[JSPONT]

Just saw George's post, he beat me to it. Thanks George.

[grandville455]

Thanks George, Since i'm planning on doing a front n mid plate i'll be watching this thread too, I got some great pics from Janderson and his bird he did!

[JSPONT]

Originally Posted by grandville455

Thanks George, Since i'm planning on doing a front n mid plate i'll be watching this thread too, I got some great pics from Janderson and his bird he did!

I got a photo from Billy C ( that bad azz purple GTO) with the engine out and the mid plate set up. Looks simple to me.
They are shipping the mid plate by the end of the week. I'll have the plate before the tranny is back.
I post some photos as I go. I got some good advise on the install from Bob and Frank.

[grandville455]

Originally Posted by JSPONT

I got a photo from Billy C ( that bad azz purple GTO) with the engine out and the mid plate set up. Looks simple to me.
They are shipping the mid plate by the end of the week. I'll have the plate before the tranny is back.
I post some photos as I go. I got some good advise on the install from Bob and Frank.

Awesome, Look forward to it. I think the front and mid plates themselves look pretty easy to do, its fabbing up a mount for the for and aft arms that bolt to the block and someplace solid for the mount itself
,More then likely i'll do something like Jesse did on his 78.

[Rob B]

When I built my fore/aft bars for the plates on my car, I bought a rod end kit from this company and a piece of tube to make my two bars. Cheaper than buying an actual "kit" from some of the other vendors.
https://www.qscomponents.com/collect...nd-4-link-kits

[taff2]

I use 1/4" thick T6 ali for my mid plate and front motor mounts, this material is very stiff. For engine locators I used two short lengths of 1" steel tube with the ends flattened and drilled, angled forward from the block and down to a pair of small brackets on the chassis tube, keep it simple is my motto.. Been in the car nearly 10 years without a problem. A mate of mine used 1/4" thick steel for a mid plate without locators, it cracked within 2 years from the front to rear flex.

[gman005]

Make sure to check that dowel pins fit in plate before you try and install the motor. Ask me how I know. lol

[JSPONT]

Originally Posted by gman005

Make sure to check that dowel pins fit in plate before you try and install the motor. Ask me how I know. lol

LMAO!! I have the motor and tranny out so I can do that easy. Thanks for the tip!

[GTO Dan]

I only use a single front to rear bar, is there really a need for two?

[v869tr6]

The two mid plates that I am using have a built in flex plate shield, they take some work but I like the safety.
https://butlerperformance.com/i-2445...html%3Fq%3Dtci

[GTOGEORGE]

Originally Posted by GTO Dan

I only use a single front to rear bar, is there really a need for two?

I only have a single bar in back on BOTH (passenger & driver) sides.


GTO George

[Kevspontiacs@aol.com]

I haven't seen anyone metion the trans mount. With front mounts and a midplate shouldn't the bolt be removed from the trans mount to eliminate stress on the case? Especially in a factory framed car that is going to flex?

[JSPONT]

I think I get more frame flex with out the mid plate. My left motor mount and chain wants to take the left rail and flip it over.
The mid plate will mount further back on the down side of of the rails. there is less side to side movement there than where the motor mounts are. At least that whats my head tells me.
If someone can has experience with that, please fill us in. I have a poly tranny mount.

[Robert C.]

Frame flex comes from the rear axel and the twisting motion of the drive shaft trying to lift the car. The control point is the motor mounts. That is where its power starts the energy of motion. By adding a mid plate the control point is moved to the mid plate and off the motor mounts. Less stress on a stock block.

Ever run a motor on a engine stand and smack the throttle and have it flip over? No.

Frame flex starts from the back. The mid plate helps comtrol the twisting of the frame at mid car. The front motor plate works the same way.

The transmission rear mount should be rubber mounted in a stock frame car. You can't have 100 percent no flexing on a stock frame car.

Adding solid body mounts ties the body in to the frame. It adds more support to keep the twisting motion from starting. So changing these out is one of the first steps to control frame flex.

There was a smart guy long ago that stated: (Every action has a equal and opposite reaction.) Isaac Newton I think.

You stop frame flexing at the rear and work it to the front.

You adjust your slapper bars so I believe the driver side to hit first to counter the twist.

A weak mid plate only supports the motor. A steel mid plate helps to control the twisting motion. It's like a big X in the frame.

Front to back movement comes from the weight of the motor and transmission going back at launch and the cars stopping motion. Anytime a object starts a motion it contains energy. Best not to let it start.

Night night.

[Robert C.]

One other thought.

If you have a race car with a stock frame and it will never be a real street car again you can do this.

Add a mid plate and a strong front plate set up and cut the center frame support out under the oil pan. It is not needed to go stright. Only needed if you road race or want more support in a crash.

Anyone cut it out and weigh it?

[JSPONT]

Originally Posted by Robert C.

Frame flex comes from the rear axel and the twisting motion of the drive shaft trying to lift the car. The control point is the motor mounts. That is where its power starts the energy of motion. By adding a mid plate the control point is moved to the mid plate and off the motor mounts. Less stress on a stock block.

Ever run a motor on a engine stand and smack the throttle and have it flip over? No.

Frame flex starts from the back. The mid plate helps comtrol the twisting of the frame at mid car. The front motor plate works the same way.

The transmission rear mount should be rubber mounted in a stock frame car. You can't have 100 percent no flexing on a stock frame car.

Adding solid body mounts ties the body in to the frame. It adds more support to keep the twisting motion from starting. So changing these out is one of the first steps to control frame flex.

There was a smart guy long ago that stated: (Every action has a equal and opposite reaction.) Isaac Newton I think.

You stop frame flexing at the rear and work it to the front.

You adjust your slapper bars so I believe the driver side to hit first to counter the twist.

A weak mid plate only supports the motor. A steel mid plate helps to control the twisting motion. It's like a big X in the frame.

Front to back movement comes from the weight of the motor and transmission going back at launch and the cars stopping motion. Anytime a object starts a motion it contains energy. Best not to let it start.

Night night.

Great info, Thanks Bob. My car is 99% street car. Otherwise I would love to get rid of the cross member. I know a lot of guys on the street cut them and add a moly tubular bar across.

I guess I should think about a drag bar in the rear end. Spohn makes a nice one. It ties the rear to the frame rather than the control arms and instead of the "A body twist launch", it brings the car up straight.
Another winter project added.
So my car will ride like a truck LOL

[RA462]

Things are not finished in the picture but this the best I can find right now. I made my own steel 1/8" mid plate bolted to 1/4 brackets welded to the frame. I also made a removable cross member. Also notice I cut the top part of the cross member down to aid header installation. A G-Body like mine needs all the help it can get when installing a Pontiac engine. One piece of advice is don't bolt the mid plate in backwards. It makes installing the starter much more difficult.

[Robert C.]

Originally Posted by RA462

Things are not finished in the picture but this the best I can find right now. I made my own steel 1/8" mid plate bolted to 1/4 brackets welded to the frame. I also made a removable cross member. Also notice I cut the top part of the cross member down to aid header installation. A G-Body like mine needs all the help it can get when installing a Pontiac engine. One piece of advice is don't bolt the mid plate in backwards. It makes installing the starter much more difficult.

That is what I am talking about. Good job!

[grandville455]

Originally Posted by RA462

Things are not finished in the picture but this the best I can find right now. I made my own steel 1/8" mid plate bolted to 1/4 brackets welded to the frame. I also made a removable cross member. Also notice I cut the top part of the cross member down to aid header installation. A G-Body like mine needs all the help it can get when installing a Pontiac engine. One piece of advice is don't bolt the mid plate in backwards. It makes installing the starter much more difficult.

Looks good! That's basically what I'm gonna do with my bird too, even tho its street driven, need room for the diaper etc. where are u gonna mount your brackets for your for and aft bars?

[janderson]

Originally Posted by 535 tall deck

I haven't seen anyone metion the trans mount. With front mounts and a midplate shouldn't the bolt be removed from the trans mount to eliminate stress on the case? Especially in a factory framed car that is going to flex?

Stock front sub frame w/front plate, mid plate, poly trans mount.