coil over suspension with stock K

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Agent_Orange

Agent_Orange

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I shot hemi denny a question regarding this, but thought I would let everyone throw their two cents in.

I was wondering if it would be possible to run a coil over set up with the stock k member.....

Say you beefed up the K and fabricated LCA and UCA's to accept the set up. then went with a tubular upper shock mount like HemiDenny makes. Would something like this work or would the factory K member not allow for proper geometry.
 
Let me add to why I'm asking such a question....I have this idea running bouncing around of building a corvette slayer for under 10 grand. I completely restored my duster around 12-13 years ago. And including the price of the car, I have right around 6g invested into the car. So now I kind of want to play a numbers game and see if it's possible to build an engine and suspension set up that can consistently beat a corvette at auto-x. That would leave me 4 grand to play with. which I'm thinking half of that would need to be allocated for minor engine upgrades.
 
Sure you could buuut...the issue is not the K-member as it is not likely going to be a significant part of the equation. The likley conventional location of the coil-over mount points are going to be the LCA and some point up above the UCA that has to be fabricated. This upper mount has to be joined to the subframes to carry the load that is transmitted up through the coil overs and to the frame. This will be in the area of the inner fenders, not down in the K-member. The K-member will have to stay and be modified to hold the LCA back mount in the proper locations, but the big deal will be fabbing the upper mount and modding the inner fender area for this. The LCA's wil have ot be new too, most likely, since the load carrying point is different from the torsion bar design.

Just my view: The torsion bar design has good linearity and thus can be matched pretty well over the full range of motion to the shock. The stock shocks are kinda short, so could stand a different upper mount to allow a longer shock and thus better heat control and just generally better design parameters and better shck choices to work with. I would keep the torsion bars if I could and mod the shocks and their upper mounts.

The one disadvantage of the torsion bars is ease of tunabilily; the coil-overs DO have it all over the torsion deisgn there. But, once you tune it in, you probably will not mess with it much; it is not like you are going to a dozen different tracks, is it?

I would first invest time, effort and $$ into the REAR on this car, not the front. That is where the Corvette has it ALL OVER your car. This will be tough to match without going to a full independent rear. Without goigng that far, IMO, the best thing you can do it to:
- Use a live rear axle that will live with your power. The lighter the better. I would seriously consider the Toyota Tacoma or earlier rear axle if the HP is not too much. You can get all the gears and posi's for these cheap, and they can handle decent power and are light.
- Modifiy the rear to a 4 link; this will require the rear floor to be highly modded.
- Use the coilovers, but for this strut tower sill have to be built in the back; more serious mods.
- Add a panhard rod for sure (track bar)

Then, of course, you add anti-sway bars, etc, on both ends.

The above is fairly radical but the rear suspension and handling is the weak area. If you don't do the rear coilovers and 4 link, at least go to mono-leafs in the rear; they have better linearity and thus can be better matched to the shocks, and definitely add a panhard rod; these cars need this badly.

You asked for opinions and you got one! (BTW, I have designed both front and rear coilover setups, all for rough road handling in rally use. So this ain't 100% new to me....) Sound like fun, but not a $4k thing unless you can do a lot of the fabricaiton yourself.
 
I would not be going to a bunch of different tracks. just local auto x at the tire rack in south bend, in. which in my opinion is one of the faster, more open auto cross tracks that I've seen. I just thought that 4 grand would make for a nice, even, and relatively affordable number for most people. and the idea of a 10 grand corvette slayer sounds cool. lol I was talking to Denny, and he said about the same thing you did. That there is nothing wrong with the torsion bar suspension. I must admit that it would be pretty cool to see people's reactions to finding out the car is a torsion system still.

Do you think a 1.12 torsion bar, tubular UCA's, better shocks, sway bars and upgraded steering box would be enough for the suspension to hang with a modern corvette?
 
enough to hang with a modern corvette? i haven't done the testing, but its probably a case of close enough is good enough...just build what makes you happy and forget about the dos-equis guy and his yellow corvette.
 
Agent_Orange said:
Do you think a 1.12 torsion bar, tubular UCA's, better shocks, sway bars and upgraded steering box would be enough for the suspension to hang with a modern corvette?
Click to expand...
Not without equal rear suspension work too. I would not bother with the tubular UCA's; keep in mind that these were developed mainly for circle track and drag use and have some strength advantage, but have absolutely zero geometrical advantage over the stock units when put in the stock location. Any UCA's would only be better if they had poly bushings or eliminated some stock UCA flex (of which I am not aware but maybe someone else knows of this).

For the front, my inclination without serious mods would be to:
- Use poly bushings; keep in mind that these will not last as long on the street. These will make the suspension more consistent as it gets loaded side to side.
- Stiffer torsion bars.
- An antisway bar and poly bushings; with the stiffer torsion bars, you will probably not need or want to use the thickest front anti-sway bar.
- High quality gas shocks, like Bilsteins or Koni's
- The steering box sounds good

(Be aware that if you lower this suspension's ride height, then it will throw off the camber a bit; this may work against you or not. The way to most easily fix this is to change the UCA length a bit.)

For the rear without heavy mods, IMO you need to go with mono leafs, gas shocks, anti-sway bar (YES in the rear!) and for goodness sake, install a rear panhard rod! The panhard rod is critical for keeping the rear consistently located under the body and getting rid of time delays while the side movement of the rear axle under body settles out, which ruins fast directional consistency and gives inconsistent tire loading. That is the BIGGEST rear improvement that you can make in this type of suspension for road race or serious auto-x. The panhard rod's chassis connection should have a few mount holes at different heights so you can adjust rear roll center; this is what is done in NASCAR when they 'adjust the track bar' (albeit in just a few seconds!).

What do you have for brakes? These need serious attention for higher speed auto-x.

Aluminum wheels are a must.

Sounds like fun! Enjoy yourself; boy, I could get a lot of suspension with $4k! If yoo imporve the rear suspension, your eyes are really going to be opened.:thumrigh:
 
Agent_Orange said:
I must admit that it would be pretty cool to see people's reactions to finding out the car is a torsion system still.

Do you think a 1.12 torsion bar, tubular UCA's, better shocks, sway bars and upgraded steering box would be enough for the suspension to hang with a modern corvette?
Click to expand...

I would say the Hotchkis parts would be your best bet using the torsion suspension, just follow their A -body build

http://board.moparts.org/ubbthreads/showflat.php?Cat=0&Number=8073886&an=0&page=0#Post8073886
 
I'm sure I will end up spending quite a bit more. there is just something cool about the 10 g mark. I use poly bushing throughout the entire suspension when I restored the car years ago. And I believe most of the tubular UCA's are longer in order to get better caster numbers.

Is a Track Bar really necessary for a solid axle suspension with leaf springs? Don't the leaf springs themselves keep the axle centered? or am I miss understanding the effect of the track bar.

At this point, maybe this is a conversation for a different thread.....
 
I don't know why you think "just changing" from T bars to coil over is going to change handing. The issue is the strength of the front sheet metal which was never engineered to handle the weight of the car in that manner.
 
67Dart273 said:
I don't know why you think "just changing" from T bars to coil over is going to change handing. The issue is the strength of the front sheet metal which was never engineered to handle the weight of the car in that manner.
Click to expand...

No I'm with you there man. I'm not convinced there are enough cons to the coil over system, minus clearance, to make it worth the trouble
 
I tend to agree with 67dart273 and a few others. Modifying just the front end isn't going to cut it in my non-expert opinion. So many other factors like body flex, how your rear end will hook up, etc. I do think a guy could do some pretty cost effective mods to make their car perform and compete. Take a look at the "green brick valiant" Mopar action built. There's even some video's of it against audi's in autocross on youtube. I don't recall the price, but I remember seeing QA1's front suspensions system at sema, and it seemed decent'y priced. I'm beefing up my chassis with subframe connectors and boxing the torsion bars for $65 in material and some time.
 
67Dart273 said:
The issue is the strength of the front sheet metal which was never
engineered to handle the weight of the car in that manner.
Click to expand...
If I'm not mistaken, I don't think HemiDenny's tubular upper shock mount
support system compromises the sheet metal of the front tub directly.
It appears that it does locate to the front "frame rails" and to the thick
(3 layers?) metal at the base of the stock front shock mount. It utilizes
a very heavily made pocket that uses the stock shock mount hole primarily
as a locator only. When assembled it triangulates several very strong points
and is extremely sturdy. It does not transfer the load to the stock upper
shock stud location
 
Agent_Orange said:
I use poly bushing throughout the entire suspension when I restored the car years ago. And I believe most of the tubular UCA's are longer in order to get better caster numbers.
Click to expand...
OK, cool on the bushings! Do you mean 'camber numbers'? An overall longer UCA would change camber, not caster, unless the length of the front arm of the UCA was lengthened by a different amount than the rear arm was lengthened; different arm length changes would indeed change caster.

But you should understand why the tubular LCA is changed from stock before you use it for auto-x. If it's for drag racing to keep better camber when the car's front is raised (to avoid excess negative camber), then that is not going to give you the desired results when the car's front end is lower when diving hard into a corner under hard braking. It is likely to give you excess positive camber on the outside wheel in a turn, which will be bad (assuming the control arm lengths and angles are typical for passenger cars of that era).
 
So besides ease of adjustability what is the advantage of coilovers? Ive never really understood, to me it seems great that the torsion bars send the forces back though the car.
 
My thoughts to try to keep with vettes which was a similar thing wanted to do with my car but plans have since changed, first tires is where the majority of handling comes from you need to fit vette size tires and brakes. Get a proper weight balance and low as possible center of gravity and which is gonna make the suspension work less hard. I see no reason why the rest of the suspension can't be tuned to work.
 
Agent_Orange said:
I shot hemi denny a question regarding this, but thought I would let everyone throw their two cents in.

I was wondering if it would be possible to run a coil over set up with the stock k member.....

Say you beefed up the K and fabricated LCA and UCA's to accept the set up. then went with a tubular upper shock mount like HemiDenny makes. Would something like this work or would the factory K member not allow for proper geometry.
Click to expand...


http://hemiduster.com/coilover.htm

coilovers with the stock k-frame has been done for years. a few places sell the parts to do it.. i know rms sells them and maybe magnumforce. biggest thing is bracing the shock towers because they were not intended for that.
 
^^^ Some reinforcement of the upper mounts even be needed to take the force of a stiffer gas shock like a Bistein or Koni so that the upper shock mount will be stiff enough. Which is one of the points of many is identifying 'frame flex'....I would not do it just becasue of this, but it is something to be aware of.
 
Sure you can, but you can slay just fine with 1+/-" torsion bars and a sway bar. Maybe some adjustable shocks like QA1's?
 
I drove race cars for years and I know by seat time that torsion bars the longer they are like mopar the longer it take to wrap and the longer to unwrap so the control arms are slow to move compaired to coil overs so i'm going with the coil overs and stiffing up the chassis in all the wright places and 4 linking rear and that is because I have drove both
 
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