What did you do today to your 3/S?

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Originally Posted by DK77

IIRC, $800 but Nelson was doing a GB to get the price down to $550 each... Don't know what happened with that though.

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We're in the GB and it's $650 presently, It's a steal...so much weight loss, so much more room to route shit around your engine....and so much easier for 75 conversion where half the bosses for the front and rear mounts are not there.

today I send out my aem ems V2 to AEM to diagnose my problems. 1.5 years of coolant temp issues is a bit long.

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Originally Posted by n2nsanity

Interesting... I'm all about making things simple. As others have mentioned, I'd be concerned about not having the trans mount. No reason you couldn't still use it right?
How much is this thing? Maybe I could sell all my extra mounts and get one of these :)

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Sure, it's only 1/4", you might have to bore out the holes a bit but you'd be fine. It's $650 if you get in on the group buy, Nelson has said $600 if we get 15. Do eet!

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Originally Posted by MR2

We're in the GB and it's $650 presently, It's a steal...so much weight loss, so much more room to route shit around your engine....and so much easier for 75 conversion where half the bosses for the front and rear mounts are not there.

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You say 75 conversion? Thought you were just gonna go with a 74block/75crank. That was on my list.
But, now you're talking about a complete 75 longblock? Now I'm really interested...
I still have hopes for a 4.0tt one day. That along with a little weight savings would be amazing :)

I really haven't seen much done with our cars as far as engines. With time, money and some creativity I'm sure we could accomplish a lot. Too bad I'm lacking 2 of those, lol.

If this group buy stays open long enough, it's a possibility, but I'd really prefer that $600 to go towards my tt conversion. But man, for a simple chunk of metal, this thing is awesome!

@Intropy, that's what I was thinking. You could just bore out the holes on the bracket a little.

was looking 74/75....but the 75 will let you go a 4.2L :) so why the hell not! see the holy grail thread :)

searched, not seeing it
link please :)

3KGT Holy Grail - 3000GT/Stealth International Message Center

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Originally Posted by MR2

you can't still use it as the stock mount holes will no-longer line up.

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Pretty much what I figured. You could probably slot the original mounting holes to make it go back in...

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Originally Posted by MR2

there is no need for a trans mount due to a few things...iirc the plate takes the TC strain

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Huh? This plate doesn't go near the TC:

http://i165.photobucket.com/albums/u...n/3cafe265.jpg

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Originally Posted by MR2

and now that the engine is unable to wobble (again, with the plate) there is no need to stabilise the gearbox end of things

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People have used solid mounts for years. Why don't any of them ditch the trans mount? You really think this aluminum plate is more rigid than the stock stuff with solids?

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Originally Posted by MR2

keep in mind the weight center is pretty much 1/4 into the engine, so as long as whatever is holding everything has a very strong grip of the engine I can't see it being an issue.

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The CG being in the block doesn't render the trans mount useless. It could certainly reduce the amplitude of the cyclic stress on these aluminum welds... Again, if this thing isn't heat treated post-welding, the heat affected zone around those welds will be considerably weakened. This plate surviving one or two passes down the track doesn't mean anything because regardless of the stress level, aluminum fatigues.

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Originally Posted by MR2

Don't stress, if it was a horrid idea some of the big names would have said something by now.

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This is some of the most ridiculous logic I've ever heard. First of all, I hope you don't apply this logic to the rest of your life. Second, the big names avoid Nelson's shit-fest threads like the plague. Third, this is the most I've seen this plate discussed.

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Originally Posted by AdamVR4

People have used solid mounts for years. Why don't any of them ditch the trans mount? You really think this aluminum plate is more rigid than the stock stuff with solids?

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It's because our mounting system is essentially 3 point torque-roll-axis mounting system (the front and rear mounts, for calculation purposes, are considered one piece). Taking off the trans mount turns it into a 2 point TRA system - this is statically indeterminate and increases the mount stresses sky high.

see the quick primer on engine mounts here:
http://www.vecom.org/events/04Erdely...layouttool.pdf

Given where the weight is centered with the engine/tranny combo, what will likely happen is that the driver side mount will no longer support the weight of the engine upward. In fact, just from basic statics, it might actually pull downward on the engine assembly. that means the weight AND torque pulses will be taken by that plate. You better hope it's thick as shit.

on a side note, this is why it's acceptable to run with a bad rear engine mount for so long (or run without a front engine mount for some big turbo guys). As long as there is a healthy one in the front or back, all you're really doing is reducing the stiffness of the roll stop by half. It doesn't critically support the weight of the engine.

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Originally Posted by i3igpete

It's because our mounting system is essentially 3 point torque-roll-axis mounting system (the front and rear mounts, for calculation purposes, are considered one piece). Taking off the trans mount turns it into a 2 point TRA system - this is statically indeterminate and increases the mount stresses sky high.

see the quick primer on engine mounts here:
http://www.vecom.org/events/04Erdely...layouttool.pdf

Given where the weight is centered with the engine/tranny combo, what will likely happen is that the driver side mount will no longer support the weight of the engine upward. In fact, just from basic statics, it might actually pull downward on the engine assembly. that means the weight AND torque pulses will be taken by that plate. You better hope it's thick as shit.

on a side note, this is why it's acceptable to run with a bad rear engine mount for so long (or run without a front engine mount for some big turbo guys). As long as there is a healthy one in the front or back, all you're really doing is reducing the stiffness of the roll stop by half. It doesn't critically support the weight of the engine.

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Interesting...

Quick and dirty, please look for mistakes...


Let's pretend you're making 750 ft-lbs of torque and the center line of the crank is 18" from each mount. It's conservative to assume the torque load is fully applied to just one of the mounts, and the plate begins life as 6061-T6.

750 ft-lbs / 1.5 ft = 500 lbs on the mount. Multiply by 12+ to account for torque multiplication in 1st gear... 6000 lbs. ADD the weight of the engine to the mount that's loaded in compression. ~6500 lbs.

Whether the plate is heat treated post-weld or not, if the welds are beefy, the weakest point will be in the sheet aluminum. The Heat affected zone could have an ultimate tensile strength of 18 ksi (8 ksi yield). If the part is heat treated after welding, this jumps to 45 ksi (and 40 ksi)... Not trivial.

If I had to guess, the effective weld length looks like ~5 inches. If you assume the aluminum is .375" thick, you're talking about an effective cross sectional area in the HAZ of ~ 1.875 in^2

18,000 psi * 1.88 in^2 = 33,750 lbs required to cause fracture (safety factor = 5.2)
8,000 psi * 1.88 in^2 = 15,000 lbs required to cause yield (safety factor = 2.5)

So there are the static safety factors. Fatigue makes the problem much more interesting...