Built some solid motor mounts.

[AndyMac]

Well, I started hanging the turbo on the pass side and decided the tolerances were so close that I should mount the motor solid.

I've heard rumblings of solid mounts causing the block to distort, but haven't seen any documented issues. So if you're anal, use polyurethane mounts instead.

I used a piece of 2" high x 4" wide x 6" long box steel that is 1/8" thick. Cut in half, it gave me two 2x4x3 blocks. The stock mounts are 1-5/8" high, so I took my plasma and cut 3/8 out of each side to give me the right height. If I didn't have the metal already, I would have tried for the right size box steal to start.

I also lucked out and found 4 high grade bolts with the the right thread pitch/size to fit the motor mount nuts. I installed the bolts from the inside out to act as studs similar to factory. I welded the heads of the bolts on the inside to hold them from turning. I found the studs to be offset about 1/2 to 3/4 of an inch. There are also positioning nubs beside the studs. I just drilled a hole and rounded the head of a bolt off and dropped in the hole. A tack of weld on the inside keeps it from going anywhere.

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To remove the mounts, get a 3/4" socket and undo the bottom mount nuts on either side. Jack up the motor with a piece of 2/4 running the length of the oil pan and a jack. You don't need to go too far, maybe 1" between the frame and mounts. Next, I used a 3/4" ratchet wrench to remove the nut from the top of the motor mount. The mounts still won't come out, so remove the two bolts/nuts(9/16") that hold the aluminum u-shaped mount holder above the motor mount. With a little friggin around, they come right out and the new ones go right in.
__________________
Andrew MacPherson
My turbo projects
1995 RT/10
1990 300zx ttv8
2002 WRX

 

[99 R/T 10]

Make sure the hood is up before attempting this............................. Just saying.

Nice write up though

 

[JonB]

I wonder how they'll SOUND ? Their actual name is "Isolators".....wont be any now!

 

[AndyMac]

I wonder how they'll SOUND ? Their actual name is "Isolators".....wont be any now!

You ever been in a Gen1? lol Seriously though, I thought long and hard about it, if it becomes an issue, I can still get revert back or go with polyurethane mounts.

I've used solid mounts in lots of my previous project cars and didn't really mind/notice the added noise/vibration.

Time will tell,

 

[2000_Black_RT10]

I definitely would not recommend using solid mounts, the chassis does flex torsionally (and the Viper suspension is quite stiff) and it also racks, the engine block is very stiff, something will fatigue over time with use.. just give it some time.. something is going to crack.. just cross your fingers it won't be the block... based on the open box design of your mount, my design engineering judgement will be that your mount will crack due to frame flex (torsionally) along the welds, and the U bracket will crack due to frame flex laterally (racking) at the engine block ears..

Edit.. sorry if the reply was a bit rash.. good job on doing this yourself though, good effort.

To explain further if needed.. (just ignore this babbling if you already know).. frame twist torsionally is easy enough to understand (twisting relative front to rear, i.e. front left up, right rear down) , but if curious about racking, this is when the left and right side of the frame rails can shift fore and aft independently. Analogy could be a ladder, 2 long posts that are connected with perpendicular steps, in order to stop a ladder from racking (i.e. one post can go up and the other can go down), they can have gussets. The frame crossmembers may not always keep the frame square in dynamic loading conditions (i.e. in a hard braking scenerio if left tire has more traction on pavement and the right has less traction on loose gravel which then the vehicle mass intertia and the opposing force due to traction tries to distort the frame forcing the left rail reaward relative to the right, meanwhile the car starts to spin around..). As there was a past Gen2 recall to add horizontal gussets on the frame (which was later optimized) with heavy rivets (otherwise.. smaller screws or rivets would shear) to reduce racking and encountered fatigue failure of welds and cracking of the cross members. Some can think that it's just a rock guard, but the plate under the transmission can be considered a large gusset tying the left and right frame together on a horizontal plane, which is a shear plate and reinforces the frame to prevent racking, hence the 10.9 grade bolts and thickness of the plate. If you ever remove this plate, you'll see a bit of rubbing wear due to friction of the plate shifting on the frame (especially on the surface of the frame around the front and rear fastener holes). Retaining the rubber transmission mount will provide a bit of compliance, since the powertrain is connected to the frame ladder at 3 points, such that a far worse condition would be a solid transmission mount which would then triangulate the frame. The old school drag racers ran with a solid mounted engine plate, but since the plate is vertical, it can accomodate some flex in racking. There will always be some frame racking and twist, hence my babbling about the engine mounts in which a poly or rubber mount provides some compliance between the flexing frame and the stiff engine block.

Best regards,
Mike

 

[eucharistos]

the technical aspect of this discussion is already beyond me, but

is that a fram oil filter in pic 2

 

[AndyMac]

eucharistos - yes, that is a fram filter, previous owner must not have liked the car very much, lol. You wouldn't believe the amount of loose bolts I've found so far. His mechanic was "the ****".

2000_Black_RT10 - Thanks Mike, that is a very technical and eye opening explanation. I like feedback, especially when backed up by some actual knowledge. I had no idea what the plate was for under the tranny either, although I suspected it was just a skid plate. I did see a member with a mid plate attached to the lower portion of the exposed bellhousing bolt holes around here. Like the solid tranny mount, I imagine it would amplify the problem more than help it. Maybe stock mounts and a mid-plate that allowed the frame rails to rack, but prevent the motor from twisting..

I have lots to chew on now, thanks!

 

[Madduc]

You really asked if JonB has ever been in a Gen I? Oh boy...............

 

[AndyMac]

You really asked if JonB has ever been in a Gen I? Oh boy...............

It was meant to be a joke, geared more towards the fact that the Gen1 is rough to begin with, not that Jon has never been in one. I know who he is, and I meant no disrespect to him.

Later,

 

[JonB]

None taken! But I did contemplate a snippy retort or two as I fiddled thru photos from my 92, 93, 95x2, VOI 1-2-3 (all Gen 1) etc....

Something like: "I have 3x more track days in Gen 1 than he has posts" .... but I skipped it

 

[Dom426h]

I definitely would not recommend using solid mounts, the chassis does flex torsionally (and the Viper suspension is quite stiff) and it also racks, the engine block is very stiff, something will fatigue over time with use.. just give it some time.. something is going to crack..

+1

seems to me as though this would be common sense to most...

 

[AndyMac]

Jon - Ha, that would have been a good one!

Dom426h - Yea, Mike brings up some interesting points that you would have thought would be obvious.

 

[plumcrazy]

Good info in this thread.

I'd listen to 2000_black rt10

 

[Madduc]

It was meant to be a joke, geared more towards the fact that the Gen1 is rough to begin with, not that Jon has never been in one. I know who he is, and I meant no disrespect to him.

Later,

Gotcha! My bad.

 

[2000_Black_RT10]

You're too kind Plum.. Hey Andy, I found a few minutes and quickly modeled an example for you to illustrate stress in your design.

Mind you this is not fully representative of an assembly.. but with a rigid portion of the engine block at the top and a rigiid protion of the frame, basically illustrating how the U bracket is impacted and the open box mount may react. I only spent about 20 minutes or so compiling this little demo.. no worries if not worth much.. In both cases, you can see stress rise where your welds are. Displacement is exaggerated just to show the direction of how they deform, but flexing even at very small values back and forth a thousand times and more, the steel and aluminum will fatigue and start to crack.

The CAD model..

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Stress if the mount twisted due to frame racking.. (* exaggerated displacement for illustrating motion of deformation)
Stress video: http://www.wincom.net/mnllehti/Frame_Racking_Stress.wmv

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Stress if the frame twisted / engine torque, pulling the mount apart.. (* exaggerated displacement for illustrating motion of deformation)
Stress video: http://www.wincom.net/mnllehti/Frame_Twist_Stress.wmv

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[eucharistos]

that's cool

 

[2000_Black_RT10]

I wonder how they'll SOUND ? Their actual name is "Isolators".....wont be any now!

In engineering we can just call them mounts, here's an example work that I was involved / working at (Daimler)Chrysler.. (my name is in the doc too).. It's a large PDF.. takes a few minutes to load.. but it is an example of how complicated things can get..

Glad you enjoyed it eucharistos

Link Powertrain mount development - PDF