I have heard of how unibody frames greatly benefit from being injected with expanding foam to increase rigidity, what I would like to know is if anyone has had success, or knows about, using industrial expanding foam inside the frame rails of a non unibody car. I have a 69 Bonneville I am getting ready to start and I am wondering if injecting the frame with foam would help in handling since the frame is so long. Thoughts...
I would think that it would be heavy and draw moisture. I have never done this so I can't say for sure.
It sounds like a great way to create rust spots in the frame. I worked on a lot of 69 Bonnevilles in the early 70's when I was the front end man at Frank Weaver Pontiac in Waco and trust me, those things have a hell of a strong frame and don't need foam to help them.
I have never heard about it making a frame more rigid.... But I will say it is used on many new cars to quiet things down. I think the new Ford F150 has it done from the factory. I would shoot paint inside the rail first I think. Spray foam makes a great hole filler in a tree to keep bees, and other rodent from hollowing it out, and does not hold water if painted over.
Most builders that I know of use steel in key areas to reinforce a uni-body frame. I really can not see how expanding foam can contribute to rigidity.
Yep, I agree that it would be a magnet for moisture and rust. Those frames did not need reinforcement unless damaged by rust outs, so just leave it alone. If you want to shoot anything inside it use cold galvanizing compound or some other rust inhibiting spray. Don
Some foam is in the 0.5pcf range so not very heavy. Also, there is both open cell and closed cell varieties; the closed cell does not/cannot hold moisture. As to the OP's question, I wouldn't bother. .
I can't see expanding foam having any use in a hot rod. I would stick to tried and true methods of using steel to increase rigidity. What are your plans for the car? Perhaps the forum can give you a better answer if your intentions for the car are laid out.
Yeah, it won't add and strength, it's just to keep down vibrations... I've done it to several dirtbikes over the years and it will dampen the vibrations some, but doesn't add one bit of strength...
I've done it many times on a unibody and it works very well to stiffen the chassis. I used the two part 4 or 8lb/cf urethane structural foal. You can do this but in a frame rail but I doubt it would make much difference because the frame is narrow and the steel is thick. You would also have to seal up the rail no water gets in and clean it very well so the foam could stick. Structural foam work best in large open voids like those found in a unibody which are usually sealed and therefore clean.
I've used expanding foam in crash structures in some OT road race cars, used it for energy dissapation in the event of a crash, not for increasing strength. Doesn't make sense to me.
I was going to say the same thing apart from working on them in Waco. I did get in a fist fight in Waco once, them guys are a little sensative about how you pronounce the name of thier town. Well that and tough as nails besides. There is jus something about hitting a guy as hard as you can and he just shakes his head and hits you back. Way easier to appologize and ask the right way to say it in that town for damned sure. Anyway if you want to help the bonney leave the frame along and update the suspension. Better springs, bigger brakes. late model corvette stuff is good and there are several aftermarket companies that make better springs for them. As for the unibody cars, foam bad idea, sub-frame connectors good idea and an easy alteration.
In the beginning days of ProStock they would acid dip the bodys to remove weight and spray on 2 part foam to get the rigidity back
Waco is a strange little town... First off the foam has been shown to stiffen the frame of unibodies as well as dampen sound and transfer kinetic energy through the car to the suspension via lessening flex. Second, with the closed cell foam water and rust are not an issue, in fact just the opposite. If done properly the foam would seal the inside of the frame and prevent water from entering in the first place. I thought it would be a long shot having any effect on the long thick steel rails compared to the open crevices of a thinner steel unibody but wanted to get some thoughts from everyone. As far as intent with the car, it is a convertible, and I am just planning on making a nice driver out of it. No road coarses or drag strips in its future; just wanted to see if this would help with handling. Porknbeaner, I am looking at doing better springs and bigger brakes. I haven't looked into the corvette, can you elaborate some on that? Also, the sub frame connectors are a good idea, I will have to explore this some more. Thanks to all.
If it is a UNI-BODY I don't think it has a frame just short pieces of tube for the suspension. Either way I would think a bonnie frame would not need any help unless it is rusted pretty bad then replacement would be the fix.
Unfortunately, I've tried contacting several suspension companies for suspension kits. Seems no one makes anything for full size Pontiac. Hotckis makes a kit for full size Chevys and it worked amazing.
The frame is in good shape, getting ready to coat with Eastwoods chassis restoration kit and figured if the foam would add an advantage then there would be no better time to do it than now.
GassersGarage, I am limited to upgrading springs and shocks up front. Out back I plan on using a G80 differential from 94-96 caprice/impala ss to add posi traction. There is a company that makes brackets to fit disc brakes but that is pretty much it as far as suspension and braking upgrades that I can find.
YAA!! do it! keep us informed!! 69 bonneville?? try a rudder and a sail too!! Now that thar made me spit out my coffee. GUD UN
Just box in the rear control arms and install some good bushings. Find a rear sway bar off a old high way patrol car to put on the rear it will take out the some of the body roll and make it more comfortable to drive.
69 bonneville rag top = nice car. My very first car was a 68 Bonny rag top. Neither one is a Hamb car though. I'm more than reasonably certain that foam in the frame rails will do little to zero for strength. It may help with sound resonance of the tube structure some but I never noticed any problems that needed to be solved anyway. I also think that the foam will cause you way more trouble than its worth. Have it dipped clean and dip coated inside & out and it ought to last another 40 some years. If the frame is sound and you have good body mount bushings shimmed correctly I don't think you'll have any trouble.
By 1969 the GM cars were sharing frames and suspension, the parts to rebuild should be out there, they may say Chevy on the boxes but are likely the same parts. A Bonneville is body-on-frame and IIRC the side rails are open C-channel. They're not quite as tough as the 71-76 style but they're fairly close. If it's flexing, there's rot someplace or it's been in a wreck - guys run demo derbies with these cars and smash them until they look like vaguely car shaped wads of tinfoil, and if they're solid they'll keep going and going. The only weak point is at the cowl where they spread out, they'll bend up there, if you were concerned you could add some bracing at that point, but it's not likely to ever be an issue in a driver.
The foam in a heavy frame such as the Bonneville won't increase the stiffness worth a damn. Keep thinking though.
A little OT, but considering were talking about "foam"..... When I bought my RED, it came with a 28 ft box type trailer that had plywood paneling inside. The moisture condensation had caused the plywood to separate, so I took it all out. Then I had a company that does insulation for refridgerated trailers "insulate" it. Using a spray-in, 2 part foam, they sprayed the walls and ceiling. Made the walls/roof EXTREMELY solid, and kept the inside cool on hot days. I painted the inside, and with the texture of the foam, it looked like rock, so the trailer was called "the cave". It also sealed a few water leaks in the aluminum skin of the trailer. Butch/56sedandelivery.
Uuhhhmmmm. I don't think there is enough foam to make a 60 Bonne handle! There is a heck of a lot of things you can do to that car to make it handle before you even have to think of something like foam. Reinforce rear control arms and a-frames. Stiffer springs and roll bar ect. It would also help if you could lighten the car by about 2000 lbs.
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