Body/frame stiffening

Ok, the 66 Bonneville is about to head off to the blaster/body shop. Before it does, I want to stiffen things up.

A bit of background: this car has 8-lugs all around; 10.5" FF axle, 3/4 ton front brakes/spindles, getting a full air suspension, and a duramax diesel.

So, my concern is not lightweight ways to stiffen a chassis for racing, my concern is making a good, stiff, squeak-free car. I thought about welding in some 1" square tubing on the bulkhead between the seat and trunk. Any ideas on where to add some bracing or firm up some existing bulkheads?

I'm also going to box the frame. I'll have some room to add crossmembers to the frame. Not a ton of room, but what might stiffen up the frame? An X-brace? Some crossmembers?

Will you be putting in a rollbar? One thought to control torque twist in the rails - connect the main hoop and rear down tubes directly to the frame then gusset and cross-brace them.

Boxing the frame will help a lot. I like the X-Brace for tying the two rails together. For stiffening in 3D, it would be hard to beat a rollbar, but that's not ideal for a cruiser. Perhaps just do what you can to stiffen in that axis under the floor pan, and with tie bars.

X the bulkhead between the rearseat and the trunk. It will help the torsional stiffness.Also x'ing the frame rails will help a lot.

If a roll bar is intrusive - how about instead of just reinforcing the existing bulkheads on the body - make some 3D bracing that lays up against it just ahead of the firewall and just behind the rear seat. There should be room to make a hoop between the engine and trans just in front of the tunnel - especially since the diesel can't use the vacuum brake booster. Anything that can give you a vertical plane to keep the twist in check.

Yeah, no rollbar. This is a luxo-cruiser hardtop.

There should be room to make a hoop between the engine and trans just in front of the tunnel

There should also be room to add more bracing to the radiator core support, then I could tie that hoop to the one you suggest along with tying into the upper shock mount/control arm mount.

I'm basically making my 66 Bonneville into a truck :)

In reply to curtis73:

I was just thinking that starting with a rolled 2500HD and dropping the Bonneville on it might be easier.

Thought of that... not even close. Unless I want it to look like a truck

Have you seen the rear suspension kit for 1965-1970 B body Pontiacs from Ramair Restorations? It will help quite a bit in the handling department, there's some frame stiffening brackets included: http://www.ramairrestoration.com/catalog/product_info.php?cPath=31_30&products_id=371

Also, Roush has come out with a nifty front disk brake conversion kit for 8 lug wheels: http://forums.performanceyears.com/forums/showpost.php?p=4182805&postcount=26 A friend of mine is installing a set on his '61 Ventura; I haven't seen them yet in person but he says the kit is very nice.

Structural Foam GRMhow about structural expanding foam in all the body openings that are unseen?

GRM Structural Foam

stuart in mn wrote: Also, Roush has come out with a nifty front disk brake conversion kit for 8 lug wheels: http://forums.performanceyears.com/forums/showpost.php?p=4182805&postcount=26 A friend of mine is installing a set on his '61 Ventura; I haven't seen them yet in person but he says the kit is very nice.

Great idea, but wrong 8-lugs. This isn't the pontiac 8 lug, this is a truck 8 lug.

This is my setup:

stuart in mn wrote: Have you seen the rear suspension kit for 1965-1970 B body Pontiacs from Ramair Restorations? It will help quite a bit in the handling department, there's some frame stiffening brackets included: http://www.ramairrestoration.com/catalog/product_info.php?cPath=31_30&products_id=371

Also a great idea... but when I put the 14-bolt rear in I had to do custom trailing arms on the lowers to bring them inboard about 2". But I might copy their idea with my own welder

mad_machine wrote: Structural Foam GRMhow about structural expanding foam in all the body openings that are unseen? GRM Structural Foam

Ooooh... I like. There are TONS of unused cavities in this car. I can fill a lot of spaces.