Best Coilover IFS for '71 duster?

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Mopar Nate

Mopar Nate

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Need any advice I can get for aftermarket front suspensions out there. I have looked into the HDK setup and it seems solid, but with so many options I just want to hear some reviews and not leave any stones unturned. I know there are plenty of threads out there but "each application is different" is about all that's said so.. here goes: goal is (don't beat me up too bad here) a lowered, slightly cambered, handling machine. I have a built matching 318 (for now) and am going to pick up a ford 8.8 IRS system in the A.M. also looking into the t56 conversion. I have an rx8 as a daily and absolutely love the handling in that car and am looking to match it as closely as I can. PS option is a must for me, quicker steering ratios are a plus, rack and pinion, header clearance for an over-budget exhaust system, and tunabilty is a big aspect as well. Any help would be appreciated. Thanks in advance.
 
What budget?
For me I would replace the front frame rails... well honestly the whole frame and put a good front clip in like a Vette unit. I am sure replacement mopar specific units are good but if I was going to build a g-machine I would go a diffrent route.
 
Every application IS different.

And if those are your goals, they can be accomplished with a torsion bar front suspension for thousands less than a coil over conversion. There's a member here that has turned faster times at the Goodguys autoX events than cars with full Art Morrison chassis', and he was running a lightly modified front torsion bar and rear leaf spring set up, only minor upgrades from stock really.

Run a Borgeson/Delphi steering box from Bergman Auto. With a small block you can run Dougs's or TTI headers without any issues. The T56 will be a hydraulic clutch anyway, so no linkage to worry about. Grab a set of 1.12" torsion bars from Firm Feel and adjustable shocks from Hotchkis. The suspension will be easily adjustable for height and shock dampening, you can run 13" brakes from dr diff, and you can fit a wider tire up front than you can with the coil over conversions.

The torsion bar design that our cars have is a good one. The factory undersprung these cars and ran the ride height too high, but those are easy fixes. There's nothing magic about coil overs, they're just springs and shocks.
 
The budget isnt a massive one by any means and price is a factor. That being said I'm not looking to finish the car anytime soon. I have family members who can assist me with most fab work. Im not really building a race car but I do want it to perform. As for the torsion bar set ups... the big thing for me wasnt so much the handling ability... because i know they have the abilty to, for me its the shotty steering feeling from the conventional steering box i feel like the feedback from the road is nowhere to be found unless I hit one of these famous SC potholes. Id like to pull some weight from the front end if possible & have a larger aftermarket to shop in.
 
Mopar Nate said:
for me its the shotty steering feeling from the conventional steering box i feel like the feedback from the road is nowhere to be found unless I hit one of these famous SC potholes. Id like to pull some weight from the front end if possible & have a larger aftermarket to shop in.
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I'm guessing you have a stock power steering set up?

The stock power steering is pretty overboosted, that's well known. I went to a 16:1 Flaming river box, definitely no issues with feedback there. But you should look into the borgeson power steering box from Bergman Auto Craft. Its a later model power steering box set up to work on our cars. I believe the ratio is 14:1.

Another option would be to use a steering quickner on a rebuilt stock box. I've definitely given that some thought. The Hotchkis Challenger uses one. You can get a Howe 1.5:1 steering quickner, which would put the ratio at 12:1 for the stock box. I bet that would take care of a lot of the road feel issues.

The aftermarket support for these cars is constantly growing, especially regarding the suspension. A lot of the stuff out there now wasn't around even 5 years ago.
 
Playing devils advocate for a moment.. if the steering style we have is easily fixed... why the big outcry for rack style steering mods? If they are so equal why are so many people throwing out nearly $5k on a different system? I was under the impression the only answer was rack & pinion from reading on the forums. I know our stock steering and suspension is very misunderstood but is it to the extent that this coilover ifs thing is just because its what most prople are familiar with?
 
Hi Nate,

For me, some 20 years ago, it was about the room. There just was no way I could install a Hemi under the flat hood of my green Duster unless I got rid of the steering box.

installing a rack made sense, but I was even more pleasantly surprised to find out how much better the steering responded....it was a win-win.

then came the front end geometry....in order to get suitable geometry with a rack install utilizing the factory UCA pivots and frame rails....I had to relocate the LCA pivot,.....hence the torsion bars would no longer work. Being forced to a coil over, once again I was pleasantly surprised by the room and header choices now available.....not to mention ease of install and eliminating rubbing / clearance issues. I would be perfectly happy with torsion bars but they simply will not work because of the new pivot location required by the rack install. but again a win-win.

you could go either way....depends on if the benefits (added room / expanded exhaust options/ 30 lb weight drop / narrow track width /lowering capabilities) afforded by the rack / coil-over conversion is worth the additional money you would spend on a stock beef-up / rebuild....... at least there are choices, and that is a good thing.
 
Thanks Denny, with the coil over/rack systems.. when/if parts break or wear out is there options for these systems or are you limited to the original custom stuff? I want the most out of the money spent either way.. and clearance for my long tubes would be a plus. Also what are the camber/caster/toe adjustment abilities of the systems in general? The engine in this car is going to be in and out frequently if I have the crowded engine bay that's stock... just for my own piddling and learning so I'm leaning towards getting rid of the torsion bars and cleaning the bay up to do the work in the car.
 
Mopar Nate said:
Thanks Denny, with the coil over/rack systems.. when/if parts break or wear out is there options for these systems or are you limited to the original custom stuff? I want the most out of the money spent either way.. and clearance for my long tubes would be a plus. Also what are the camber/caster/toe adjustment abilities of the systems in general? The engine in this car is going to be in and out frequently if I have the crowded engine bay that's stock... just for my own piddling and learning so I'm leaning towards getting rid of the torsion bars and cleaning the bay up to do the work in the car.
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Other than the fabricated pieces, the HDK uses (high quality) UNMODIFIED, off the shelf, ball joints, spindles, racks coil-overs, springs, tie rod ends, steering shaft universals/ vibration dampners.

The HDK features adjustable length UCAs AND LCAs. Additionally the upper ball joint location is slightly offset allowing greater adjustment by changing side to side or flipping it upside down. Combine that with the 1/4" aluminum spacers for both sides of the UCA poly-ends that can be stacked on one side if needed.

what this mean is you have all the adjustment possible from a street spec to an aggressive autoX alignment......all while keeping the suspension fluid without any binding.
 
Mopar Nate said:
Playing devils advocate for a moment.. if the steering style we have is easily fixed... why the big outcry for rack style steering mods? If they are so equal why are so many people throwing out nearly $5k on a different system? I was under the impression the only answer was rack & pinion from reading on the forums. I know our stock steering and suspension is very misunderstood but is it to the extent that this coilover ifs thing is just because its what most prople are familiar with?
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Honestly?

I think that most people swapping to coilovers and racks have no idea how torsion bar suspension works. Or, for that matter, how coilovers and racks even really work. It doesn't help that the factory slapped in ridiculously soft torsion bars and that the stock handling of these cars is miserable. Add to the fact that a lot of these cars are bought needing a full suspension rebuild and are worn out and wobbly. So, guys buy into the advertising about how great the coilover conversions are. And hey, it costs $5k, it has to be the best right? And it bolts right on! It's easy!

Proof of that is the fact that you read some forums and think the "only answer" is rack and pinion steering. That's just magazine racing at its best. Yes, a brand new rack and pinion set up gives a nice steering feel. But its just physics. Find out the ratio and amount of boost. Racks wear and get sloppy too. Are they better than having pitman's and idler's and all that linkage? Sure, they are. Is it worth spending $5k on a front suspension conversion? Not even close, at least in my opinion. But I'm just a cave man that likes manual steering. Yes, my 16:1 manual box makes turning my 275/35/18's kind of entertaining at parking lot speeds. But at anything greater than 10mph its great, and if I wanted a nice, easy to drive car I'd buy a pree-***.

There are absolutely advantages to the coilover conversions out there. Denny builds AWESOME stuff, and he knows what he's doing. So does Bill over at RMS. And for some folks I think that really is a good way to go. If you're really yanking your engine out every week, it might the right thing for you- I can absolutely say that getting my Doug's headers into my car with 1.12" torsion bars, a Milodon road race pan, poly spool mounts, and a 4 speed was a colossal PITA. But its all in there now, and it doesn't bother me driving my car everyday.

But there are disadvantages to those coilover systems too. All suspension design is a trade off, and anyone that says different doesn't know anything about suspension design.

I just hate seeing guys that think they NEED to have coilovers to have a good handling car. You don't. You can get all of the caster and camber adjustment that you want out of the torsion bar suspension. Sure, it helps to go to tubular UCA's and adjustable strut rods. But if you do that you can set your car up with as much or as little camber and caster as you want. My Challenger is currently set up with -1* of camber and +5* caster, and I could get more or less of either. My Duster has a little less caster with the manual steering, but that's just easier for me.

Ultimately, it really comes down to what you want. Me personally, I'm not going to spend more than twice as much to convert to coilvers when I know there are guys like tomswheels out there embarrassing $150k, art morrison Camaro's on the autoX course. Sure, I bet his car is VERY different to drive than those cars. But its still faster.

tomswheels said:
Hey I know I'm a little late adding my 2 cents, but it really is all about what you want to spend. I'm sure a car with coil overs and a rack and pinion will be EASIER to drive quickly on an autocross, and if you have the money to do it, great. I don't have the money so my 69 Barracuda convertible runs torsion bars, leaf springs, $14.95 Gabriel gas shocks, a firm feel box, front sway bar, and subframe connectors. That's it. Less than $1000 in suspension/steering. At the last Goodguys Autocross in Del Mar it beat the $150k Camaro that just got invited to Optima (Alcala) and Steven Rupps "Bad Penny" Camaro. Just goes to show you torsion bars can still surprise the big-bucks guys....


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It's probably fair to say I haven't given the torsion bar setup a fair chance considering my 71 is the only car I've ever been in with torsion bars and it was far gone when it was handed down to me. I like that both sides of the argument are legitimate and either way I go here there is hope for the handling. Realistically what is the cost of beefing up the stock system? Including tubular control arms and upgrading to bigger brakes (sorry Kelsey-Hayes maybe for the vette guys but not me). Again its tight enough with factory parts I Cant imagine with the t56 and headers and steering box and new clutch pieces to come that I wouldn't prefer the coil over system but for the right price (in savings) I'll fight those pita headers again and keep it on the bars.
 
This is what I would do (and have basically done on my car...)

1.06 (or bigger) Firm Feel torsion bars - $355
Tubular UCA’s (PST, FFI, etc) $350
Adjustable strut rods (PST SR 14385) $279
Solid tie rod sleeves (PST SAS 440S) $49
LCA boxing plate (PST LCAPLTMOP621) $14.50
Greasable LCA pins (FFI w bushings) $135

Hellwig tubular front sway bar 1 1/8” #55906 $231

Hotchkis Fox Shocks (non-adjustable) - $280

That puts you at about $1,700 for what I have listed. You'll still need to add a set of lower ball joints, tie rod ends, and LCA bushings. Everything else gets replaced with the new parts. That's just for the front since you're looking to go IRS in the back.

For steering, the biggest power upgrade out there is the Borgeson/Delphi steering box. Bergman Auto Craft sells them for $695, but then there's some additional costs for the steering coupler and lines. I'd contact Peter for a full run down on that. He's GmachineDartGT on here. http://bergmanautocraft.com/

Or you could just add a steering quickner to the stock power system with a rebuilt box. Howe sells the 1.5:1 steering quickners for $90. Rebuilt power steering boxes are around $360 from Firm Feel. You'd have to do some custom work to install the quickner, but it's not a huge deal. That's the set up that the Hotchkis Challenger runs, and that would get you a 12:1 steering ratio.

Brakes vary quite a bit depending on what you're looking for, but really the brakes are going to cost about the same whether you stick with the stock set up or opt for the coilover conversion. Personally, I'm a big fan of Dr. Diff (Cass Eslick). He has some great brake kits on his website. I run his 13" front "cobra style" disks, which will set you back $850, assuming you already have the later 73+ disk spindles.

Assuming you did everything, including the Borgeson steering box and the 13" rotors, you'd probably be looking at $3600. But that's allowing $1k for the Borgeson/Delphi box and adaptors. You could do a stock rebuilt box and quickner for about $3,100 all in, allowing some money for the steering column mods.

The RMS alterkation starts at $4,250, and that still doesn't include brakes. If you add the somewhat compareable 4 piston 12.19" wilwoods, you're looking at $5k. Not sure how HemiDenny's kits compare to that, he would be the one to ask. I thought his were a little less, but again, he'd be the one to talk to.
 
I dont know the price of Dennys kit bit the alterktion and others are way over priced. AME ifs kit 3500 no bakes bit new frame rails.
The biggest issue I have found with the stock front end is you cant move the engine back, or lower... big block.
 
MidTexCuda said:
I dont know the price of Dennys kit bit the alterktion and others are way over priced. AME ifs kit 3500 no bakes bit new frame rails.
The biggest issue I have found with the stock front end is you cant move the engine back, or lower... big block.
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Just so you know....

The HDK is $2895 for a manual steer (add$100 for power)....includes mounts, spindles, and rack ....but does not include coil-overs and brakes

For additional info, please e-mail me
[email protected]
 
I am in the process of switching to coil overs. For me it was more about the room, weight and engine location than handling.
 
Mopar Nate said:
How does the engine location change? Back forward up down? Or is there like custom mounts?
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I have a standard package.... but I will and have put the motor trans up / down / back / forward.....often at no extra charge.

One of the benefits of no torsion bars and the more compact rack and pinion is the ability to move things around if desired.

Having a hot rod for some of us is like when we were growing up and built everything we were shown in the Erector Set guide.....then it was time to build what we imagined.
 
I think with my needs the HDK sounds like a good fit. I'm still a little ways out from purchasing anything but if I can get this 8.8 to fit then the rest has been done before and I'll have a better idea what to expect. Denny ever put any thought into IRS systems?
 
Ride up to my house four hours from you s nd I will take you out in my duster. I have been on both sides of the fence. The RMS side is better all the way around.
 
Might just have to take you up on that haha. In your opinion what is the benefits of that style system over the other as far as feel and adjustability?
 
Mopar Nate said:
I think with my needs the HDK sounds like a good fit. I'm still a little ways out from purchasing anything but if I can get this 8.8 to fit then the rest has been done before and I'll have a better idea what to expect. Denny ever put any thought into IRS systems?
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IRS....no , but I have the triangulated 4-bar on the drawing board....the early A body is all but .done...the E/B body is at the cutters... after that the 4-bar will happen.
 
HemiDenny said:
IRS....no , but I have the triangulated 4-bar on the drawing board....the early A body is all but .done...the E/B body is at the cutters... after that the 4-bar will happen.
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From what these guys say about your setups will be hard to compete with cars running your full system. Best of Luck
 
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