Frame Notching again!

[BoostedBug]

Well i did a search and see where some have problems with a dent popping up in the rear 1/4 panel on a hard launch.

I want to run a big tire on the car as it is mostley just a street car to me but here is my question and my idea on how to help keep the dent from happening.

I know this has been beat to death but i want to run a 325 on the car and keep the tire under the body. I do not like the look of a tire sticking out or the car jacked all up. the lips have already been masaged on my car.

Would a 5" back space 15X10 be the best size for this? I see some use a 5.5 back space but have to run a spacer.

My idea on fixing the flex was that i would use an x brace style setup. Chrome Molly roll cage bar welded in like in the picture.. What do yall think?

[

 

[bruce]

Well i did a search and see where some have problems with a dent popping up in the rear 1/4 panel on a hard launch.

I want to run a big tire on the car as it is mostley just a street car to me but here is my question and my idea on how to help keep the dent from happening.

I know this has been beat to death but i want to run a 325 on the car and keep the tire under the body. I do not like the look of a tire sticking out or the car jacked all up. the lips have already been masaged on my car.

Would a 5" back space 15X10 be the best size for this? I see some use a 5.5 back space but have to run a spacer.

My idea on fixing the flex was that i would use an x brace style setup. Chrome Molly roll cage bar welded in like in the picture.. What do yall think?

[

Any bracing you do is going to be a good thing.

I have 17x9 with a 5" BS, and lots of room, with my 285/40s. I'm still undecided about rims, for some bigger tires, but it seems, 17x11s, with a 5.5 should still clear everything.

 

[SPEEDSTAR]

Thats how I am going to do mine, its a proven way to really help chassie strength,. Have you knotched yiur frame rails yet? I am just finishing mine. I am using 3/8 hot roll plate. I cut the rails and plate with a side grinder and 4 1/2 cut off disc so that the 3/8 pieces will fit flat against the inside of the rails by radiusing the inside edges, here are some important tips that really make a difference. There are a couple of places were the back inside of the rail protrudes out , cut it from the bottom up with a cut off wheel about half way up and hammer it back flat and weld it on the back later, also were you first cut in and out needs to be hand bent in or hammered in for more and straighter clearance. When you make you carboard templates , do them in 5 or 6 sections. You also need to chamfer the outside edges of each part for weld strength and while you have them clamped in , hammer the frame rail edges down for a tighter fit and easier welding. I also welded in a length of DOM 2" by .120 wall tubing between and inside the rails for added strength, . Next I will box in the frame rails where the need it. Jeff

 

[SPEEDSTAR]

I am using an 18 by 10 rim and a 305 tire, but I could have easily gone with an 11"wide rim. Jeff

 

[Louie L.]

I have noticed that the cars that usually exibit this dent have the original frame material used in the boxing procedure of the frame notching. As Speedstar suggested, boxing the frame with heavier gauge steel provides extra strenght over using the stock thin, weak steel. This is just my observation.

I used flat steel sheet stock of 1/8 in to box my frame. So far no dents with mid 1.3 60 fts...

 

[GNVYUS 1]

Louie is right on as usual.

My body guy who did my awesome metal fender flare extensions said the same thing. When they do notches, they use heavier gauge metal for the frame to made it stronger in that area. It adds labor time but its well worth it in the long run.

 

[V6RACER]

I have noticed that the cars that usually exibit this dent have the original frame material used in the boxing procedure of the frame notching. As Speedstar suggested, boxing the frame with heavier gauge steel provides extra strenght over using the stock thin, weak steel. This is just my observation.

I used flat steel sheet stock of 1/8 in to box my frame. So far no dents with mid 1.3 60 fts...

I used 1/8" plate on mine and I have the crease. I think it comes from strapping the car down on the trailer attaching the straps to the rear section of the frame and then then pulling it down too tight. Just a thought. If you hook onto the rear axle to strap it down you don't put as much stress on the weak rear section of the frame.

 

[Dusty Bradford]

I used 1/8 plate on mine also. I cut the rail back to the rear part of the frame leaving only about 1/8 or so of the original rail for my plate to fit inside for welding.

After watching several cars at the nats creasing the quarter panels I was determined for mine not to do it. I noticed they all did it on launch and the dent then popped back out. The bad thing is the metal is now weak and warped so it's really noticeable. My opinion was that as the car is leaving the rear end is pushing upwards on the springs and the upper control arms are pulling on the frame. That's why the body creases inward, the frame behind the rear end is flexing upward. This area is where we have to notch the frame. What I've done is have a nice roll cage tied into the frame. We ran the rear bars of the cage directly on top of the spring mount perch on the frame so that the cage will hopefully prevent the frame flexing upward. Then under the bottom we ran a 1 inch tube from the upper control arm mount points to the lower control arm mounting points. The thinking behind this was that as the uppers are pulling on the frame, the lowers are pushing on the frame and these bars will tie them together to maybe counter act each other. I also used the HRparts brace kit on the lower mounts.

Strapping it down by the frame could be a problem to but I've always strapped mine with the rear housing.

 

[TURBOV6]

A 325 size tire is too wide a 315 is the max you can go with. On a 15 x 10 with a notched frame the back spacing would be a 5.5".

The welder who notched my frame us 1/4" steel on my car instead of 1/4". If you are worried about weaking the frame/body go with a 6pt roll bar.

 

[bruce]

What I had done to mine, was splitting the frame rail, and then grinding down the welds, and stuffing the removed piece further into the existing frame rail.. While I didn't get as thin (or wide of) mintub, by maintaining a larger *box*, the frame rail is now stronger, in that area, then just sandwhiching a plate in there. Bending motions happen in all directions, as a launchs. Triangulating, and maitaining box sections, are all terrific design elements for stopping the frame/body from twisting.

Using the poly type frame to bosy bushings would help.

If the car's been doing this for a while, then as Dusty said, it's roll cage time.

http://home.woh.rr.com/brucesgn/minitubs/

 

[Louie L.]

I used 1/8" plate on mine and I have the crease. I think it comes from strapping the car down on the trailer attaching the straps to the rear section of the frame and then then pulling it down too tight. Just a thought. If you hook onto the rear axle to strap it down you don't put as much stress on the weak rear section of the frame.

Does yours do it now with the new sway bar ?

 

[Epitome]

Well...my car is notched and I haven't had any dent issues with a bunch of 1.4x 60 foots. I use a 325/50/15 BFG DR on the street on a 15x10" rim with a 5.5" backspace and nothing ever rubs. I am not sure whether the stock steel was used to complete the notch.

 

[GO FAST]

Just my opinion , if I could start over again I would not notch the frame its only going to weaken the chasis and make it easier to twist and flex , besides all you need is a 10.5 " tire anyway......... BTW that big ugly dent is on the driver side rear quarter as you see this picture.

 

[GO FAST]

Maybe you can see it in this picture....

 

[SPEEDSTAR]

In addition to what I said earlier on how I notched my frame rail, I clamped the 3/8 plate inside the frame rails and ground flush any of the original rail that stuck out past the 3/8 plate. I will weld the cage bars to the top of the upper spring mount, except Iam using coil-overs,then weld a tube between those two inside the trunk, then add two short tubes at an angle from the crosstube to the crosstube welded in at the rear of the frame notch under the trunk. Its only 5-8 lbs. more weight ,but I think it will be worth the extra strength. I am also looking at adding tubing to the front of the notch. I believe that a car with 800 to 1000 hp and notched frame would benefit from the extra strength over the added weight. I will also triangulate the bars that go from the top of the hoop to the shock top mounts ,and use poly body mounts..... Jeff

 

[BigBlockOlds]

Hmmm...this is the first I have heard of the 1/4 panel problems and I've already notched my frame rails. LOL I used the stock outer part of the frame and welded it back in place after notching so it would look more "factory" from the side.

We are going to brace the frame diagonally (hopefully if room allows) to parts of the frame just in front of and behind where we notched the frame. Although it sounds like I may have to add a 6 point roll cage for reassurance.

One question, these cars that are creasing the 1/4's, are they just mostly hard launching drag cars or street cars also? My '87 Olds I'm building will be more of an Autocross/street car. I'll be running a 500-550HP 425cid big block with a T56 6 speed and 17x11 wheels with 315-335 series tires. Definitely no slicks.

Here's a picture of the frame notch and one with the wheels/tires added:

http://home.woh.rr.com/designsofarch/index/olds_site/notch6.JPG

http://home.woh.rr.com/designsofarch/index/olds_site/Frame04.jpg

Thanks,

 

[GO FAST]

Hard launching drag car on the weekends , street car on the weekdays

 

[jimmag]

I used 1/8 plate on mine also. I cut the rail back to the rear part of the frame leaving only about 1/8 or so of the original rail for my plate to fit inside for welding.

After watching several cars at the nats creasing the quarter panels I was determined for mine not to do it. I noticed they all did it on launch and the dent then popped back out. The bad thing is the metal is now weak and warped so it's really noticeable. My opinion was that as the car is leaving the rear end is pushing upwards on the springs and the upper control arms are pulling on the frame. That's why the body creases inward, the frame behind the rear end is flexing upward. This area is where we have to notch the frame. What I've done is have a nice roll cage tied into the frame. We ran the rear bars of the cage directly on top of the spring mount perch on the frame so that the cage will hopefully prevent the frame flexing upward. Then under the bottom we ran a 1 inch tube from the upper control arm mount points to the lower control arm mounting points. The thinking behind this was that as the uppers are pulling on the frame, the lowers are pushing on the frame and these bars will tie them together to maybe counter act each other. I also used the HRparts brace kit on the lower mounts.

Strapping it down by the frame could be a problem to but I've always strapped mine with the rear housing.

 

[ttypewhite]

I am using an 18 by 10 rim and a 305 tire, but I could have easily gone with an 11"wide rim. Jeff

Do you have any pics you could share? My new setup will be using the same size rim and tire. I am very interested in how yours turns out.

 

[pacecarta]

holy old thread dug up from the past..

i notched my frame , used 3/16 plate , rolled the lips , kept inner wheelhouses with a little massage at the ends
15x 10 weld aluma stars 5BS with a 3/8 spacer .. stock 8.5 rear housing (could have notched further but the wheelhouse would then be the limiter)

running 325/50 MT drag radials

hr bar stops all lean over . wolfe double adjustable CM upper and lower arms so axle is centered and no possibility of any side to side movement (hr braced at lowers) , wolfe adjustable spring perches on axle allow me to dial in close to tire (using 12-150 coil over springs ) . Qa1 adjustables set pretty firm so no worry of squat causing rub on hard launches... and it hooks