School me on 4 link back half selection

Posted By: Chargerfan68

School me on 4 link back half selection - 12/10/10 06:03 AM

Hey Everyone,

I am going to be installing a backhalf with a 4 link setup on a '68 Charger track dedicated car. I am looking at Chris alston products but would like your advice/experiences on selecting the kit / wheel tubs/ floor material.

I remember reading in "Doorslammers" that it is good if you can retain the stock floor as it acts as a shear plate for strength. Is it possible and/or beneficial to do this, or just fab new flooring with a more race oriented back half setup?

The motor will have about 800 HP with a Jerico and Strange Dana. I may up the anti in the future with a turbo, so that would really lead me to set this up to handle alot more power than 800HP.

Do you think a 32X16" slick with the 4 link could handle the power if the rear was adjusted properly with track time, or I would need larger slicks?

I will have a 12 point cage and the car will be lightened to about 3100 lbs.

Thanks for any and all advice.

I would love to see pictures of your installs and finished products.

Thanks ,
Greg.

Posted By: BIGBLOCK_KAT

Re: School me on 4 link back half selection - 12/10/10 07:46 AM

I ordered a kit from alstons. The quality was good...but the shipping to the east coast was $$ also I ordered their universal 12 pt cage and I was not happy with the fit. Later I went to a 4 link and went with Competition engineerings frame rails and magnum series 4 link kit. Also it's available through summit and tech. supports not too bad. I also had a custom cage built and was very happy.

Posted By: Keith Black®

Re: School me on 4 link back half selection - 12/10/10 09:15 AM

unlawfulracing.com

great setup.

Attached picture 6348713-carwithtankout.jpg

Posted By: jafr

Re: School me on 4 link back half selection - 12/10/10 01:36 PM

You might give S&W a call, talk to Don Schol. If you are not going to build a complete chassis I would definatley leave the firewall in. As far as the floor goes you can take it out, but you need to run your frame rail all the way to where the torsion bars mount and put some X bracing in the floor from the frame rails to the rockers and also put in rocker bars. It will make it a whole lot easier to fabricate,measure and weld. It is very hard to get 100% welds with all the floor in the way. Plus you can mount your belts and seat to somthing other than sheet metal. If you can get ahold of a SFI chassis book that will help you a bunch with what you actually need to make the car safe and certafiable. It will suck if you put a lot of time and effort in your chassis and it won't certify. You might check with some local chassis shops, you might be supprised at how reasonable they are to do a back half.
Good luck on what ever you decide!

Posted By: MR_P_BODY

Re: School me on 4 link back half selection - 12/10/10 01:54 PM

At the weight and hp you should be well into the 9s
so you will be getting the chassis certed so plan on
using the NHRA book and I would advise getting ahold
of the cert book/drawings for at least a 8.50 cert

Posted By: gsmopar

Re: School me on 4 link back half selection - 12/10/10 02:46 PM

Quote:

At the weight and hp you should be well into the 9s
so you will be getting the chassis certed so plan on
using the NHRA book and I would advise getting ahold
of the cert book/drawings for at least a 8.50 cert

+1

I used the Alston frame rails (Ladder bar), but I think there are better options if you're building a race only 4-link set up. I posted my pics below. The chassis work is close to the beginning of the album.

http://s764.photobucket.com/albums/xx281/gsmopar/My%20Car/

Posted By: JERICOGTX

Re: School me on 4 link back half selection - 12/10/10 03:34 PM

I'm installing a Chassis Engineering Top Gun 4 link in my RoadRunner, and a Rick Jones anti roll bar. Doing all the cage, and frame rails my self. Make sure you buy a 4 link that actually has some adjustment to it. The cheap kits have the adjustment points pretty far apart, and could make fine tuning of the suspension difficult.

Posted By: smokinwoody

Re: School me on 4 link back half selection - 12/10/10 07:10 PM

heres a few pictures of the 63 Dodge that Im selling...its in the for sale section under race cars.. http://smg.photobucket.com/albums/v506/smokinwoody/1963%20Dodge/

Competition engineering rails and the 4 links arent made yet, they are their magnum series CM pieces...I tied the front rails with 2x4 rect tubing and the rear rails are 2x3...its now a chassied/unibodied car..as you will see I sliced the stock floor pans and welded the rails all together..

any questions feel free and ask...

Posted By: Chargerfan68

Re: School me on 4 link back half selection - 12/11/10 07:03 PM

Thanks so far for the replies. I am doing more research into your recommendations.

GSMopar: What size tire is that? that looks around the size I am planning to run.

Do I have to consider the front end height at all when designing and installing the rear half? I am currently running the drag race torsion bars and the front , naturally, sits very low. That would change if I ever decided to go with an aftermarket k-frame setup.

Also, does the rear tub and floor work actually replace the strength removed from taking out the "V" brace under the package tray steel and also the removal of the quarter to stock wheel well supports. I understand the rollcage and rails will become one, but I am talking more about the outer sheetmetal to that structure. I don't want the quarters/rear outer metal to move around at all.

Thanks again,
greg.

Posted By: gsmopar

Re: School me on 4 link back half selection - 12/11/10 08:47 PM

32x17.50 When I measured it was the biggest that I could fit without stretching the wheel well opening. At the time I didn't want to repaint the car, but ended up repainting a couple years later anyway.

I had all the same questions as you. This was my first back half and I was probably too conservative when it came to cutting out the rear suspension and floor pan. I did it in probably 15 or 20 different sections carefully looking for tweaks and bends in the quarter panels, rear deck lid, roof, and glass. If I were to do it again, I'd set the car up square on a jig or jack stands and using a plasma cutter take out the entire back half in one big chunk.

This forum was extremely helpful. I have several gigabytes of pictures saved from the board members. Chris Alstons Chassis Works has some good online articles that were also very helpful during the process. Good luck and let me know if I can be of any help. There are more experienced people on this board that I'm sure will chime in as well. Don't forget to take a bunch of pictures!

Later,

Greg

Ride height at rest:

Suspension unloaded:

32x17.5, don't rub:

Posted By: Chargerfan68

Re: School me on 4 link back half selection - 12/12/10 07:00 AM

Quote:

32x17.50 When I measured it was the biggest that I could fit without stretching the wheel well opening. At the time I didn't want to repaint the car, but ended up repainting a couple years later anyway.

I had all the same questions as you. This was my first back half and I was probably too conservative when it came to cutting out the rear suspension and floor pan. I did it in probably 15 or 20 different sections carefully looking for tweaks and bends in the quarter panels, rear deck lid, roof, and glass. If I were to do it again, I'd set the car up square on a jig or jack stands and using a plasma cutter take out the entire back half in one big chunk.

This forum was extremely helpful. I have several gigabytes of pictures saved from the board members. Chris Alstons Chassis Works has some good online articles that were also very helpful during the process. Good luck and let me know if I can be of any help. There are more experienced people on this board that I'm sure will chime in as well. Don't forget to take a bunch of pictures!

Later,

Greg

Ride height at rest:

Suspension unloaded:

32x17.5, don't rub:

Thanks GSMopar,

Your Charger looks pretty awesome. I just want to try and think of everything that will affect the build before I actually start the work.

A few more questions:
1) What guage steel is used for the floor and rear firewall?

2) Did you have to cut any of the inner rear panel (where the qtr window goes) where it meets the wheel tub, or can it be left alone and additional metal to fill it to the tub?

3) What rail spacing did you go with? I am not sure whether to go with 24" or 26". I don't think I will be filling the whole tub width with tire if I go with the 32" tire. Is there any benefit to going wider if you don't actually need such wide tubs?

Thanks...I'm sure I'll have a million more.

Greg.

Posted By: smokinwoody

Re: School me on 4 link back half selection - 12/12/10 12:40 PM

Quote:

Thanks so far for the replies. I am doing more research into your recommendations.

GSMopar: What size tire is that? that looks around the size I am planning to run.

Do I have to consider the front end height at all when designing and installing the rear half? I am currently running the drag race torsion bars and the front , naturally, sits very low. That would change if I ever decided to go with an aftermarket k-frame setup.

Also, does the rear tub and floor work actually replace the strength removed from taking out the "V" brace under the package tray steel and also the removal of the quarter to stock wheel well supports. I understand the rollcage and rails will become one, but I am talking more about the outer sheetmetal to that structure. I don't want the quarters/rear outer metal to move around at all.

Thanks again,
greg.

Greg...after the X braces have been cut, a plate will be welded to the lower section of the "C" pillars and tubes will be welded in back to the frame structure...this will also tie in where the "X" braces were...

it will be a much stronger structure than when it was stock...

Posted By: tboomer

Re: School me on 4 link back half selection - 12/12/10 01:38 PM

I bought a ladder bar setup from Alstons..Very high quality stuff...
http://www.cachassisworks.com/popup.aspx?src=images/Product/large/PKG T.jpg

Posted By: quickd100

Re: School me on 4 link back half selection - 12/12/10 01:48 PM

I know this probably doesn't translate to your car but I built my 4-link from scratch for my truck. I bought Billy Shope's "Mostly Suspensions" DVD. He's very good at walking you through suspension design, theory, and tuning. Dave

Posted By: MR_P_BODY

Re: School me on 4 link back half selection - 12/12/10 01:56 PM

There's 1 word in chassis building that is used all the
time... triangulate... so as you build keep that word
in mind all the time... since your doing the back you
will need to put a X bar in the back... most guys
run it down off the main hoop to the bar that will
mount the upper shocks

Posted By: gsmopar

Re: School me on 4 link back half selection - 12/12/10 05:34 PM

Quote:

1) What guage steel is used for the floor and rear firewall?

I used Chris Alston's kit for the rear firewall and floor. I think it was 16 gauge, but I'm not sure

Quote:

2) Did you have to cut any of the inner rear panel (where the qtr window goes) where it meets the wheel tub, or can it be left alone and additional metal to fill it to the tub?

The front part of the inner wheel well seals to the back part of the rear panel. I had to cut it to fit and seal the wheel tubs, but the factory interior panels still fit.

Quote:

3) What rail spacing did you go with? I am not sure whether to go with 24" or 26". I don't think I will be filling the whole tub width with tire if I go with the 32" tire. Is there any benefit to going wider if you don't actually need such wide tubs?

I didn't buy a pre welded sub frame. I think mine ended up being a little wider than 26 inches, but I don't recall at the moment. I think there is a benefit to going wider on the frame (opposite to what you mentioned above). The car will be more stable as you move the mounting points further apart (shocks and bars, ladder or 4-link). Also, I had very little room left over for wheelie bar mounts on the axle. I probably could have move the frame 2 inches further apart and made things a little easier.

Couple things to consider:

1. Quarter Max, jegs, and a few other companies offer axle mounts for your 4-link that incorporate either the rear shock mount or a wheelie bar mount on the back side. I wish I would have seen these before I started.

2. Seal everything!!! I can't tell you how many tubes of seam sealer I used, but I don't get ANY tire smoke inside the car.

3. 4-link mounts in line with the frame or inside. This is more of an issue with the ladder bar kits, but I'd check when looking at 4-links as well. When your selecting a rear frame, notice where the front bars mount. In line with the frame moves the suspension mounts further out and make the car more stable. However, pay attention to the rest of the frame because this will also decrease suspension travel if done incorrectly.

4-Link in line with frame:

Housing bracket with shock mount:

Posted By: Leon441

Re: School me on 4 link back half selection - 12/12/10 05:50 PM

A 33X10.5W will hook the car with whatever you want to put in it. I would go with quartermax as the shock mount is fixed to the bracket. If the car is set up properly you do not need adjustment those bold holes get disturbed over time. I would go ahead and move up to a round tube back half. You are already talking turbo. And when doing power adders people ussually move up in power pretty quickly. This way you can go 25.2 certification pretty easy. Might as well build it this way to start with. Call SFI a 25.2 spec will cost you $35 and is well worth it. An you cold run faster than you ever intend to at this time. But trust me when you watch your freinds spend money twice to keep up with certification you will thank me for the advice down the road. The package tray bracing is meaningless when the car is built properly like P body said trianulate. No need to X brace if you run a rear halo bar and tube joined across that makes a neater job. Another thing try to pay extra now and get a 4- link with 1/2 inch bolt holes as this will give you far more adjustment in IC.

Leon

Posted By: Chargerfan68

Re: School me on 4 link back half selection - 12/13/10 08:38 PM

Thanks guys. I am looking into everything and gathering some more questions to ask.

One more thing, with the kits, does the rear frame rails end up lining up with the rear stock crossmember? just trying to figure out where it will end up lining up...as I gather the frame rails are installed on a specific angle to the car.

Thanks,
Greg.

Posted By: MR_P_BODY

Re: School me on 4 link back half selection - 12/13/10 10:31 PM

Here's a pic of the back of my chassis... your basically
doing the same thing from the main hoop back

Posted By: gsmopar

Re: School me on 4 link back half selection - 12/14/10 12:09 AM

Quote:

Thanks guys. I am looking into everything and gathering some more questions to ask.

One more thing, with the kits, does the rear frame rails end up lining up with the rear stock crossmember? just trying to figure out where it will end up lining up...as I gather the frame rails are installed on a specific angle to the car.

Thanks,
Greg.

Mine fell short, and my frame should be longer than a 4-link sub frame.

Posted By: Chargerfan68

Re: School me on 4 link back half selection - 12/14/10 10:26 PM

Thanks fellas. More fuel for thought. I really like that tube frame PBody, and I am ordering that SFI Spec...Thanks Leon.

Greg...I was actually talking about the height that the frame rails would meet the tail panel. Does it line up with the structural rear cross member in the tail panel, or higher/lower. Just thinking about what I weld it to if it is not lined up with the inner crossmember.

Thanks,
Greg.

Posted By: Chris Vanover

Re: School me on 4 link back half selection - 12/15/10 01:20 AM

just buy some tubing and make it your self... the ones i have put in the frame rails came up high enough to attach to the rear panels.... weld some 1/8 plates everywhere on the body where you attach the frame rails and such to for strength. 6x6 is good for the rear and what ever will fit on the rockers.. if you do go with a kit look into the round tube ones. and dont cheap out on the rod ends... there not cheap.

Posted By: gsmopar

Re: School me on 4 link back half selection - 12/15/10 03:21 AM

Quote:

Greg...I was actually talking about the height that the frame rails would meet the tail panel. Does it line up with the structural rear cross member in the tail panel, or higher/lower. Just thinking about what I weld it to if it is not lined up with the inner crossmember.

I guess I got lucky. Mine lined up perfect. I did screw up when I welded my mounting plates over the access holes for the reverse lights. Totally my fault, the plates didn't need to be that big.

I recently helped a buddy with a 4-link back half on a 69 cuda fast back. He used a pre-welded Art Morrison kit, and it also lined up to the rear cross member and front rockers. Maybe I got lucky twice?

Later,

Greg