Hello to all.

I am currently stripping the entire underside of my '86 Iroc. I want to remove all that crappy undercoating that gets all over everything once a little oil hits it. I am going to POR15 the underside and related parts. Here's my dilemma.

Number one, I do not care for the way Spohn SFC mount or look on the car.

Number two, I don't think Alston SFC will work with my Spohn Torq Arm/trans crossmember set up.

And the last problem is that I have already taken everything off the car. I mean the only things in the car are the fuel tank, rear exhaust section and the differential. It is only a matter of time before I remove them as well. It is my understanding, that in order to correctly install the SFC the car needs to be at curb weight and height. I.E. not up on jack stands and or frame mounted lift.

My questions are these:
One: I would like to find a SFC similar to the set up in the attached picture(Please Ignor notes and or drawings on the picture) or I could buy square tubing. Any ideas?

Two: I want to weld in the SFC(I am leaning towards the Comp. Eng design). Do I have to completly assemble the car again to weld in the SFC??

Three: If you are using SFC can you post what your's look like once mounted?

Thanks to all.

 

You do have a big dilemma then-Why?- Because the picture you posted that you like so much are in fact Spohn SFC's. They are his older "box" design. The newer tubular SFC's mount pretty much identical and are stronger, less weight, and provide even more clearance for the exhaust. Tubular also makes for a better jacking point than the square tube. The tubualr rests inbetween the jack "ears" and will notr slip off sideways like the flat square tube can.

 

Thank you for your response visxtoy. I am glad you comfirmed for me that those were Spohn SFC. As you mentioned, they are the old design(Which I have assumed aren't made any longer, I could be wrong). All of your benifits for the New Design Spohn are certainly important. However, for me, I am not concerned with jacking points, weight, exhaust clearence and the debatable difference between round tube and square tube for my application.

I like the way the square tubing looks and it mounts. It looks beefy. I saw pictures on the Spohn web site of the New Design. I just don't like the way it looks and the way its welded. It looks like it dosen't belong on the car. The old design does.

Thanks for you imput.

 

Unless you spend an inordinate amount of time underneath your car, does it really matter that much what they look like? Personally, I'd be more about the function than the fashion. The square tube may look a little more beefy, but vsixtoy is right- the round tube is a stronger design than the squares. Heck, my ASC installed "SFC's" (if you can call them that) look beefier than just about anything you can buy, but do they work well? Not really...

 

First off, listen to what vsixtoy has to say - believe me he has an extraordinary amount of knowledge about suspension/chassis design etc.

Regarding, the Alston SFC's and the Spohn Torque arm / transmission crossmember etc. They will work together and are entirely compatible. Believe me.

 

just so you know the competition engineering sfc's require floorboard modification. you will need to cut about a 1" x 1' section out of the floorpan.

 

FIrst off thanks for all who have posted. I in no way doubt what vsixtoy is saying. I don't doubt that the spohn's work well. I do doubt that they are a 100% better or a night and day differance over there original design. I have viewed several previous postings. It is my undestanding that the reason Spohn went away from the square tubing was not so much as a improvement in quality as much as it was less expensive and less time consuming to make SFC'c out of round tubing.

drop-top IROC you are right about not spending a lot of time under the car. However, I want the SFC's to look as if they belong on the car. Other people will inevitably be looking under the car. Maybe at the track, maybe I, if hell freezes over, have to take the car to a shop. To me, I believe it is important, what ever you do to your car, it shouldn't look rigged or of poor quality. As it has been said before; If you don't have time to do it right the first time, you defiantly don't have time to do it a second time.

That being said, I have seen some better looking pictures of round tube Spohn SFC's. ebmiller88 seems to have done a very solid install. I even spotted a picture of vsixtoy's under the converter bar install, not bad looking at all. I would still be happier with the Spohn old design but I am warming up to the new design.

Lastly, Dr G, how do you know the alston's will work with the torq Arm/Crossmber mounted setup? I am concerned with the way the SFC's mount to the front of the car. It seems to me that they would interfere with the mounting of the trans crossmember. The Spohn design has a longer mounting flange than stock.

 

we don't you just buy the jegster version which is box tubing from jegs.com i have them and they look just like the picture and i couldn't be happier with them. well made and definately beefy in construction.

 

Now were talking. When you say just like the picture, do you mean the one in my posting?? If so, how did they fit around the cat?

Thanks

 

I have seen Jegs in person on someone car before. I can tell you from close inspection that they hang down noticibly low, they just look to be much heavier (I am certain with assumption they are heavy), they can not be shear welded to the length of the unibody rails because they are not tucked close enough so extra metal stock needs to be fabricated to do so, again adding weight. They have no triagular bracing. Tubular designs reduce twist motion, square box design has more twist flex.

I sound like a PR man for Spohn- but fact is, he makes a great product and I have to support that.

 

I feel the need to comment on the difference between square tube and round tube. The purpose of SFC's is to reduce the twisting of the chassis - a.k.a. torsion.

Round tube has better torsional resistance than square tube. Spohn also went to round tube because the finished SFC's are almost half the weight of the old square tube design.

So, in the end, the round tube weighs less and does a better job in reducing chassis flex. I used to have a set of Spohn square tube SFC's and I sold them and went with the Global West round tube.

One aspect of the Spohn square design I did not like is the triangular brace on the passenger side. You can see it in the pic that was posted. Due to the tight space, the traingle brace has to sit on top of the main tube, rather than butting up to it as it does on the driver's side.

IMHO, this creates a weak link since the passenger side can't be welded as completely as the driver's side.

 

i just thought i'd clarify since i have them. They do not hang down any lower than the basic pinch seam going down the car. and if they do then it is no more than 1/4" on my camaro i can't even see them from the side unless i'm on a creeper essentially. They can be welded going down the pinch seams since they are against them, i believe this is what you call the "unibody rails" ? also they are 34 pounds shipping weight on the box.

 

Thanks for the valuable information. I certainly don't like how you said the passenger side mounts up. I believe that that is how the round tube is intended to mount up. I think it was visxtoy who bent his triangular brace so it butted up against the main tube. I like that idea better too.

xpndbl3 do your SFC have triangular bracing? Also, you say they don't hang down very much at all. How close do the SFC follow the floor pan area? Are there any realy big gaps?? Any pictures?

Thanks for your help.

 

I think someone else already mentioned it, but why does the "look" of the SFC matter? I would be more concerned with how the connectors function rather than how they look. When I made my SFC, I considered function, installation, and clearance both for ground and exhaust. The last thing on my mind was how they would look. And if you use the Por 15 on them, yes I know most SFC come powder coated red, black, etc, and the rest of the underbody, they won't even be very noticable. Unless the person looking under the car is knowledgeable in aftermarket suspension/chassis modification, they won't even notice them. Some people who have been under my car on a lift have thought the SFC were just part of the car the way it came from the factory. That's the best complement a custom job could ever get!!!

BTW, so far everything that I have used from Spohn has been top quality. They are the only ones I use now.

 

92 zzz28 how the SFC look is very important to me. I guess you couldn't tell from my postings.:shrug: As I had posted earlier,
I am warming up to the Spohn Round Tube. I have never questioned the quality of the Spohn. I only questioned the way they look. The pictures on the Spohn web site make the SFC's look like S**T. They look like they are rigged onto the car.

Unless I see documented and verified results that round tube is substantially better that square tube I am going to keep my options open. I don't disagree that round tube has its advatages and probably is better. But the real question is how much better? I mean lets be honest, what percent better could they be in this application? And if square tube is so bad or doesn't work in this application, then why doen't somebody stand up and say all square tube SFC's are junk? Don't just be close minded and jump on the bandwagon because everybody else says "round tube is better case closed."

I am going to keep my options open and eventually buy whichever SFC's which work well and will mount in a professional quality manner. Even if nobody else sees how the SFC's look once they are mounted, If it aint right, I'll know.

 

I made my SFC out of square tubing. I think the square or rectangular blends in better, plus its what I had at the time. I would have had to wait for a few weeks to use round tubing. However, my results were as I imagine all people who install SFC find, like a different car. So good luck to you with your decision making. I think you will be happy with whatever you decide because SFC make a profound improvement on our cars...

 

Sorry about jumpin' the gun on ya. I interpreted what you were saying as a slight against me not liking the round SFC's. I was wrong. Thank you for your input. I am glad to hear that someone fabricated their own SFC. I may be going that route. What size square or retangular tubing did you use. And I am glad to hear somebody else likes the SFC to blend in better.

 

I'll add my .02, I just installed the Alstons on my T/A. The cups don't fit very well. The front cups are welded on the tubes at the wrong angle, making considerable gaps to fill. The rear cups are too wide at the top, again making considerable gaps to fill. Some of the gaps will have to be filled with a stick welder because of where they are located. All in all, I wish I would have went with the Spohn's...... although I too am not very fond of the passenger cross brace.

 

I used 2" square tubing with a .188 wall. Its pretty thick and they were pretty heavy when we had them mocked up on the floor. But that is good weight, all down low!! They extend about 1/4 inch below the rocker panels and I welded them to the rockers completely. None of that every 3" crap!!! I did have to cut a slot on the passenger side floor to make room for them, but it was no biggie. Then we used some floor board scrap from another project to seal it up. Can't see it under the carpets anyway, right...All in all, it turned out pretty well and I am very happy with the performance of them. BTW, this was done about 4 years ago. We did another Camaro, 88 IROC, at about the same time using 2 x 3 rectangular tubing with a .137 or something wall thinkness. Sorry I can't remember exactly. They went in about the same way except we made a crossmember that went where the back seats sit, you know that area where the floor rises. His car was going to be a race car, mine was and will be a street/strip car. I didn't want to tear up my floors and go to crazy, with his, he didn't car. I didn't do all the work on his, just helped with the SFC and fabing the roll cage. We cut slots down the length of his car on both sides to fit the SFC, on mine just a small slot on the PS. YOur options are pretty much wide open. MOstly depends on how much time, money, and skill level you have. BTW, I am not a professional fabricator, I just really enjoy doing it! GOod luck...

 

I like the sound of the way you did it. Any pictures??

 

THere are some around here somewhere...

I wish I could put some here but those pics were pretty old. I will go over to my buddy's shop tomorrow and see if I can throw the car on a lift for a few minutes to snap off some new pics just for you!!

They are here, some link that had a lot of pics of SFC. Happy hunting!!!

 

for documents and verified results refer to any strength and materials book and it will tell you a round design has better torsional properties (material of circular design will not warp like a rectagular design). this isnt about personal preference or perceived improvements - it is knowledge in the engineering community and can be seen in a lot of structures. just look at your driveshaft - it experiences torque similarly to the unibody and is a circular design (this is also influenced by the fact a circular tube of the same radius as a rectagular tube has less mass).

i also believe square tubing is cheaper than circular which may explain its common usage but i am not 100% sure on the pricing.

 

If we're talking about looks... the tubular looks far better IMO, and anyone that is looking under your car and knows what SFCs are will know that tubular is beefier.

If you want a stock look, order them bare and paint them with undercoating or flat black. Or let them rust; whichever.

 

As far as strenght look at roll bars and cages, and race rules.

NHRA, IHRA, NASCAR, etc the rules states roll cages must be round bar with X thickness wall, and X dia.

there's a reason for that..

Look at nascar cages.. They have to keep the drivers safe in 140-195 mph crashs into other cars or the outside wall

There's a reason for them being round.

A tube is a stronger design.. It takes almost double the wall thickness for square to be as strong as round.

 

That cross brace has to be designed that way because of all the different senerios with exhaust routings and replacement catalytic convertors on so many different cars. It had to be made a "one size fits all" design.

If you have just a little creative fabricating skills (creative meaning finding any ol thing to cut and bend it without a tube bender to get it to fit snug- I used sand inside it, two bricks, and a car tire so I didn't have to run across town to a buddies house with a tube bender) you can get it to possibly fit your perticular application a little better. I have a single Cat exhaust that is also tucked up to the floorboard very snug so I had to bend mine regardless. Even straight across layover fitment like it was intended would not work on mine. Mine does now arch up over and ties directly into the passenger SFC and the inner subframe. It is also welded to the passenger floorboard at the center of the arch. Look closely in the picture and you can see where it ties into the SFC- also you can see a few of the increment welds along the SFC's-most of them are hidden behind the radius of the tube out of sight.

 

Thanks to everyone who has replied to this topic. You have provided a lot of very useful info. However, nobody has responded to my second question.

Thanks, Keep up the good work.