Rear Frame Rail Notching How To!

Before I take the car out again, I'm going to have to notch the frame rails for some new 15W slicks. I thought this would be a neat thread to start. I'll post the progress as things move forward. I'll also be installing an anti-roll bar. If anyone has suggestions or their own install documentation, feel free to pitch in on this. The more ideas, the better and stronger we can make this important modification.

hey Donnie

FYI
I bought a kit from one of the guys here on the board, already pre cut, with gussets, I've got one side done, then moved to new house so am still not done.
was very nice set up.
also alot of info on "yellow bullet .com" under suspension, then grandmas car, they just did a frame notch on a G body, and redid it after realizing needed more room, interesting reading! hope that helps!

Post some links.
Do you have any pics of your project?

Here you go gentleman. Frame Notch

Donnie,
Just a suggestion. Jack Cotton and his son Brian are experts at notching. No one has done it more than them. Give them a call for help. Also, I think their was a past issue of GMhightech mag that had an article with pictures about them notching a frame.

Check here:
1987 Buick Grand National Photo

Thanks for the links. Looks easy enough. I'll be installing an anti-roll bar at the same time. All I need is a plasma cutter. I have no mig, but I do have a tig. The welding will take longer, but it will look pretty.

One thing I'll be changing is how the ends are capped. I'm not fond of the small right angle plates. I'm sure it works well. Just not pleasing to the eye. I'm thinking of using a 45 degree angle plate instead of a 90 there.

I'm also thinking of including some internal bracing in the new thinner rail. Has there been any reports of excessive twisting of the thinner frames rails after a mod like this?

I like the 3/16" thickness. 1/4" sounds like too much. What do you guys think?

I'll take a wild guess that Dusty has a frame notch done to his car...and he runs in the 7's. If the notch is done correctly, and with proper bracing, you should be good to go. For added strength, I'd go with the 1/4"...but...that's just me.

Thanks for the input.

Let's start drawing up some ideas for bracing. Internal and external. Where are the load points? What sort of twisting forces are we going to be dealing with?

One of the members on the board here was selling a kit with braces. I'll do a search and try and find it. It would be nice if we could get members to post pics of this mod, including any bracing they've done.

I agree. Lee?

Yes, I believe his name is Lee...not sure if he is still producing these kits. Here's the thread. http://www.turbobuick.com/forums/parts-sale/251904-rear-frame-notch-kit.html

I mean Lee (cruzn57). He has one of those kits. Maybe he will share some pics.

I also like to add 2 internal "ribs". I use a small profile guage to make a nice fit, then cut it out and weld it it. I mark the location on the outside of te frame rail so I can hold the new frame section up to it and mark where the ribs are. Then I cut slots the thickness of the ribs in the new plate and weld the plate to the ribs. Then I grind it flat. I believe it adds lots of strength.

Very nice. I was thinking of the same with the slot idea.

I'm thinking of a little more bracing though. Creating triangulated pockets throughout the new section. That will make for a lot of slotting.

What is responsible for the body skin buckling of the rear quarter panel that I've seen posted?

I was just thinking. A mig would probably put less heat into the frame section. Less chance of warping the rail.

Good idea, but no need to go crazy I don't think. In that short section a few braces will keep the frame from twisting I would think.

Buckling on the launch seems to be caused from the frame twisting causing the right rear frame horn coming up and therefore left being pushed down.

Quite the contrary, TIG has a much smaller heat affected zone (if you are doing it correctly) than mig. Either way, that is why you jump around. Too tedious for me with TIG so I MIG it with the machine set kinda hot and weld an inch at a time. Be sure to brace the frame at the rear before you cut it out.

darn it, gotta work sometimes!

I have some pics at home, I can send you, or post,
the kit I got has inner braces /plate also, one at the top of the frame,(inside) another inside at front of the frame, near where lower arm connects, also included is a cross bar that goes between the frame rails.
To help eliminate body buckling, I planned to run a bar from roll bar ro rear bumper /frame area, to trianglate the frame, eliminate flex, and possibly an X to help lateral movement.
To gain maximum area, you will need to cut the frame to almost nothing,
leaving just the inner frame rail, thats why the kit has 1/4 in plate.
org frame looks like 1/8, so by using two, 1/4 plates , you will have sufficient material to help eliminate flex.
Donnie, when you plan to attack this? I'm off the 9th thru the 15th, (other than 12th) I can drive down and give you a hand.
tools I used were plasma cutter, die grinder with cut off wheels, saws all, and a torch, and of course a mig welder.
keep in mind, you will need to modify the wheel well, to optimize the frame notch, I chose to mini tub it.
let me know!

Wonder how hard the car launched to cause this. http://www.turbobuick.com/forums/parts-sale/233643-ottos-car-chopping-block-almost.html

So the body buckled after the frame notch. Sounds like there's a deficiency some where caused by the frame notching. Looks like he had a round tubing welded in between the frame rails also.

After alot of talking with the old-timer on this board this is what i decided to use. I went 3/16" hot rolled because 1/4" hot rolled is pretty weak in the grand scheme of things, and anyone who reuses their outer rails is simple a cheap.

DonWG, your are smart enough, but just remember, do not weld alot in one area. and make sure you brace the hell out of the rear frame rails before cutting anything, even if the braces are temporary. IT WILL WARP ON YOU IF YOU DO NOT USE BRACES!!!