Rear Frame Rail Notching How To!

[DonWG]

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.

[cruzn57]

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!

[DonWG]

Originally Posted by cruzn57

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?

[SCOOBY DOO]

Here you go gentleman. Frame Notch

[chrisgarrett]

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.

[chrisgarrett]

Check here:
1987 Buick Grand National Photo

[DonWG]

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?

[SCOOBY DOO]

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.

[DonWG]

Originally Posted by SCOOBY DOO

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?

[SCOOBY DOO]

Originally Posted by DonWG

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.

[DonWG]

Originally Posted by SCOOBY DOO

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?

[SCOOBY DOO]

Originally Posted by DonWG

I agree. Lee?

Yes, I believe his name is Lee...not sure if he is still producing these kits. Here's the thread. Rear Frame Notch Kit

[DonWG]

Originally Posted by SCOOBY DOO

Yes, I believe his name is Lee...not sure if he is still producing these kits. Here's the thread. Rear Frame Notch Kit

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

[disco stu]

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.

[DonWG]

Originally Posted by disco stu

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.

[disco stu]

Originally Posted by DonWG

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.

[cruzn57]

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!

[SCOOBY DOO]

Originally Posted by DonWG

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?

Wonder how hard the car launched to cause this. Otto's car on the chopping block,Almost !!

[DonWG]

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.

[karolko]

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!!!

[Dusty Bradford]

The quarter panel wrinkle is common on cars with frame notches. I have seen several builders add a reinforcing tube to the rear of the frame between the frame and the coil spring. I think it will help but is not the answer.

When looking at how the suspension works. You have the upper arms pulling on the frame and the lower arms pushing on the frame. IMO the only way to properly brace the frame after notching is by tieing it into the roll cage. You will need to tie the roll cage into the suspension points. This will be the area on top of the coil spring. From the coil spring back the only function of the frame is to hold the bumper up. By tieing the roll cage into the coil spring cup you take the load off the frame in the coil spring and the upper control arm frame mount areas. The roll cage will help fight the powers that are pulling on the upper control arm mounts on your frame when the car launches.

[karolko]

Dusty i couldn't agree with you more. Well Put.

[DonWG]

So you're saying I should just back half the bitch now.

[six shooter]

That would be my choice since you don't have to worry about class rules. If you want to keep the stock suspension pick up points, I would bend tubing rails to follow inside the stock pieces and build off of that. If you need MIG or a plasma cutter let me know. I would be happy to let use whatever I have.

[DonWG]

Originally Posted by six shooter

That would be my choice since you don't have to worry about class rules. If you want to keep the stock suspension pick up points, I would bend tubing rails to follow inside the stock pieces and build off of that. If you need MIG or a plasma cutter let me know. I would be happy to let use whatever I have.

Thanks six shooter. I'm going to be looking into this carefully before I start cutting things up. I know... bracing first.

[steve hughes]

When i notched mine i added a rear driveshaft loop between the lower control arm mounts and ran two tubes up from the loop to the upper control arm box. Ther are some pics in my photo bucket site in my signature. I broke a rod end on the anti rollbar last year on the launch. Left front wheel was about 5 feet off the ground and the about one foot. No quarter panel buckle or b post crack after that and many many hi 1.2 to low 1.3 60 foot times. Simple approach but it seems to work.

[Quick Turbo V6]

Here is how mine is done for now.

HTH,
Scott

[Dusty Bradford]

Originally Posted by DonWG

So you're saying I should just back half the bitch now.

Not at all. I knew where some pics we're that showed alot of the cage work that I'm talking about. They aren't where they used to be so I have e-mailed the guy to find out where they are. The roll cage main hoop needs to be tied into the suspension points. The rear down bars should go to the top of the spring mounts. I will be away from the computer all day working on a car but I'll dig up some pics in the next few days to help explain what you need to look into.

[DonWG]

Originally Posted by cruzn57

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!

Finally checked out Scooby Doo's link to your install. Very interesting. I'm getting some ideas.
The frame actually does a lot of work in the area of the spring perches up forward to the lower control arm mountings. The overlapping stock channel offers a lot of strength compared to a flattened member, no matter how thick. I see some boxing, channeling and bracing will be needed.

[Dusty Bradford]

Here's a few more pics of some bracing.

http://www.outlawradial.net/suspensionpics.htm

[Fat Tony]

Originally Posted by DonWG

So you're saying I should just back half the bitch now.

You might as well, less work better chassis.

[twin 93 svt]

nice pic's

[DonWG]

Originally Posted by twin 93 svt

nice pic's

+1. Thanks for the link Dusty. Good food for thought.

[Louie L.]

Don,
Something to think about. Make your notch big enough for a tire upgrade in the future. Ive seen many notch jobs that with fit a 28x10 MT and thats it, me included. We deal with the depth issue but not the leght. I just upgraded to a 295/65 MT drag radial 30 in dia. The tire was hitting the front and rear most section of the tire.

So i had to go in there and modify a 5 year old notch job and it sucked LOL

[Dusty Bradford]

Originally Posted by Louie L.

Don,
Something to think about. Make your notch big enough for a tire upgrade in the future. Ive seen many notch jobs that with fit a 28x10 MT and thats it, me included. We deal with the depth issue but not the leght. I just upgraded to a 295/65 MT drag radial 30 in dia. The tire was hitting the front and rear most section of the tire.

So i had to go in there and modify a 5 year old notch job and it sucked LOL

I dread going back into mine. I'm good for a 30" tire but I want the 315/60 to fit inside. That will be ALOT of work.