chassis stiffening along inside longs

[BGman]

I read an old post that recommended welding 3" el stock along the inside top corner of the longitudinal. I pulled back my carpet- this would be pretty easy to do and would remain hidden when the carpet goes back.

Anyone tried it? Is this an area that needs re-inforcement if the longs are structurally sound to begin with?

[maf 914]

BGman,

You might want to read these two threads from the 914club. They are related to your question.

Then do a search there for "stiffening kit" and you will find more posts discussing the topic.

http://www.914club.com/bbs2/index.php?act=ST&f=2&t=4702&hl=stiffening+kit&

http://www.914club.com/bbs2/index.php?act=ST&f=2&t=4544&hl=stiffening%20kit&st=0

Mike

[Bleyseng]

To do it right, you need to remove the lower cover to get to the firewall. This corner is where you install the brace, at the firewall and long.

The general concenus is the stiffining kit is a waste of time.

Geoff

[BGman]

Geoff-

You are saying to weld a piece in the interior that ties the long to the firewall more securely?

What lower cover are you talking about?
-g

[Bleyseng]

Remove the backpad and look at the bottom of the firewall. Hmm, there is a piece of cover or inner firewall cover so you can't actually see the bottom of the firewall. Remove it and then you can see the bottom corner where the firewall and the long are connected. This is where the car flexes and a corner brace really helps. use 16 gauge and tie the long and the firewall together like the stiffening kits are made. Puddle weld in the holes and the edges. Replace the cover piece.
On the drivers side watch out for the ebrake.

If you look at the car, the pan, firewall, and the longs all join here and can be like a moment point for the car. Stiffening here really helps to connect these panels together.

Geoff

[BGman]

Thanks Geoff, I will look into it.
16 guage is good enough? It is just as easy for me to weld in 1/8", probably easier with my welding skills (HA!)

Mike, I read the links that you included. Wow! There are some really extensive roll cage designs shown. I don't think I am at that level- although I really liked the diagram shown at the end by Brad Roberts of the piece welded onto the top of the firewall in the engine bay...and then downtubes to the rear of the car.

The diagram did not show exactly how/what the downtubes were actually attached to (eluded to shock towers) - but it was a clean (hidden) looking design.....something that I would be willing to consider.

[Zeke]

Originally posted by Bleyseng


The general concenus is the stiffining kit is a waste of time.

Geoff

To me, rear top shock mount is cantalevered back from the strength of the car. This point takes most of the bump force with the console taking the torsional force.

Your point below about the firewall junction makes sense, but ingnoring the rear does not. Especially since the trans mounts are even further back in the structure. Why would the concenus be that the stiffening kit is a "waste of time?"

[sean_V8_914]

the car I did felt much tighter. no it was not rusty (not structurally compromised by corrosion)

[Bleyseng]

Zeke, as you say, the rear shock towers are a point of flex. The inside panel joint where several pieces meet is where the cars crack. Getting to this point to reinforce is very hard. Brad R has shown pics on the other BBS.
The stiff kit doesn't do much to address these problems.
The more you stiffen up the car the more the other problem areas show up ie crack! Most of these cars are not welded enough either, count the spot welds. Big sticky tires, stiff springs, stiff shocks transfers load to lots of places beyond what the engineers ever figured.

Geoff

[maf 914]

My intent for the reference to the attached links was not to illustrate roll cage design (which was the initial topic in these threads), but to point out the discussion of reinforcement of the inside of the longitudinals and the rear firewall. In one of the threads Brad describes welding in steel reinforcements along the inner longs, from the front firewall to the back firewall, then around and across the rear firewall. Similar to what Geoff has described I think. I'd like to see a car that has had this mod.

Mike

[sean_V8_914]

[no substitute]

Originally posted by Bleyseng
Remove the backpad and look at the bottom of the firewall. Hmm, there is a piece of cover or inner firewall cover so you can't actually see the bottom of the firewall. Remove it and then you can see the bottom corner where the firewall and the long are connected. This is where the car flexes and a corner brace really helps. use 16 gauge and tie the long and the firewall together like the stiffening kits are made. Puddle weld in the holes and the edges. Replace the cover piece.
On the drivers side watch out for the ebrake.

If you look at the car, the pan, firewall, and the longs all join here and can be like a moment point for the car. Stiffening here really helps to connect these panels together.

Geoff

Are you speaking of an area inside the cabin behind the seats?

[Bleyseng]

yes

[BGman]

I think I will take the same topic over to the 914club site - it is still very preliminary....will see what the guys that contributed to the thread that Mike attached still say.... (actually, I have only learned recently of the 914club BBS)
-g