Solid Motor Mounts ???
Thread Starter
Race Director
Joined: Mar 2016
Posts: 14,320
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From: Napa Valley California
Solid Motor Mounts ???
I'm planning to use solid motor mounts on my 73 with the 496 cu in motor I'm building.
I've heard negative things about using rubber mounts with the amount of torque my motor will be putting out and negative things about poly mounts breaking down when subjected to heat.
Are there any negatives in using solid mounts or problems I need to know about?
I plan to install the 73 OEM style rubber body mounts which will absorb most of the vibrations in the chassis with the solid motor mounts.
There are several manufactures of solid motor mounts for C3's and I was wondering what brands are the best?
I've heard negative things about using rubber mounts with the amount of torque my motor will be putting out and negative things about poly mounts breaking down when subjected to heat.
Are there any negatives in using solid mounts or problems I need to know about?
I plan to install the 73 OEM style rubber body mounts which will absorb most of the vibrations in the chassis with the solid motor mounts.
There are several manufactures of solid motor mounts for C3's and I was wondering what brands are the best?
Last edited by OldCarBum; Feb 26, 2019 at 12:06 AM.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
I have a solid mount on the left side of the motor and a rubber one on the right. I believe moroso is the brand of the solid.
no complaints from me about vibration being transferred to the cabin, but I do run side pipes so they may be drowning it out.
no complaints from me about vibration being transferred to the cabin, but I do run side pipes so they may be drowning it out.
Last edited by REELAV8R; Feb 26, 2019 at 12:20 AM.
Race Director
Joined: Mar 2018
Posts: 10,640
Likes: 2,111
From: Golden Colorado
You won't like them if you do any amount of street driving. Race car stuff only. They transfer all the NVH (noise vibration harshness) directly on to the interior. Put the rubber or poly mounts in but build a torque limiting device that only lets the motor lift a very small amount before stopping movement. I use a turnbuckle from the hardware store and replace one hook end with a bolt that goes through the frame and then hook the other end to a bolt in the head, the alt bracket or some other convenient spot that will stop torque over from the left. You don't have to worry about the passenger side at all. Just the lift on the driver side. 
Drifting
Joined: Aug 2015
Posts: 1,939
Likes: 477
From: NSW, Australia
C3 of Year Finalist (track prepared) 2019
I have solid Moroso mounts. With rubber body bushings and a well balanced motor, there is NO noticeable NVH problems as a result, and it has stiffened the front of the frame nicely. Make sure you use a compliant gearbox mount still, particularly with a factory cast bellhousing.
Burning Brakes
Joined: Jul 2018
Posts: 875
Likes: 289
From: LaFayette Georgia
C3 of Year Finalist (performance mods) 2019
St. Jude Donor '19
OldCarBum, I run Moroso solid motor mounts in my 74 coupe with a 383 and 4 speed. I didn’t notice very much difference if any from the rubber mounts. The solid motor mounts are used in conjunction with a spreader bar, I believe it really solidifies the front of the car, making the engine an integral piece of the chassis. Having said that, I do view this car as a performance vehicle and don’t have the expectations of a modern street car. I have no regrets about changing mounts. I view this modification as a personal preference, I like it, and they are relatively inexpensive so no worries if you don’t like them. Just my .02 
Eddy
Eddy
Le Mans Master
Joined: Aug 2017
Posts: 8,336
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From: Cool Northern Michigan
Moroso Solids, Grade 8 Bolts, drop of Loctite Blue, never look back.
Maybe a ever so slight tingle in the steering wheel. Hardly worth mentioning. It lets you know you no longer have 180 horse.
On the transmission mount however, I prefer some rubber there, so as not to get the tingle through the shift ****. And the rubber mount should take any vibes out of the driveshaft, U-Joints, etc.
Some of us older children still remember the GM motor mount breakage of decades ago. Not pretty when the whole engine tilted to one side.
Maybe a ever so slight tingle in the steering wheel. Hardly worth mentioning. It lets you know you no longer have 180 horse.
On the transmission mount however, I prefer some rubber there, so as not to get the tingle through the shift ****. And the rubber mount should take any vibes out of the driveshaft, U-Joints, etc.
Some of us older children still remember the GM motor mount breakage of decades ago. Not pretty when the whole engine tilted to one side.
Last edited by HeadsU.P.; Feb 26, 2019 at 10:00 AM.
Race Director
Joined: Mar 2017
Posts: 11,923
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From: Virginia
I have the Moroso solids, and both the Energy Suspension and rubber trans mounts, waiting to go in the car. A local garage quoted me $300- to do all three. I'm tempted to take them up on it, probably with the rubber trans mount.
My current mounts have failed. Nothing holds the engine from rotating except weight and the backup tabs.
My current mounts have failed. Nothing holds the engine from rotating except weight and the backup tabs.
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Burning Brakes
Joined: May 2013
Posts: 789
Likes: 129
From: Los Banos CA
We put the Moroso solid mounts in our 79, after my son broke two of the rubber mounts with an almost stock engine (Don't ask me how he managed that - I'm SURE they were just defective... 
). Didn't notice any extra vibrations at all.
). Didn't notice any extra vibrations at all.
Burning Brakes
Joined: Jul 2018
Posts: 875
Likes: 289
From: LaFayette Georgia
C3 of Year Finalist (performance mods) 2019
St. Jude Donor '19
I have the Moroso solids, and both the Energy Suspension and rubber trans mounts, waiting to go in the car. A local garage quoted me $300- to do all three. I'm tempted to take them up on it, probably with the rubber trans mount.
My current mounts have failed. Nothing holds the engine from rotating except weight and the backup tabs.
My current mounts have failed. Nothing holds the engine from rotating except weight and the backup tabs.
Eddy
Last edited by 74_stingray; Feb 26, 2019 at 10:18 AM. Reason: addition info
Pro
Joined: Jan 2016
Posts: 502
Likes: 103
From: Reno Nevada
My 73 had solid Moroso mounts with a lower HP 454 when I bought it. Before I tore it apart, I ran it a bit and there was no vibration that I could tell. Going back with a 488 in the 600hp range and I used Moroso solid mounts. Have not run it since the rebuild yet, but based on the initial feel I don't expect much if any vibration. Side benefit is the engine helps to substantially stiffen the front of the frame.
Thread Starter
Race Director
Joined: Mar 2016
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From: Napa Valley California
Thanks guys,
It looks like the Moroso solid mounts will be my choice.
I am planning to run the rubber trans mount supplied with my SST TH-400 to TKO-600 conversion kit bolted to my G-Force cross member.
Van Steel set me up with a spreader bar that is going to be a tight squeeze with the big block, but with running the dual Spal fans from DeWitts, I should have just enough room.
It looks like the Moroso solid mounts will be my choice.
I am planning to run the rubber trans mount supplied with my SST TH-400 to TKO-600 conversion kit bolted to my G-Force cross member.
Van Steel set me up with a spreader bar that is going to be a tight squeeze with the big block, but with running the dual Spal fans from DeWitts, I should have just enough room.
Last edited by OldCarBum; Feb 26, 2019 at 11:16 AM.
Thread Starter
Race Director
Joined: Mar 2016
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From: Napa Valley California
Thanks Jebby,
A couple people commented in this thread that they, like you, installed a solid mount on just the drivers side.
I understand why, but is there some type of significant advantage to only installing the solid motor mount to one side and not to both?
A couple people commented in this thread that they, like you, installed a solid mount on just the drivers side.
I understand why, but is there some type of significant advantage to only installing the solid motor mount to one side and not to both?
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,024
From: New Braunfels Texas
Because I am lazy....the passenger rubber mount was new and only acts as a “pivot”.....
A lot of stuff is in the way compared to the drivers side.....I may install it one day....but maybe that is why I have no vibration....it is rubber on one side...who knows!
Jebby
A lot of stuff is in the way compared to the drivers side.....I may install it one day....but maybe that is why I have no vibration....it is rubber on one side...who knows!
Jebby
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,024
From: New Braunfels Texas
Thread Starter
Race Director
Joined: Mar 2016
Posts: 14,320
Likes: 8,124
From: Napa Valley California
Moroso's web site states that a solid transmission mount must be used with solid motor mounts.
Any negative issues with running the solid trans mount?
"Solid Motor Mounts must be used in conjunction with Solid Transmission Mounts to prevent breakage of engine block and transmission case due to torsional stress"
Any negative issues with running the solid trans mount?
"Solid Motor Mounts must be used in conjunction with Solid Transmission Mounts to prevent breakage of engine block and transmission case due to torsional stress"
