.  The 4? V12 conversions the were build in the 80's all followed the path of the 1st, which moved the torque arm to the rear of the differential because that is at least as far from the crank centerline and looks better.....but its also wrong  the only real mistake I saw in the book/manual converter #1 (David Goldsmith) put together so I won't be doing that.

Why the stock location is right and the goldsmith location wrong takes a little explanation. The 308 V8 is a flatplane crank so it vibrates twice as bad as a 4 cylinder with no balance shafts.  The solution to that is  4 fancy motor mounts at the lower 4 corner of the eng/trans assembly that are rubber but also have a spring and let the motor/trans bounce up/down a LOT  but not front/back or side/side without that vibration transferring to the chassis.  But that cause the assembly to also want to rotate about the axles and because the mounts are basically in a horizontal line with the axles, the reaction to torque at the axles is a rotation that an up/down at the mount, which they are not designed to stop.  The OEM ferrari torque arm is basically horizontal to the ground and perpendicular to the mounts free up/down motion leaving the engine free to bounce up/down due to engine vibration but not with torque. 

The Goldsmith design has 2 mistakes.  First it assumes the reactions are at the crank, but the crank forces are constrained fully by the transaxle so the net reactions are at the axle making his arm design way too short.  The second is that its inline with the motor mount so torque reaction cause the engine to move up/down at the mounts and the mounts are designed to not stop that.  Together I think that torque arm just make the problem worse than no arm at all and he does talk about shifting issues and solving it be replacing the front (iirc) motor mounts with daytona mounts which are I guess the same size but solid rubber...which is also an issue because the the 2 rear mounts will still reaction up/down to torque.

Stupid simple part...stupid complicated explanation but it's been on the to-do list a long time and with the engine running (and even running badly still making enough torque to spin the 285 tires) and the cam cover coming off it seems like time to get it done.


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PostPosted: Tue Dec 14, 2021 1:11 pm 
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mk e wrote:
replacing the front (iirc) motor mounts with daytona mounts which are I guess the same size but solid rubber...


Why can't you just do this? Since your V12 is smoooooooooth as glass, you don't need floppy engine mounts designed for a buzzy flat crank V8.
Each bank has an up-down shake, but two banks 90 degrees out of phase together produce a rotating couple.... FYI.

mk e wrote:
Stupid simple part...stupid complicated explanation but it's been on the to-do list a long time and with the engine running (and even running badly still making enough torque to spin the 285 tires) and the cam cover coming off it seems like time to get it done.


Don't do that... Your cover is so much nicer without the dogbone mount, and I don't think you need it.
4 engine mounts is enough, as long as they can take the loads indicated by axle torque divided by the fore/aft distance between the mounts.


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PostPosted: Tue Dec 14, 2021 1:42 pm 
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TheDarkSideOfWill wrote:
mk e wrote:
replacing the front (iirc) motor mounts with daytona mounts which are I guess the same size but solid rubber...


Why can't you just do this? Since your V12 is smoooooooooth as glass, you don't need floppy engine mounts designed for a buzzy flat crank V8..


Just is as goldsmith did with 2 is wrong but all 4 would would work and is something I'm considering. He complained about vibration with 4 but.....yeah. I remember somebody found a urethans mount....mustang I think that was nearly a bolt-in but I'm remembering they failed with heat......Sean it was, I'll reach out.

If I do add an arm is will be not be 2V style ......whatever I do will be neat.


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PostPosted: Tue Dec 14, 2021 2:13 pm 
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mk e wrote:
TheDarkSideOfWill wrote:
Why can't you just do this? Since your V12 is smoooooooooth as glass, you don't need floppy engine mounts designed for a buzzy flat crank V8..


Just is as goldsmith did with 2 is wrong but all 4 would would work and is something I'm considering. He complained about vibration with 4 but.....yeah. I remember somebody found a urethans mount....mustang I think that was nearly a bolt-in but I'm remembering they failed with heat......Sean it was, I'll reach out.

If I do add an arm is will be not be 2V style ......whatever I do will be neat.


Where's your machined level pad for balancing a silver dollar on while the engine is idling?

V12's are smoooooth... Don't worry about how stiff the mounts are. I have 4 point urethane mounts on my cross-plane V8 and plenty smooth for me... certainly smoother than the stock 2.8 V6 on urethane mounts.


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PostPosted: Tue Dec 14, 2021 2:51 pm 
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I fabricated a urethane mount using black skate board wheels. A wide variety of durometers are available.


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PostPosted: Tue Dec 14, 2021 3:08 pm 
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kens wrote:
I fabricated a urethane mount using black skate board wheels. A wide variety of durometers are available.


Interesting, pics?

here are modified mustang mounts a few have fitted


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PostPosted: Tue Dec 14, 2021 11:11 pm 
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Sean says the mustang mounts failed pretty quickly and are not worth bothering with so I'd need a different solution.


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PostPosted: Tue Dec 14, 2021 11:39 pm 
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mk e wrote:
Interesting, pics?



Repair of the broken bracket has been pending, thanks for the reminder.


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PostPosted: Wed Dec 15, 2021 8:58 am 
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I was ALMOST able to put the rear cam cover.  When the intakes are off this time I'll add a bevel to the outside edge so the cam covers will clear incase there is a next time.  I thought it kind of cool the the cover bolt bosses dropped right into clearance around the TBs like it was planned.....sometimes I amaze myself 

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I'm now told the urethane mustang mounts fail in sort order and are not worth bothering with.  Looking quickly this morning I could lower the stock torque arm  and mount it to the rear edge of the cam cover....that wouldn't look bad. 
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There is of course no car structure to bolt it to in that location, just a sheetmetal panel so that would be additional work to add but not a lot of work I guess.  Still thinking


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PostPosted: Wed Dec 15, 2021 10:25 am 
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It's almost like you spent years building it specifically to achieve sub-millimeter clearances everywhere. Clearance is clearance like the machinists say.

You just need to get 4 Daytona mounts and call it solved. Do they bolt in place of the 308 mounts?

Edit: Nearing the end of my project, I jump at every chance available to buy something that bolts in so that I don't have to make yet another thing every time I turn around... and I haven't done a fraction of the fabrication you have.


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