Welding Unibody Seams?

RIGGATONY66 · 01-02-2012, 09:36 PM

Happy New Years everyone. I have been reading the forum for sometime now and found it very helpful, Thanks. I have a 66 Chevy II Sport Coupe that I'm building for bracket racing. I plan on installing sub frame connectors and a 6pt roll bar. Will welding the uni-body seams help strengthen the body and keep the car from flexing? Would this be a waist of time? The car has a small block, 4 speed and 4:88 gears using M/T ET STREETS. Thanks for the help.

Geerhead55 · 01-02-2012, 10:39 PM

Welcome to the forum,,,theres a bunch of Chevy II guys on here that will jump in I'm sure. I had a '66 Nova SS in the '70s, a stick car, and one problem I remember we had was with firewall flexing. You could stand there and watch while a buddy pushed the clutch in and see the master cylinder move back and forth with the pedal movement. I'm not sure what they do nowadays but back then we made a brace from the shock tower to the mastercylinder mount. I had a 6 point roll bar also which really stiffened things up, but I know I should've had frame connectors. We didn't bother with welding the body seams. Good luck with your car,,,keep us updated with your progress, especially with pictures.
Danny Durham

Myron Piatek · 01-02-2012, 11:30 PM

Make it an 8 point with short bars behind the seats going from the sides of the main hoop at the cross-bar down into the frame connectors. Triangulation is the key. Welding the uni-body seams can only help if you want to go through the trouble.

Tom Goldman · 01-02-2012, 11:30 PM

Spend the time you would spend on welding the seams, not recomended, and use it to put in a complete roll cage rather than a roll bar.
A 4 speed car will thank you for the extra stiffness the cage will provide.
I would add a bar from the cage to the firewall to stiffen the front clip mount area.
You can also add a brace from the cage bars to the area Danny mentioned to stiffen the clutch/brake mounting.

Myron Piatek · 01-02-2012, 11:35 PM

Quote:

Originally Posted by Tom Goldman

Spend the time you would spend on welding the seams, not recomended, and use it to put in a complete roll cage rather than a roll bar.
A 4 speed car will thank you for the extra stiffness the cage will provide.
I would add a bar from the cage to the firewall to stiffen the front clip mount area.
You can also add a brace from the cage bars to the area Danny mentioned to stiffen the clutch/brake mounting.

Tom, I understand a full cage will help, but why would welding the seams not be recommended? It's an awful lot of work, of course, but I can't see how it would hurt.

RIGGATONY66 · 01-03-2012, 12:17 AM

Thanks for the replies, I'm making notes. Never know about the firewall flex. That's information that is great to hear about. I can plan some welding to support up that area. I'll get some pictures up shortly.

Mark Ugrich · 01-03-2012, 12:51 AM

With clutch pressures in the 200-300lb range I doubt firewall flex will be a problem.On my own car, once I put an updated clutch in it, the overcenter spring would hold the clutch pedal to the floor.

I agree adding a full cage would be time well spent.Good luck with your project.

Tom Goldman · 01-03-2012, 09:18 AM

Quote:

Originally Posted by Myron Piatek

Tom, I understand a full cage will help, but why would welding the seams not be recommended? It's an awful lot of work, of course, but I can't see how it would hurt.

The problem with welding seams ,especially on an old body with possible rust and remanants of seam sealer, is undercutting the sheetmetal next to the seam and actually weakening the structure rather than making it stronger.
If the body has been chemical stripped or blasted, tig welding the seams with silicon bronze is a good way to do it ,but not mig welding.
The best thing is to make the cage an integral part of the body structure so it does the work ,not the body.

Dwight Southerland · 01-03-2012, 10:25 AM

Tom -
I appreciate your in-depth knowledge and analysis concerning this topic. While your rationale is inviting and attractive, real world experience will prove that welding the seams in a unibody car will make the car more rigid and reduce flex. You can increase strength significantly with a well -designed cage so that the unibody factor is reduced, but under current Stock Eliminator restrictions for cage construction, the stitched up seams will be a benefit. I agree with your comment about tig welding as a preferred method.

01-02-2012, 09:36 PM	#1
RIGGATONY66 Junior Member Join Date: May 2009 Location: Pilesgrove NJ Posts: 4 Likes: 1 Liked 1 Time in 1 Post	Welding Unibody Seams? Happy New Years everyone. I have been reading the forum for sometime now and found it very helpful, Thanks. I have a 66 Chevy II Sport Coupe that I'm building for bracket racing. I plan on installing sub frame connectors and a 6pt roll bar. Will welding the uni-body seams help strengthen the body and keep the car from flexing? Would this be a waist of time? The car has a small block, 4 speed and 4:88 gears using M/T ET STREETS. Thanks for the help.

01-02-2012, 10:39 PM	#2
Geerhead55 VIP Member Join Date: Sep 2002 Location: Tacoma, Washington Posts: 1,632 Likes: 0 Liked 5 Times in 5 Posts	Re: Welding Unibody Seams? Welcome to the forum,,,theres a bunch of Chevy II guys on here that will jump in I'm sure. I had a '66 Nova SS in the '70s, a stick car, and one problem I remember we had was with firewall flexing. You could stand there and watch while a buddy pushed the clutch in and see the master cylinder move back and forth with the pedal movement. I'm not sure what they do nowadays but back then we made a brace from the shock tower to the mastercylinder mount. I had a 6 point roll bar also which really stiffened things up, but I know I should've had frame connectors. We didn't bother with welding the body seams. Good luck with your car,,,keep us updated with your progress, especially with pictures. Danny Durham

01-02-2012, 11:30 PM	#3
Myron Piatek VIP Member Join Date: Nov 2001 Location: Florida Posts: 1,542 Likes: 34 Liked 138 Times in 51 Posts	Re: Welding Unibody Seams? Make it an 8 point with short bars behind the seats going from the sides of the main hoop at the cross-bar down into the frame connectors. Triangulation is the key. Welding the uni-body seams can only help if you want to go through the trouble.

01-02-2012, 11:30 PM	#4
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,473 Likes: 881 Liked 858 Times in 234 Posts	Re: Welding Unibody Seams? Spend the time you would spend on welding the seams, not recomended, and use it to put in a complete roll cage rather than a roll bar. A 4 speed car will thank you for the extra stiffness the cage will provide. I would add a bar from the cage to the firewall to stiffen the front clip mount area. You can also add a brace from the cage bars to the area Danny mentioned to stiffen the clutch/brake mounting. __________________ Tom Goldman 1500 SG , 1506 STK

01-03-2012, 12:17 AM	#6
RIGGATONY66 Junior Member Join Date: May 2009 Location: Pilesgrove NJ Posts: 4 Likes: 1 Liked 1 Time in 1 Post	Re: Welding Unibody Seams? Thanks for the replies, I'm making notes. Never know about the firewall flex. That's information that is great to hear about. I can plan some welding to support up that area. I'll get some pictures up shortly.

01-03-2012, 12:51 AM	#7
Mark Ugrich Member Join Date: May 2011 Location: Auburndale,Florida Posts: 220 Likes: 29 Liked 71 Times in 38 Posts	Re: Welding Unibody Seams? With clutch pressures in the 200-300lb range I doubt firewall flex will be a problem.On my own car, once I put an updated clutch in it, the overcenter spring would hold the clutch pedal to the floor. I agree adding a full cage would be time well spent.Good luck with your project.

01-03-2012, 10:25 AM	#9
Dwight Southerland VIP Member Join Date: Dec 2001 Location: Arkansas - In the middle of everything. Posts: 1,999 Likes: 63 Liked 772 Times in 192 Posts	Re: Welding Unibody Seams? Tom - I appreciate your in-depth knowledge and analysis concerning this topic. While your rationale is inviting and attractive, real world experience will prove that welding the seams in a unibody car will make the car more rigid and reduce flex. You can increase strength significantly with a well -designed cage so that the unibody factor is reduced, but under current Stock Eliminator restrictions for cage construction, the stitched up seams will be a benefit. I agree with your comment about tig welding as a preferred method.