Options to stiffen chassis 69 Firebird?

[kmart401]

What gearbox are you running? Thats one wicked ride!! Can't wait to see more pics of this one!

[Nativefx]

Originally Posted by kmart401

What gearbox are you running? Thats one wicked ride!! Can't wait to see more pics of this one!

Running a close ratio T-56 Magnum mated to a 9" floater rear end with 3.89 gears.

[jlwdvm]

We have similar taste...check this out: http://www.pro-touring.com/threads/1...rack-car-build

I have DSE subframe connectors and a Alston 8-point cage with solid body mounts. I have about 150 miles on the car so far. Shaking it down before paint...69 Trans Am scheme. Its extremely loud and fast. I think I'm just gonna fab up some aluminum door panels and a rear seat delete. Not gonna put windows in it to save weight and hassel. It will never see rain anyway!

[Nativefx]

Originally Posted by jlwdvm

We have similar taste...check this out: http://www.pro-touring.com/threads/1...rack-car-build

I have DSE subframe connectors and a Alston 8-point cage with solid body mounts. I have about 150 miles on the car so far. Shaking it down before paint...69 Trans Am scheme. Its extremely loud and fast. I think I'm just gonna fab up some aluminum door panels and a rear seat delete. Not gonna put windows in it to save weight and hassel. It will never see rain anyway!

It's been awhile since I came across your build thread! I'll have to check out your updates. Maybe it will help on a few other things I'm thinking about.

[David Pozzi]

The front of the subframe needs support more than the rear subframe does. The stock sub is terrible in torsion ahead of the firewall. The front sheet metal contributes to half the front torsional rigidity. jlwdvm, - If you do a roll bar or cage, I highly recommend adding a diagonal brace to the main hoop. SCCA requires it, and it's a main component of any good roll bar. It can be removable by adding some double shear brackets.

[Nativefx]

Originally Posted by David Pozzi

The front sub needs support more than the rear does. The stock sub is terrible in torsion. The front sheet metal contributes to half the front torsional rigidity. jlwdvm, - If you do a roll bar or cage, always add a diagonal brace to the main hoop. SCCA requires it, and it's a main component of any good roll bar.

Thanks David. Any advise on how I can better support the front sub? Would something like the Alston subframe connector cross braces help with this? I'm open to other ideas as I really don't think I want to put a cage in it. thanks

[David Pozzi]

I like braces that run from the firewall down to the upper A arm mounting points. Hotchkis makes these: http://www.hotchkis.net/product/1967...k=&yr=&md=&sm=
They are a bit more complex and heavier than I prefer.

Pro-Touring F body makes these for second gen Camaros but not first gen's. http://www.pro-touringf-body.com/cha...omponents.html

They are lighter and simpler but won't fit a first gen F body. Herb Adams invented this style and they stiffen the front sub by 1/3rd.

You could have some made up. The firewall on a first gen needs a doubler plate inside to spread the load and resist cracking if these are used.

I also tested a 69 camaro with full roll cage. The front braces went to the subframe kickup about 10" behind the upper A arm mounts. I was surprised it didn't stiffen the front sub torsionally any measurable amount.

I haven't tested the Chassisworks type underfloor braces. I'm sure they do good things, but ground clearance is usually so tight, I'd be worried about clearance. They won't help the area ahead of the firewall at all.

[jlwdvm]

Originally Posted by David Pozzi

The front of the subframe needs support more than the rear subframe does. The stock sub is terrible in torsion ahead of the firewall. The front sheet metal contributes to half the front torsional rigidity. jlwdvm, - If you do a roll bar or cage, I highly recommend adding a diagonal brace to the main hoop. SCCA requires it, and it's a main component of any good roll bar. It can be removable by adding some double shear brackets.

Do you mean: from the point above my head where the rear brace meets the main hoop to where the passenger side brace meets the trunk floor? I have thought about it.

[David Pozzi]

Originally Posted by jlwdvm

Do you mean: from the point above my head where the rear brace meets the main hoop to where the passenger side brace meets the trunk floor? I have thought about it.

From driver's side main hoop just behind the driver's head, to the passenger floor where the main hoop is welded or bolted to the floor. It keeps the main hoop from deforming to the side and is usually required for any track use. It makes it hard to get into the back seat area, but can be made a bolt-in to make it easier to work back there doing upholstery or whatever.
A diagonal on the rear supports will help in torsion but not do much for safety.