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narrowing rear frame rails

38K views 36 replies 12 participants last post by  Blitz 
#1 ·
hey Ive been searching around and I doubt theres a how to on the subject but was wondering if anyone had a photo diary of narrowing the rear frame rails on their car. Ive seen maybe three pictures of it done after the fact but nothing about it in progress. More or less Im wondering how to keep everything squared up after everything gets cut and put back together. Im aware the best way would be to use a frame jig but short of having that is there any other effective ways of doing it and having satisfactory results afterwards? I know of one method for doing an aftermarket rear clip where you just build it inside the stock frame rails and cut the stock metal off after your done but Im figuring the method employed on cars like Mali2ude require a different process. If you have any pointers on doing this lemme know cause I hope to start on this project fairly soon (within the next week if possible) Thanks again hope you can help.
 
#5 · (Edited)
No I was planning on doing like what Demonic Obsidian or Mali2ude have done. The rear frame rails are cut off, narrowed, then gusseted on either side



I thought about notching it but I wanna give myself enough room for a 335 if I want it. I just cant think of a good way to keep the frame squared up once the whole back of the frame is lopped off.
 
#6 ·
I was thinking a 335 would fit if you notched the frame about 5/8 of an inch. My 315's fit very easy and a 335 is only an inch wider? thats a 1/2 per side, with a 12 inch wide rim and 7" offset. My 315 was on an 11" rim with 6 inch offset on a 67 rearend, 1/2 narrower than a 70 rearend. I'm going back with a 12 bolt rear from a 70, so a 7" offset and a 5/8 notch should work.
 
#7 ·
Hi Jody might chime in on this thread. He is the owner of the malitude now he may now a thing or two of what markstielow did. For me I did everything from the magazine article but did get it done I am currently cleaning up my weld which after the fact they look like crap.

for the actual frame narrowing from driver side to passenger side tac in some angle iron at these points first point in front of the lower rear just before the body mount then after the rear end after that body mount right around where your fuel tank would sit. Then after those are welded in tac from the forward angle iron to the crossmember in two points and the same in the rear to the crossmember at two points then make your cuts
 
#9 ·
First thanks for the input, second do you happen to know what issue the article about Malitude is where they actually do the frame? I look through super chevy and popular hot rodding and I dont thinkk they have that one article online.

Third If Im following you correctly you want to weld in braces between the rear body mounts in front of the gas tank and also between the body monts that are under the rear seat. Then weld in braces front to back from the forward crossbrace to the upper control arm crossmember and from that crossmember to the back crossbrace? Thats the way I understood your post but I may be totally off base.

Im probably just over complicating the whole thing but being that this is major structural surgery I want to know the right way to pull this off without trashing the frame.
 
#12 · (Edited)
thats just how I pictured it in my head. Ok from there Im figuriing that you make sure the frame is well supported all over the place in the back with jackstands. Then you take out even amount of material from both side of the upper control arm crossmember. Then you do your cuts fromnt and back and at that point youll have two frame rails that are loose and the center section of the UCA xmember is floating in midair by the braces. Then you just line up the UCA xmember pices and tack those then cut wedges of box steel to gusset the frame itself and weld those in and you got it licked. If I have the general gist of it right lemme know cause Ill start at it tomorrow night. Thanks again is almost time to start cutting!!
 
#13 ·
First of all make sure your frame is absolutly level front to back and side to side then tac weld your angle iron in place then do one frame rail at a time take it out modifie it then weld it back in place then do the opposite time. I can give you some pics if you run into trouble with the center crossmember
 
#14 ·
feel free to post them up anytime you like!! The more info the better but from the sounds of it I think I got the general idea or at least I think I do so now I gotta grap the plasma axe and actually do it lol
 
#17 ·
Ill have to track down a digital camera (my ex-better half got the one I had) but yes this is something Id like to document and give guys a better idea of how to do this. Granted Im not a high end chassis fabricator so Im sure itll have a few mistakes but I would definitely like to help out the community by letting guys see it from start to finish. Not to mention its nice to have a build diary to show off as well.
 
#19 ·
since you did it do you have any pointers on squaring the rails up after you cut them? I understand the bracing part and doing the gussets but what did you do to make sure everything lined back up except narrower? Ive been looking at the UCA crossmember and its isnt straight, it angles up a bit so my hope of just cutting out a few inces and sliding it back together lining it back up isnt going to happen. Its that part Im trying to make a game plan about. The body itself will be easy all I gotta do is write a check for it lol. (I hate body work with a passion so someone else can mess around with that)
 
#21 ·
ok so other than bracing up the center like was pictured before, just make the cuts scoot em in and just line up the top of the frame rails? No other jigs or bracing to hold the loose frame rail sections in alignment while they are being positioned in their new locations? Thats the part of this that has kept me from jumping into it and that is if there are any procedures for acurately setting the loose frame rails to the new spot without it being cockeyed.
 
#22 ·
measurements and more measurements......... take your time

id tack one in place then do the other. finish weld when its all done and you know its perfect. while your moving the frame rails, why dont you go with a 3 link and watts? its only a little more work :D
 
#24 ·
measurements and more measurements......... take your time

id tack one in place then do the other. finish weld when its all done and you know its perfect. while your moving the frame rails, why dont you go with a 3 link and watts? its only a little more work :D
Actually...... that was the plan from the start lol. I was originally going to just use an aftermarket rear clip but I figured the stock rails would fit better and require less cutting and subsequently less fabrication to rebuild the interior sheetmetal.

I saw a picture you posted and assuming its your car was wondering if the watts link you have is from Lateral Dynamics. It looks almost dead nuts to theirs, was just curious.

Frank at Prodigy was also kind enough to email me a bunch of pictures from when they narrowed the frame for the GTO they built. Now I have a pretty solid game plan of how to proceed, now all I gotta do is get some metal and start cutting!!! Im nervous and excited, Ive been planning this out in my head for months now and I think I have everything figured out
 
#25 ·
Matty B said:
I saw a picture you posted and assuming its your car was wondering if the watts link you have is from Lateral Dynamics. It looks almost dead nuts to theirs, was just curious.
its one i built, but i got the cradle idea from them. all the parts are from ballistic fab and jim fay at fays2. i drew all the brackets up on a cad program and had them water jetted. its now a parallel 4 link, with the front cross replaced and a chassis mounted splined sway bar.

Tim
 
#27 ·
Im in the process of building my crossmember at the moment. Ive had to cut in a drive shaft loop and also exhaust cutouts and get it cut to width with the right angle to match the frame where Im installing it. Ive been doing it as I have time although Ivebeen helping the shop owner next door to mine get his 68 camaro set up PT style so Ive had my time involved in his car. Hes more of a bolt on guy than me so we did the G-mod and springs,shocks, 600 steering box and new steering gear, brakes, subframe connectors and gears.... So far hehe. Im trying to get him to do a DSE deep tub kit, spring relocation and a T56.

As far as my frame goes I just need to keep it squared up only a bit skinnier. Shock and spring mounts will be taken care of afterwards since Im doing a three link and as of a few days ago shockwaves. If you want an idea of how Im doing things look at Widowmakers setup, add airbags and instead of a 4 link put a 3 link in and everything else will be the same.

I also just bought a full set of Nitto NT05's. The back end is getting 315's and it will tuck once Im done. I think Im gonna make enough room on the back side to fit a 335 slick but for now Ill be happy with a complete rolling chassis lol
 
#31 ·
#32 ·
thinning the rails on a 65 (which by the sig Im guessing this is) you wont gain much of anything. The 64-65 A bodies dont have any rear tire clearance to begin with and you dont get much more by thinning it an inch or so. To fit a large tire in my car it was determined that I needed to narrow the frame 7 inches total.

with a max width from wheel well lip to wheel well lip of 69.75" and a new outer frame rail width of 40.5", I ended up with 14.625" of wheel room per side. With a higher kickup via my custom frame rails, I can lay the car out on the frame and still not touch the axle to the chassis :)

You can see my frame work on my slowly updated build thread http://www.chevelles.com/forums/showthread.php?t=268217 . The rear is getting a 3 link, watts link, splined sway bar and coilovers or airbags, I keep going back and forth on that.
 
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