Isolating Motor plate vibrations?

Hello all,

I've searched the posts here and can't seem to find a post were someone addressed this issue previously.

I have a 57 Chevy 3/4 ton long bed truck. I've shortened it to a short bed length by removing 8.25 inches from the area just behind the cab.
The frame is made from 3/16th steel, so I have had some 3/16th plate channel bent to slip inside the inner dimension of the factory frame. I plan on welding the inner channel in place the full length of the frame rails to box or stiffen the rails. I will also be building a X-Member to prevent racking or twisting of the frame. I really like the benefits of the motor plate system boxing in the front over hang. The front over hang will get a IFS coil setup from No Limit Eng., the rear over hang is getting a No Limit Eng. Fat Bar 4 Link coil over setup with a 9" rear end. The motor of course is going the be a 532 BBF with a C6 behind it. The motor plates will hopefully offer some engine adjustment and some room for header fitment too. I'd like to find a off the shelf set that might just bolt on.....

I'm a little concerned with engine vibrations. I can isolate the cab and it's mounts of course. I'm not looking for a Lincoln type of ride. I just am wondering what I can do to abate or minimize interior vibrations/noise. I know it's going to be loud.



My wife and I would like when done, to take the truck to the Tri Five Nationals and make a couple passes there, and then latter on use it for car gatherings, hauling the drag boat to the lake, etc.  This will be a pump gas deal with maybe a little spray when needed.

Any ideas are welcomed on killing some vibes.

Thanks..

Art

Having to make the compromise choice between "street use" ride quality vs optimum "strip use only" design always sucks.

Most anything you do to reduce a large portion of the motor plate, mid plate, and travel limiter vibration reaching the chassis (like some form of rubber mounting) is in effect going to reduce the rigid structural benefits of using this engine mounting method in the first place.

You could try mounting the motor/mid plates with a piece of thick rubber (or urethane) between the plates & their mounting tabs/seats/saddles. But the bolts used at these mounting points are usually mounted horizontally in single shear loading. That means the thicker the rubber/urethane you use the greater chance you have of a fastener failure, or bending the plates and/or their mounting brackets from side loading or rotational torque loading as the rubber/urethane "squishes" around.

You could also try mounting the sides of the motor/mid plates to the chassis sitting on a vertically mounted bolt & rubber/urethane "doughnut" assembly. This mounting method's main bolt is still being mounted in single shear, but since it's mounted vertically it won't be as effected by engine rotational torque loading. But again you lose the structural benefits of rigid mounting the plates.

If this project is in effect going to be a "Pro Street/street rod" type combo (that will actually see a decent amount of street/highway miles) IMO it might be a better idea to just go with conventional OEM/factory style mounts instead of the motor plate/mid plate/travel limiter method.

I think Dave's right. In this case, trying to get the best of both worlds will probably get you neither. If this thing is going to hook hard, go with the solid plate system and get a better stereo to drown out the noise and vibes. If it's a cruiser, I'd do the rubber biscuit deal at the frame rails.

Btw, at the TriFive Nationals a 532"Ford will NOT make you lots of friends.

Would they even let it in?

maverick wrote:I think Dave's right.  In this case, trying to get the best of both worlds will probably get you neither. If this thing is going to hook hard, go with the solid plate system and get a better stereo to drown out the noise and vibes. If it's a cruiser, I'd do the rubber biscuit deal at the frame rails.

Btw, at the TriFive Nationals a 532"Ford will NOT make you lots of friends.

I'd just hangout and checkout all the cool rides, and leave the hood closed. Until it has to go through tech.

Mike R wrote:Would they even let it in?

Sure they will, I'll dress the part, BowTie cap, jacket, etc. The real problem is tech inspection, I can see it not passing tech. That should go viral on the web.

It's no "A" head deal so we are there just have fun and spread some Ford love!

DILLIGASDAVE wrote:Having to make the compromise choice between "street use" ride quality vs optimum "strip use only" design always sucks.

Most anything you do to reduce a large portion of the motor plate, mid plate, and travel limiter vibration reaching the chassis (like some form of rubber mounting) is in effect going to reduce the rigid structural benefits of using this engine mounting method in the first place.

You could try mounting the motor/mid plates with a piece of thick rubber (or urethane) between the plates & their mounting tabs/seats/saddles. But the bolts used at these mounting points are usually mounted horizontally in single shear loading. That means the thicker the rubber/urethane you use the greater chance you have of a fastener failure, or bending the plates and/or their mounting brackets from side loading or rotational torque loading as the rubber/urethane "squishes" around.

You could also try mounting the sides of the motor/mid plates to the chassis sitting on a vertically mounted bolt & rubber/urethane "doughnut" assembly. This mounting method's main bolt is still being mounted in single shear, but since it's mounted vertically it won't be as effected by engine rotational torque loading. But again you lose the structural benefits of rigid mounting the plates.

If this project is in effect going to be a "Pro Street/street rod" type combo (that will actually see a decent amount of street/highway miles) IMO it might be a better idea to just go with conventional OEM/factory style mounts instead of the motor plate/mid plate/travel limiter method.

Dave thank for the sage advice!

Here's a dumb idea I have rolling around in my head on the urethane mount deal.

How about I take two pieces of steel plate 5/8 or 3/4 thick, maybe thicker. I deeply machine out a two sided rectangle shape in each plate, creating a "L" shaped ridge into the steel plate, that the motor plate could lock or fit into. The passenger side frame/steel plate would have the short leg of the "L" at the bottom to support the motor plate when bolted in. Now on the driver side I place the short side of the cutout "L" on the top. Both short legs cut into the steel plate would act as a rotational  stop or limiter of the motor plate. Why do this?

I like to machine a piece of urethane to act as a backing pad while also incorporating a lip to go between the top and bottom of the motor plate to cushion or dampen vibration as the motor rotates slightly into the steel machined "L". Hopefully the "L" stop would lessen the sheer loading on the fasteners.  The fasteners to assemble the motor plate would need to be oversized to deal with the sheer loads. I'm thinking 5/8 dia or better using no threads through the aluminum plate bored holes, only the uncut or smooth part of the bolt.

I can think of a number of variations to this design. I could weld something together simpler than this to make it lighter and more feasible.  

Sound dampening would be limited at best, hopefully better than a solid bolted down deal.

Sound like a dumb idea?

Art

XF-66 wrote:.........idea I have rolling around in my head on the urethane mount deal.....

Heh, you're going to have to post a pic of a concept drawing of this because the few remaining ancient brain cells I have left just locked the F up trying to picture this mounting idea you have described.

DILLIGASDAVE wrote:

XF-66 wrote:.........idea I have rolling around in my head on the urethane mount deal.....

Heh, you're going to have to post a pic of a concept drawing of this because the few remaining ancient brain cells I have left just locked the F up trying to picture this mounting idea you have described.

Lol!
I hear you brother, the gray hair won't stop coming! Along with a bunch of other BS that goes along with aging....  

I drew a quick drawing of my idea. A drawing of the opposite side would have the Stop/Ledge lower or reversed of the drawing I made. This would effectively lock/limit the rotation of the motor plate while the urethane would cushion the hit. The urethane would need to be no thicker that .250 to keep things tight and in alignment.

Mount

XF-66 wrote:Mount

There will still be vibration transfer since the head of the bolt, the bolt body, & the nut are still in direct contact with the motor plate & mounting bracket. Isolating the bolt head/body & nut from the motor plate & bracket would further dampen vibration transfer, but could also increase plate movement.

Also with this design a "C" channel bracket might be a better idea vs an "L" bracket reversed each side. This is because both sides of a motor plate really need to be sitting on something (like a motor plate seat/saddle, or frame rail) vs having the mounting bolts doing all the work holding the motor plate/engine up.

I'd get the truck up and running, see if there will be to much vibrations. You might not have an issue. I had a plate in my mustang, it wasn't bad. I wouldn't hesitate to use another motor plate on the street.

Jess

DILLIGASDAVE wrote:

XF-66 wrote:Mount

There will still be vibration transfer since the head of the bolt, the bolt body, & the nut are still in direct contact with the motor plate & mounting bracket. Isolating the bolt head/body & nut from the motor plate & bracket would further dampen vibration transfer, but could also increase plate movement.

Also with this design a "C" channel bracket might be a better idea vs an "L" bracket reversed each side. This is because both sides of a motor plate really need to be sitting on something (like a motor plate seat/saddle, or frame rail) vs having the mounting bolts doing all the work holding the motor plate/engine up.  

I agree!
I just figured that minimizing the surface contact area of the motor plate/frame mount with urethane would help deaden a majority of the vibrations transmitted. Increasing the bolt diameter would also increase contact area as well, (thus transmitting more vibes too) and limiting the flex or slippage between the plate and the mount.

I had thought of the "C" type of mount trapping the plate and even a U shaped for the plate to slide into, but never consider letting the motor plate rest on the mount or frame rail. I figured it needed to be pinned in place through the fasteners. I'll head back to the drawing board as the say! Thanks for your advice and experience!!

Mustang-junky wrote:I'd get the truck up and running, see if there will be to much vibrations.  You might not have an issue.  I had a plate in my mustang, it wasn't bad.  I wouldn't hesitate to use another motor plate on the street.

Jess

Like you mentioned, think I'll try it out first and see what I have to deal with. I know I can also work on the cab mounts to aid in noise transfer too. Aluminum has to be a much better choice than a steel plate when it comes to transmitting vibrations from the engine to the frame rails.

Thanks...

Mustang-junky wrote:I'd get the truck up and running, see if there will be to much vibrations.  You might not have an issue.  I had a plate in my mustang, it wasn't bad.  I wouldn't hesitate to use another motor plate on the street.

Jess

I agree..  If you're the type of car guy to consider putting a motor plate setup together, the resulting "vibrations" probably aren't nearly a problem to you.

Too many over-think the "vibration problem", kind of a internet lore in itself.  Unless your ride is a rattle trap already, solid mounting is no big deal.  I solid-mounted my '85 Mustang, subframe connectors, 8-pt bar, and it didn't seem any different than stock.  Except the huge increase in power

Any pics of this monster??