Cutting frame in half and welding in a new section

[truracer20]

You have to find and record reference points for every axis. No floor surface will be flat or level, you have to build supports to be level and they have to remain in the same place the entire time. Ideally this should be done under the original frame so that once the rear section has been removed the new one can rest on those supports. If you have to weld some braces in before removing the body because the rail is rusted in two, then do so.
And if it were me I would try to get the two to fit so that the ends of the inner and outer rails are staggered and the top and bottom of the inner and outer rails overlap like the factory did it, then butt weld the vertical ends. After the butt welds were done I would plate over them for added rigidity. I would find good reference points on both sides to cut the front section to the same length on both sides, then trim the rear section a little at a time to get an exact fit. It can be done but take your time and double check measurements as you go. Also take your time with the welding, use plenty of tack welds and use small stitch welds working from side to side so you don't warp the frame.

 

[-83MONTESS-]

May I ask what the reason for ruling out a full frame swap is? It's less work and no worry about the strength of the welds or dimensions. Either way the body is coming off. Why not find a frame, assemble the suspensions, and drop the body on it? Then swap in drivetrain and be done with it. Seems silly to me to create more work...

 

[81msw79]

I would have to agree with Monte83ss. it makes no real sense to go thourgh all the work to hack and chop a frame unless you are doing a back half for a prostreet application. all the un need work ,time and aggravation would be better spent buying a clean frame and boxing and bracing that before dropping on the body.

 

[bigbub37]

i hear back and forth people saying they have done it and others saying to never attempt it. I just want to know if anyone here has done it. odds are im gonna attempt it so just wanna hear from people. my frame is solid from the front all the way back to the door jams, luckily enough I found a half a frame that goes from the door jams back and its spotless. when I weld it together im gonna do a lot of bracing on it and notch it and run cross braces between the rear frame rail. I just wanna know if anyone has done such a thing on here.

I replaced the back half of my from back in 2010. as u know the back half is welded to the frame rails.if u cut the welds the back frame is shaped to fit over the rails like a puzzle. the best way to in stall if u dont have a jig is to sit the frame up in the car and get it lined up. like I said the back frame will slide over the rails and install all the bushings and bolt it in and make sure u have the frame good and straight and that it doesnt sag in the middle and when u think u got it in place and where u want it then u can weld it in. thats how I did mine rolls perfect and theres no dog tracking.

 

[pontiacgp]

even if you have it set up to be straight and then weld without have the frame secured to a jig the welding can twist the metal. Even boxing the C section will cause the c section to bow out enough to cause you problems getting the frame under the car.