Differences to chasis and suspension for Hemi cars

[STXCuda]

Hello fellow forum members, I got a few questions for a build up I am currently doing. I own a 318 powered 1970 Barracuda. I am starting a restoration and will be swapping in the 426 Hemi for a full Hemi clone. What changes do I need to make to the suspension and or chassis to make it "correct"? I still haven't decided on transmission if that adds to changes I will need to make, thank you for any help I can get!

 

[challenger6pak]

You will need different torsion bars, different rear springs, torque boxes, a Dana rear (with 4 speed), and front disc brakes. If you make it 70's period correct, it will not drive, stop or handle as well as a 90's small car. I would upgrade to parts which are better than stock unless you want a totally stock appearance.

 

[STXCuda]

I would like to upgrade to drive like a more modern vehicle but I want to stay within the general setup. I was thinking a 4 wheel disc setup. What else do you suggest suspension wise?, AND my biggest question, what is meant by torque boxes? Are the rails boxed in or is some sort of reinforcement added to the frame rails on the unibody?

 

[STXCuda]

Ok, I googled it. They basically tie the rear rails to the floor and rockers. I was also considering subframe connectors. Any one have experience to tell me if I can do both?

 

[burntorange70]

Yes you can do both. If you do connectors the boxes will not rely be needed though.

 

[Chryco Psycho]

the factory suspension can get you a long way , it one of the best designs for the period , much larger T bars around 1.1 " , hollow sway bars with a larger diameter , better shocks like QA1 or Bilstien , preferably adjustable , poly bushings , I usually install C body tie rods , depending on rims you can go to larger disc brakes , multi piston calipers , hydro boost will all help braking . Chassis stiffening firewall braces , Torqe boxes, sunframe connectors , lower rad support brace all help , installing lower control arm plates or making them as I did will stiffne them also better adjustable caster struts . I am not sold on tubular upper control arms , they are lighter & can improve geometery but the often fail around the welds or have issues with the heim joints .
Brad 70 did a whole rework on his front suspension & improved a lot of deficiencys & improved the handling .

 

[STXCuda]

Thanks for the great input. Chryco Psycho, I went ahead and ordered the chassis stiffening kit from US Car Tool. I am really looking forward to setting that up. I was also considering boxing in my lower control arms. In reference to the brakes. I am all for enlarging rotors and going 4 wheel disc. My question was your suggestion of hydro-boost as opposed to vacuum boost power brakes. Why? I do plan on running a Hemi and I realize the tightness between the booster and valve cover. I was going to use an 8 in dual diaphragm booster to help clearance.

 

[Chryco Psycho]

If you are running power steering the Hydro boost is a no brainer , far better feel & stopping power with the brakes , you just need to tee the pressure line from the power steering & run a return lin back to the pump . This will help with valve cover clearance as well & if you are not concerned with faxtory look is a great upgrade .
Welding the seams of the K frame & re-inforcing the steering box area & engine mounts as well as the caster strut mount & lower control arm mount with washers .
I figured Brad would join this , he used a different spindle & reworked a lot of the geometery to really increase handling , I wish I had done mine the same way .
The US car tool subframe can be a pain to fit , I usually use 1x2" .125 wall tube & just contour it to the floor , sorry I didn't mention this on the earlier post , I didn't expect you to order the same day !!

 

[STXCuda]

Haha, I understand and again great info. I do have a body shop so I do have the ability to work with whatever shows up. I just wanted to minimize the time fro fabbing from scratch. As far as the reinforcements do you mean by welding additional sheetmetal or just simply using a larger washer in those areas?

 

[Chryco Psycho]

it will be far faster to fab subframes from scratch than try it match the contours of the US Tool type & weld the whole lenght .
You need to weld in plates around the steering box mount & left engine mount & just add washers around the caster strut & lower control arm holes .

 

[challenger6pak]

I have not had any trouble with the frame connectors from US Car Tool. I only had to make a couple of changes to them since no two cars are alike.