[Tim Corcoran]

In a door car what is better a front plate only or both a front plate and mid plate?

[Dragncar]

I can,t say for sure but I am running a mid plate with elephant ears for the front of the engine along with Mighty Mounts for for and aft play.
Just running the Mighty Mounts with the elephant ears worked for years.

[firechickenman]

I believe "better" would be front and mid plates. It takes all the twisting force away from the block. I've been running solid motor mount and a rubber trans mount for years. I feel like I've outgrown that and am going with a front and mid plate when mine goes back together.

[gman005]

I use both.

[Dave Polichena]

Both without a doubt. Having a mid-plate keeps the trans in place when pulling the motor or the other way when pulling the trans.

[Elarson]

Both! The mid-plate does most all of the severe work. To run some numbers...if your engine makes 600 ft-lbs torque and you have a first gear of 2.43, then the driveshaft torque is 600x2.43= 1458 ft-lbs. Every reaction has an equal and opposite reaction. The transmission case has to be restrained from 1458 ft-lbs of counter-torque. A mid-plate sends those forces to the chassis instead of letting them twist the block. The front plate mostly just helps hold the dead load of the front of the engine.

Eric

[Half-Inch Stud]

This ^^^^^ passed physics. Static and Dynamic Mechanical Stress can be analyzed like that.

[charlie66]

I think if you had just the mid plate it would be a big up grade from just the motor mounts . IMO it does more then the front .. I have a mid plate and solid motor mounts and it seem to be holding up fine.. Both would be better of course but for me it was easier because of the belt & pulley and exhaust changes that would of had to be done.. I have forward facing headers ..

[grandville455]

Both! do it once and be done, don't forget you'll need the converter reworked for the mid plate also, which isn't a bad thing to have it looked at

[blueghoast]

I run both on my tempest and I made my mid-plate that bolts
on the out-side of the bellhosing, I made two 1 for the blow proof
with a stick and 1 for the automatic. If you run a mid-plate
that go's between the block and trans you can use spacers for
the torqe-converter the same thickness as the plate.
And I always use 7/16 bolts for my converter to flex plate bolts.

GT

[Tim Corcoran]

I already have both a front and mid plate I see some run a front plate only and was wonder why. Thanks for all the responses.

[Tom Vaught]

Even when the Pontiac Engineers (on the older cars, (pre-1960)), used a single front engine mount that bolted in front of the timing cover there was some movement allowed.

Might "work" for a while, maybe, on a rigid front block mount before it cracked the block behind the # 2 Main Cap on the block.

Tom V.

[Tim Corcoran]

Back in the 60's Oldsmobile on their 371/394 engine only had a single motor mount on the front of the engine and two mounts on the transmission supporting the engine. On a passenger car some designs were good enough for a driver but not adequate when adding substantial power to the engine. Kind of like separating motor mounts that would never brake if the original power level was not increased and not hot rodded.

[lust4speed]

As wimpy and flexible as our A-body frames are I wonder whether the plates add support to the block or do they stiffen up the frame using the stiffness of the block?

12 point cages being the exception to flexible frames since they nicely stiffen things up.

[Tom Vaught]

More than one roof car (A-Body) had a convertible frame under the car.
Street racing application.

JS

Tom V.

[Tim Corcoran]

Yeah good point, my frame is pretty much rubber I wish I had a convertible frame to put under it. If by some miracle my new engine combination puts me into the 9's then I will have to cage it and put in a window net which I don't want to do but a cage might stiffen up my frame some.