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Discussion Starter #1
I am just wondering what your thoughts are with solid mounting motor and trany in a full tube chassis. The reason for this ? is we have very tight limits with room on our new rig we are building. What do you see as pros and cons? The drivetrain specs are Northstar, 700r, Atlas II 3.8 with 16" swayaways on each corner. We are trying to keep the COG as low as we can in the chassis and solid mount would allow for 1-1.5" lower without the loss in clearence.

Thanks

Nick
 

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If you solid mount to the original mount locations on a Northstar block and your chassis flexes at all, you are going to put a huge strain on the die cast aluminum block. I would think you would take a good chance at breaking the block. When you solid mount, you are turning your motor into a structural member in your chassis.
 

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Just an idea....

Put the poly part of the mounts up top, over everything (like a hanging basket). If your building a buggy I'm sure you can fab up the clamps or brackets to hang the tranny/t-case so you can leave the belly higher without the actual mounts underneath.
 

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You could solid mount it NASCAR style. They use a plate that bolts behind the engine accesories and then bolts to the chassis. It spreads the load over the entire front of the block. I've been considering this myself.

Easy
 

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by first thought was sure why not, but alum. caddy engine, thats an immediate NO !!!

maybe if you fabed the solid motor mount (ie middle piece) with some thought to it bending or deforming if it needed to, you could do that safley....

What do the stock mounts look like? Can you retro on some poly leaf bushings on a new middle mount piece...

got any pics??
 

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Discussion Starter #7
Big Dude that is a good idea that has not crossed my mind.

Easy, if that is what we do that is how we plan on doing it.

I am wondering the pros or cons such as torq lift due to the solid mounts or like was stated before, if I take a hard roll without the chassis being very ridged what would happen.
 

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Pros: low profile, nothing moves (so you can run items REAL close to the motor and rotating parts), cheap and easy

Cons: NVH (noise, vibration, & harshness) I cannot stress this point enough. If you want to be able to comfortably hold a conversation with your spotter or keep your filligs in place, find a way to put some sort of rubber mount in there.

cmk
 

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Discussion Starter #9
I know all about NVH. I have a 1970 impala that i draged and it was solid mounted. You couldn't even hold a can of pop in the damn thing without spilling. I am willing to live with this a strick comp. rig but my main concern is when you torq the motor it will inturn try to unload the drivers side. I am worried that when on a steep climb and hard on the gas it will want to roll the rig over. Maybe a stiffer rate on the passenger side???
 

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XtremeEngineering said:
I know all about NVH. I have a 1970 impala that i draged and it was solid mounted. You couldn't even hold a can of pop in the damn thing without spilling. I am willing to live with this a strick comp. rig but my main concern is when you torq the motor it will inturn try to unload the drivers side. I am worried that when on a steep climb and hard on the gas it will want to roll the rig over. Maybe a stiffer rate on the passenger side???
With coil-overs, spring rates could be adjusted on all four corners, correct?
 

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ask dustin webster from redbull how he likes his solid mount set up. last i heard he is breaking trannys when the chassis flexes.
 

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cmk said:
Pros: low profile, nothing moves (so you can run items REAL close to the motor and rotating parts), cheap and easy

Cons: NVH (noise, vibration, & harshness) I cannot stress this point enough. If you want to be able to comfortably hold a conversation with your spotter or keep your filligs in place, find a way to put some sort of rubber mount in there.

cmk
I've got my engine and tranny solid mounted... can't say i've noticed much diference in vibration... If you did'nt know it was solid, you wouldn't guess that it was....

It is more responsive... no drivetrain 'windup' on small blips of the throttle, the torque that would have nomally wound-up the drivetrain is sent straight to the tires...

I do have to tighten various nuts & bolts on a regular basis....
On most things I've lock washer'ed, lock tighted, and lock nut'ed them...

As far as hammer down full torque effects on climbs....
Even the rubber & poly mounts will only flex so much then the twist is transfered to the frame.....
 

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Discussion Starter #13
Yes you can adjust on all four corners but say for example you have 170 over 200 in the rear and 200 over 200 in the front you would run a little stiffer coil on the passanger side. See what I mean??

I do agree that you have wind up with mounts and that intern will absorb most of the shock. That is why I feel a solid mout would be so much harsher during a hard lanch. With the rubber it will absorb all that suden impact and being solid it will transfer it instantly.

Camo, I have heard about that and trust me when I say that this tranny is alot more ridged.

What about rubber motor mounts and solid tranny or vice versa.
 

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XtremeEngineering said:
my main concern is when you torq the motor it will inturn try to unload the drivers side. I am worried that when on a steep climb and hard on the gas it will want to roll the rig over. Maybe a stiffer rate on the passenger side???
This effect will be exactly the same whether you run solids or flexible. The torque from the motor/gearbox is always reacted by the frame which in turn lifts the suspension on one side and compresses it on the other. Its the torque thats going down the DS that causes this. Stiffer springs will lesson the movement (springs twice as stiff will halve the motion) or lower diff ratios (ratio twice as low will halve the motion) can help.


Sam
 

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Discussion Starter #15
Good point Sam.

Where I am getting this worrie from is there is a notable difference in lean in my Impala when the motor was solid then when it was mounted with stock mounts. The only time you would notice it more is when you would flash the converter of run the transbrake. That sudden lanch was way more violent. It felt as if it was planting the tourqe that much harder
 

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Why not use a mid plate bolted to tube through some rubber pucks and a regular trans mount. I had a mid plate in my previous rig for a little while, but junked it before I fired it up. Nice part about a mid plate is you can use it as your firewall and/or an adapter if you wanted to run a powerglide. That assumes the mid plate alone would be enough to hold the engine.
 

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heep86 said:
solid motor mounts are going to play hell on you kbnock sensor if you are injected
No problem there either.....

I've had people tell me that my 76 Heep would fall apart if I solid mounted the engine/tranny... Of coarse they were just speculating and hadn't tried it themselves....

I try to be conservative with the skinny pedal, so I'm not familiar with its full throttle launch characteristics...
but when crawling, when you need a little bump to make it over a rock to maintain your momemtum the response is instant,,,


As far as the idea of solid mounting one and not the other... Seems to me you want them twisting or solid together..else you will be putting alot of stress on your bellhousing, with one part of your drivetrain twisting and the other not...
 

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Discussion Starter #19
Whats weird is that I have seen alot of race guys that run solid motor and rubber tranny. But never the other way around. I do agree with you. I think I may just change a bit on the chassis so that I can get normal mounts
 

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XtremeEngineering said:
What about rubber motor mounts and solid tranny or vice versa.

I have snapped 2, NP435 trannies, completely in half, just from bind, caused by contact with the tranny crossmember. I finaly had to clearance the crossmember and tranny buy about 1/2" to solve the reoccurring problem.
 
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