Installing front sub frame rail
- Thread starter Cythomas
- Start date
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Professor Fate
Push the button, Max...
Is your existing frame rail solid? Not rusted? If so, I wouldn't be too quick to start cutting and replacing until you have a frame shop take a look at it- they should be able to pull that back to spec without too much trouble, hard to say for sure from the pic but definitely worth checking with them. And it will all be square... unless you have some frame rot, then you're back to replacement. The frame shop will have the factory specs, which are also in the factory body & frame manual.
moparmat2000
Well-Known Member
If you really want to do this, you need to be smart about it. Take lots of measurements for starters. I would recommend removing the engine, and transmission, front suspension and use a bare empty K frame as part of your jig.
Now for a possible part of the problem. K frames are jig weld assembled in a fixture and ALL of them are exact at all 4 points so any 67-76 A body K frame will swap to any 67-76 A body. These are held on with shouldered bolts that locate it EXACT on 4 points. If your K frame is bent from the fender bender I would NOT use it to line up your new framerail. Your better off using a known straight K frame for that. The 2 shouldered K frame bolts, Theres your 2 points to get the rail square.
First thing you want to do go buy 4 cheap magnetic spirit levels. I got mine from Northern Tool for about $2 each. Remove your trunk mat, and door sill plates on both doors. Get the car jacked and level on 4 points. Your concrete floor is not dead level, so you have to make sure the car is. Put one spirit level on each rocker in each door opening facing front to back, one in the trunk across the the transition pan above where the the shock bolts are facing side to side, and one across the upper radiator support on the lip by the radiator top tank facing side to side.
If your replacing the inner fender along with the framerail either temp weld or make and install temporary bolt on supports from the firewall to the radiator support before any removal to keep everything lined up. I recommend removing the inner fender from the replacement rail, then install the replacement rail, then install the inner fender second. It will be difficult to line it up as a complete assembly. Car in the pix has jack stands under the rear axle that are shimmed to make the bubble level in the back level from side to side. Jack stands in the front are on the torsion bar crossmember, and shimmed with thin aluminum shims to make the door opening sills on the rockers level and radiator support level.
The inner fender also has 5/16" diameter alignment holes at top front and top rear to line it up at the back and front. Use 5/16" diameter flat bottom punches to line them up before clamping and welding. Check every measurement multiple times before buzzing it together.
Remember that the whole car is nothing but alignment holes. Last pic if looking straight down through the holes that have body plugs in them in the trunk floor and transition pan. There are corresponding holes lined up at the bottom of every LH and RH framerail in these same spots. This is where the framerails were set down into an assembly line jig with multiple steel pins sticking up. The floor pan sheetmetal was then set down onto the same pins over top of the framerails and clamped together. Then workers proceded to pinch it all together with spot welders at the factory. Remember they made 275,000 dodge darts in just 1969 this doesnt include the number of valiants and barracudas in this same year. This is a lot of effing cars. This stuff had to have ways to fit it together on the assembly line quickly and accurately especially in regards to suspension and K frame locating.
Hope this helps you out. Best of luck.
Now for a possible part of the problem. K frames are jig weld assembled in a fixture and ALL of them are exact at all 4 points so any 67-76 A body K frame will swap to any 67-76 A body. These are held on with shouldered bolts that locate it EXACT on 4 points. If your K frame is bent from the fender bender I would NOT use it to line up your new framerail. Your better off using a known straight K frame for that. The 2 shouldered K frame bolts, Theres your 2 points to get the rail square.
First thing you want to do go buy 4 cheap magnetic spirit levels. I got mine from Northern Tool for about $2 each. Remove your trunk mat, and door sill plates on both doors. Get the car jacked and level on 4 points. Your concrete floor is not dead level, so you have to make sure the car is. Put one spirit level on each rocker in each door opening facing front to back, one in the trunk across the the transition pan above where the the shock bolts are facing side to side, and one across the upper radiator support on the lip by the radiator top tank facing side to side.
If your replacing the inner fender along with the framerail either temp weld or make and install temporary bolt on supports from the firewall to the radiator support before any removal to keep everything lined up. I recommend removing the inner fender from the replacement rail, then install the replacement rail, then install the inner fender second. It will be difficult to line it up as a complete assembly. Car in the pix has jack stands under the rear axle that are shimmed to make the bubble level in the back level from side to side. Jack stands in the front are on the torsion bar crossmember, and shimmed with thin aluminum shims to make the door opening sills on the rockers level and radiator support level.
The inner fender also has 5/16" diameter alignment holes at top front and top rear to line it up at the back and front. Use 5/16" diameter flat bottom punches to line them up before clamping and welding. Check every measurement multiple times before buzzing it together.
Remember that the whole car is nothing but alignment holes. Last pic if looking straight down through the holes that have body plugs in them in the trunk floor and transition pan. There are corresponding holes lined up at the bottom of every LH and RH framerail in these same spots. This is where the framerails were set down into an assembly line jig with multiple steel pins sticking up. The floor pan sheetmetal was then set down onto the same pins over top of the framerails and clamped together. Then workers proceded to pinch it all together with spot welders at the factory. Remember they made 275,000 dodge darts in just 1969 this doesnt include the number of valiants and barracudas in this same year. This is a lot of effing cars. This stuff had to have ways to fit it together on the assembly line quickly and accurately especially in regards to suspension and K frame locating.
Hope this helps you out. Best of luck.
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Professor Fate
Push the button, Max...
The only caveat that I can add to this excellent info is that the OP's front end hit may not allow him to use a level across his radiator yoke- he may need to use a workaround such as leveling his body across the front framerails back towards the firewall, where damage/distortion is probably minimal and using that to locate the rear of the replacement rail; then squaring up the front of the rail to the opposite rail. He may have to do a bit of yoke/inner fender tweaking after that to get the sheetmetal back into it's proper place.
moparmat2000
Well-Known Member
Plus if the existing K frame is bent, you wont know it. It would suck to line up the replacement frame rail with a tweaked K frame, then you end up with a bastard that no other K frames will fit except for your bent one. I would use any 67-76 K frame either V8 or slant 6 that's known to be straight as a jig to install this framerail. Then if your original K doesnt line up after that, you will know yours is indeed bent. At that point go looking for a replacement K frame.
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Killer tutorial Matt, going save this post for when I replace mine.
Cythomas
Active Member
Thanks so much Matt ! Very though information, yes I have another k member out of an a body
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