C4 Suspension Components in a 1st Gen

[hamrhed97]

With the demise of Wayne Due and his C4 compatible subframe, has anyone here thought about (or actually tried to) modify a stock 1st Gen subframe to accept the C4 suspension pieces? Opinions? My thought would be to see if the C4 "K member" (which has all the control arm mounting points) could be "spliced" into the stock 1st Gen frame to replace the existing frame cross members. More work than its worth? Thoughts?

Hamrhed97
67 Firebird Convertible

[almcbri]

http://www.lateral-g.net/campbell/

http://www.lateral-g.net/campbell/DSCN0097.JPG

Here is a stock frame with C5. I am not a big fan of that mounting point for the LCA's, but here is a frame that has been modified

[Beach Cruiser]

I'm in the same boat as you, I was set to pull the trigger on one of his frames when he closed shop. But I've done tons of research and on the road to building my own frame. First, for what you asked for, the stock vette k member has the engine set back about 6 inches from the camaro location. If you try to move the engine forward with that then you have problems with the rack which sits too high on the vette k member to clear the engine. Most aftermarket subframes use a variation of the ford, (yikes!) rack and pinion because its more compact. I have my design based on a later model mustang rack. I've borrowed different ideas from the various manufacturers to build into my frame. I have it all drawn on cad and am checking the design with the Mitchell suspension software. I'm building the frame jig this weekend. I will post some pics later in the week.

[hamrhed97]

Thanks Andrew for the link to the C5 installation, I love the creativity exhibited by the folks building these cars. I am however focused on trying to use the C4 parts I already purchased.

Beach Cruiser, I have not done anywhere near the homework that you have done. Have you tried to maintain the identical suspension mounting points (UCA & LCA) dimensions in relation to each other? I am anxious to see your pics and follow your progress. Obviously I would welcome any details of your design that you would be willing to share.

Hamrhed97

[Beach Cruiser]

Here's a picture of the two front ends before I pulled the car apart. I'm using the 84-85 components because they are a little narrower than the later years. Mine measures 59.5" hub to hub without the rotors. My camaro measures 60.5" hub to hub. My subframe has been upgraded to 70's vintage Monte Carlo brakes, rotors and Spindles. so the track may be a little different. (I did that in the 80's before all this new PT stuff was out on the market) I havn't gotten all the info back from my friend who is a Nascar Engineer on the new design, but no it's not the same as the stock vette. It's not far off, but I put the roll center about 2 inches above ground. I don't want to send you off in the wrong direction, because I havn't built the subframe yet, nor do I have valid numbers back from my friend. You can check on my progress in the Updates section. I'll be posting some pics tommorrow of the frame jig I built over the weekend.

[Bowtieracing]

This is intresting!!!

I have been wondering the same thing and watched really close this thread with lots of good info : http://www.lateral-g.net/forums/showthread.php4?t=5109

But the question is , how in earth i can fab correct mouting points on old frame when orginal vette part can be used ?? its really easy to miss mount em and get wierd front end geometry and wheel location. I understand at some kind of jig must be made but how how how how :willy:

Something like this i liked to try
http://www.lateral-g.net/campbell/DSCN0097.JPG

[hamrhed97]

Beach Cruiser

Thanks for the picture, I see what you are saying about the stock rack location in the Vette K member. I understand now why Wayne would cut off the stock steering arm from the spindle and bolt on one that allows a lower tie rod attachment point and hence a lower rack position. Are you planning on something similar with your design?

I also have '85 Vette components I am planning to use. I will have to measure the hub to hub distance in my car. The previous owner of my '67 Firebird swapped out the stock front drums for discs from a '72 Nova (I believe). I pretty sure the spindles in my car are the original drum brake parts however.

I wonder if it still could be possible to use the Vette K member (I like the fact that it contains all the correct mounting points in the correct relationship to one another) if you could relocate the rack to a lower position because you are willing to go with different steering arms (i.e. WD's type of set-up)? I don't think that I would be ambitious enough to take on re-designing the suspension geometry. I definitely agree with your approach in building a frame jig and I look forward to seeing the pics when you post them.

Hamrhed97

[Beach Cruiser]

On Wayne's frames (and mine) he mounts the upper control arms on the inside of the pickup points, the stock vette mounts to the outside. Using the stock k member is going to cause 2 problems when you move the engine back to the normal spot, 1st it's going to narrow an already tight spot between the first two cylinders (headers) and the adjustment shims and cross shaft. 2nd, You don't have anywhere to mount your upper coilover bracket because the cross shaft is in the way, and you can't use the stock style spring buckets in the frame for stock spring/shock combo because there is no pocket in the lower a-arm. (also, I doubt it would line up and you will probally have to cut the frame pocket out to get the k member in place.) If you are only concerned about not fabricating a new frame, then make a fixture off of the vette k member to locate everything and cut to fit where it hits on the stock frame. (note: I don't recomend that you do that). You will find that the stock frame rails will limit that fat front wheel/tire combo that we are all after. For the steering, I'm going to use an adjustable bump steer mount on the stock spindle to try and lower the rack some, if I can't get enough out of that, then I may resort to relocating the arms as Wayne did. I think I saw a picture from SEMA of a rack with adjustable inner mounting points, anybody got any info on that?

If there are any of you guys out there are running C4 WD frames, please feel free to jump in and help us out here. I feel like I'm swimming in muddy water, upstream.

Regards,
Mills

[Garage Dog 65]

Hi guys,

I'm doing the 65 porsche coupe. If there is anything I can do just yell. If you modify the stock vette (or any suspension design) specs - that will effect the performance of the suspension. Narrowing the track width does have an effect on performance in several areas due to geometry. It might not be an adverse or dangerous effect though - just might not be the best configuration that provides the best performance at limits. There are several great threads here in the suspension area that I reviewed that provide tons of info - and there are a couple really good books you can read that are also referanced in the threads. Replicating the stock vette locations is pretty easy and can be done low tech like I did - or you can do it using the factory specs and plot the locations. I have those plot points for a C5 cradle from the service manual if they'd help you. You also might check out 21st Century or Morrision for a lower steering arm that will lower the rack position for you. I'm sure someone could build a mount to add a vette cradle to a Gen 1 frame.

Just some thoughts. Jim

[Beach Cruiser]

Thanks for the post, I'm an engineer by trade, so I'm not taking this lightly. There are tons of things to consider on the front of the car, that's one of the reasons I choose to design my own version using the vette components. Changing the track width changes the roll center and a thousand other things, It's all gotta work together. The CG in the camaro is higher than the CG in the vette and a ton of other differences. "suspension engineering" by Herb Adams is a good starting spot. I have a garage copy, and a bathroom copy...:lol:

I really don't think "grafting in" the vette K memeber is a good idea, but I'll buy into locating all the vette components on the stock frame as long as you know what your doing, and do all your homework.

I raised this same question a while ago, but I got some pushback because Wayne was a sponsor, so I dropped it. Caused me to pursue my own path.

Jim,
Love your build, I grimace evertime I have to cut out a rotten panel on my car, and you cut yours completly in half!

[hamrhed97]

Beach Cruiser

I can tell you have done your homework. You point out some clear considerations that would need to be addressed to successfully engineer the adaptation of the C4 suspension parts to the 1st Gen frame. I am also an engineer by trade and I definitely need to do more homework to see if there are feasible solutions to the issues you point out, that would bear out continuing with the stock 1st Gen subframe. Best of luck with your project and I look forward to following your progress.

Hamrhed97

[Beach Cruiser]

Here's some pictures of the frame jig my loyal apprentice fabricator Ed B and I made over the weekend. First we leveled and squared the stock subframe using jackstands and shims. Then we built the jig above it to locate all the body mounts and engine mounts. Keeping the new jig square and level, we built in all the cross braces and knee bracing that you see. Before we unbolted and unclamped everyting, we pulled strings and marked the frame center and the front axle centerlines. these marks and the ground location (with respect to ground clearance at ride height) are what all the suspension pickup points are based off of.

My plan is to remove the jig from the subframe and flip it upsidedown. I'll level it and secure it to the floor so it can't move. Then I'll lay in the frame rails from back to front and square them up. Then I can start locating the suspension pickup points and building the fixtures to hold them in place. I've already built the back half of the frame with the transmission mounts in place, so I'm halfway there as far as the frame rails go.

Hmrhed97 If you'd like to give me a call I'll be glad to share with you what I've learned along the way. pm me for my number.

Mills

Ps, Yes the jig is full of parts of old exercise equipment that I've scavenged over the last month or so. The engine is actually located by the remains of an old stairmaster! You just can't walk into home depot and by any real steel...

[hamrhed97]

Beach Cruiser,

What is the old saying?...Necessity is the Mother of all invention! I'm sure the StairMaster would have been proud to give it's life in the pursuit of Hot Rodding!

I'm going to be on a business trip for the next two weeks, I contact you when I'm back.

Thanks,

Hamrhed97

[Steve Chryssos]

Please note that the modified factory subframe that appears in the Campbell gallery was junked long ago by the present owner. The subframe suffered from a variety of problems. For example, the picture below shows how far forward the rack is located. The steering arms are at the absolute limit of their travel. Less obvious is that the UCA inner pivot points were too high. Fixing the subframe would have required new crossmembers as well as modifications to the frame rails. Since there would be very little OE frame remaining, the decision was made to install a 21st century clip.

I just don't want folks to get the idea that it's okay to duplicate the original Campbell clip.

http://www.lateral-g.net/campbell/DSCN0438.JPG

[Bowtieracing]

Thank you Steve... I had to say the idea looked allmost "too easy" even me. And i was thinking about it...

Sorry for some offtopic but i am still really confused what to do with my front end. I have a good and straigt subframe and i really want to go with 18" x 9,5" to get 275s at front. Sofar my plan has been to go with DSE coilovers,BRP front mount rack % pinion and then notch the stock frame to get more turning angle if needed. Do this sound crazy to you ? Is the total cost too close for art morrison clip allready...:_paranoid

Sorry the ot...

[Steve Chryssos]

My opinion keeps getting me into virtual fist fights with the resident suspension gurus. I'm the first to admit that my viewpoint is based almost entirely on subjective experience.

I get to drive a wide range of cars back to back. Life is good. I'm lucky enough to share shop space with a variety of different pro-touring F-body cars (As well as the Fairlane built by Charlie Libby). I get to hop out of one car and into the next for direct comparison. It's all street driving, but fun and useful nonetheless. Here's a picture:
http://homepage.mac.com/streetfytr/.Pictures/Posting/DSCN1483.jpg
And here's the list:
-Red 69 Coupe: 21st Century C5 clip; one-off torque arm rear, 8 point roll cage, 255/335, aluminum SBC 400, 4L80E paddle shift.
-White 69 vert: Stock clip with full DSE upgrade, ATS spindles and steering box; Hotchkis leafs rear 245/255, 383/T56.
-Green 69: Pro Street. Does nice burnouts.
-Gold 68: Modded C4 tubular clip, full cage, DSE 3" leafs rear; 255/275 all iron 406/4L60E paddle shift.
-Fairlane: Channelled body over tube frame with truck arms; 315's all the way around; 392 Stroker/Richmond 6 speed.
-Blue 68: Just started this one. Will have AirRide Street Challenge kit 255/275 (40's!) Not sure about engine/trans. probably 4L80E paddle shift.

I don't care what any of the "theorists" say about geometry similarities between modded-stock and aftermarket clips. The two clip'd cars (gold and red) are WAY easier to drive than the modded stock clip car. I can therefore drive them faster with confidence. I suspect the difference has more to do with rear-steer steering box (stock clip) VS front steer R&P (aftermarket clip) than anything else. It's important to note that the upgraded clip car (white) is a convertible. Soon I'll have an Air Ride Street Challenge coupe for comparison as well. And some day I hope to convert the gold car to an AME full frame car with 3 link.

If you're doing the welding and fab work yourself and choose quality parts, then it makes sense to extensively mod a front clip as you've described. Just be sure to use ATS spindles. If you're paying for labor, the dollars add up real quick. Even if the difference in cost is $1000, I would still go with an AME or DSE clip.

[Mean 69]

Nice, Steve. How would you describe the difference in driving the rack cars versus the stock frame cars? In other words, "why" is it easier, is steering effort, feedback, combination of all things?

I am looking forward to driving Steve's car with the 21st piece up front. One thing that I can share to the discussion of the front stuff, for certain when I moved from a 235 front tire, to a similar style 275 front tire, the drivability of the car changed a fair amount. Kind of hard to describe, actually, "heavier" feel maybe? The grip level went way up, and on the track (smooth surfaces, fast speeds) it is completely at home, but it does feel different on the street. Not "bad" at all mind you, but different. Sure looks damn cool too.

Mark

[Steve Chryssos]

"Turn-in" on the rear-steer cars feels delayed--not sloppy, like with a stock box, just disjointed. As for tire width, I personally prefer smaller, lighter wheel and tire packages. The Fairlane has humungous 315's up front. even worse, the wheels have almost no backspacing. Their coming off and getting replaced with 275's. Narrower wheels with a touch more backspacing.

[Bowtieracing]

Steve thank you ( and Mark too!!) for good and easy to understand reply and comments.What opportunity to test different suspension choises. Do you have any idea how will BRPs rack&pinion work with stock frame(its a front mount) . You both must be right at wider fronts steering feel might be heavier but i am worried about braking.There are lot of cars with powerfull engines and huge 14" brakes but - cmon!- 245 tires. It must mean something when there is a need for heavy brakeing.

[Steve Chryssos]

.....I am looking forward to driving Steve's car with the 21st piece up front....Mark

You will love the 21st Century clip. Are they outta business? I can't wait to drive one of your 3 links.

[Steve Chryssos]

...Do you have any idea how will BRPs rack&pinion work with stock frame(its a front mount)..

Sorry but I ahave no experience with this product. Anybody measure bumpsteer? Ackerman? Got a link? Until I see otherwise, it comes back to the crossmember being in the way. I just ordered a steering box from Tyler for the AirRide car because I have little faith in the rack conversion kits.

[Steve Chryssos]

Here we go again......
http://homepage.mac.com/streetfytr/.Pictures/Posting/IMG_0284.jpg
http://homepage.mac.com/streetfytr/.Pictures/Posting/IMG_0346.jpg

[Beach Cruiser]

Steve,
I have to take a minute to tell you that your car is the reason mine no longer is a driver! after seeing it in one of the magazines, the bell went off in my head saying "hey, I can do that" now it's three years later and the car is completly apart.... Thanks... No worries, just poking fun.
It must be nice to be able to drive and compare such a variety of suspension set ups, How does the C5 clips compare to the C4 variety? You can see from the prior posts that I'm going down the C4 route. I'm building my own, but mostly emulating the Wayne Due clip you are running. Can you share any insight into the design? anything you would improve, anything that you don't care for? I also would like to replicate your cage, I've read somewhere that the cages must be approved and stamped before you can complete all the welding, do you have any insight into that? Don't mean to Hi Jack the thread, but I think it fits within the theme.
Mills

[Steve Chryssos]

Steve,
I have to take a minute to tell you that your car is the reason mine no longer is a driver! after seeing it in one of the magazines, the bell went off in my head saying "hey, I can do that" now it's three years later and the car is completly apart.... Thanks... No worries, just poking fun......Mills

Mills,
Your welcome and I'm sorry. :lol: I know how the project thing goes. Hang in there and thanks for the kind words. Both C4 and C5 clips work awesome. The biggest concern with the C4 stuff is the available clearance for coil-overs to pass thru the upper a-arms. In order to get the camber curve right, the UCA inner pivot points must be moved inwards towards the vehicle centerline. But doing so consumes clearance for the top of the coil-overs. Correcting this issue requires notching the framerails unless you have the ability to narrow the distance between the rails. It's a compund problem: Your first instinct is to set framerail width such that it is convenient to body bushing placement. You then build from there. LCA placement is next. That is dictated by ball joint position and scrub raduis numbers. By the time you get to UCA placement you realize that you have run out of room for coil over packaging. Bummer.
To avoid this problem, consider sucking in the framerails a bit and leave the suspension where it needs to be. This will help to make rook for the coil-overs. Consider running less backspacing than might seem ideal. That sounds like a compromise until you look at the big picture. LCA placement will move out some relative to the rails and then all is good for UCA and coil-over placement. On the stock ARDF clip they did not leave enough room for the coil-overs so they moved the UCA's out to try and compensate which, in turn, killed the camber curve. And they were stuck running a short 10" spring coil-over. Which was useless since the ride height was 13-7/8" eye to eye and the extended length of the coilover was 14". It's like an Abbott and Costello who's on first skit. In my case, to fix this w/o starting from scratch, I switched to shorter AFCO uppers AND relocated the upper mounts.
As you package your front suspension, try to make room for a coil over with a 12" spring and raise the upper mount. The longer the better. That should help the ride quality. The C5 car accomplishes the same handling and stability with much better ride characterisitics because the geometry is less aggressive. Be warned that you still might need to notch the framerails for coil-over clearance.
Also note that the rack and harmonic damper need to occupy the same space so the engine will need to go back and up. The rack/bumpsteer has been discussed before. But the coil-over concern is more obscure.
I suggest that you purchase wheels, tires and coil-overs as well as hanging sheetmetal before doing any final welding. In addition to the coil-over clearance issue, you might need to "roll" the front suspension forward to compensate for static caster. I run only 3 positive degrees static caster. You might want more.

Good luck and fel free to call me if you need any measurements.

[Beach Cruiser]

Steve,
Thanks for the info, I suspected that the coilover may be a problem with the WD setup, I noticed on several frame pics that the frames are notched in that area. Right now I have my outside dimensions on my frame at 35", but I may be able to move them in a bit more. I'm mock my engine back up with the headers to check clearence issues. My stock hubs measure 60". I was running 15x7 (Z-28) wheels with a 265 50 15 tire, This is almost the same size OD and Width as the 275 50 17's on my late model T/A, I had them inside the fender lip, but just barely. By my calcs, I need to pull the wheels in about 1 to 1.5 inches on each side to clear at all wheel travel positions. I want to run the same tire and wheel as my T/A, (also the same as my wife's vette), The stock offset on the wheels will do this for me. So I have the wheel/tire combo, I also have the coilovers but they came off a WD chassis, so I suspect I'm stuck with the 10" springs, but I can buy new ones.

I'm in the process now of doing the frame layout and the suspension dimensions. I would really like to talk to you about this offline of this forum. Can you PM me with a number and time, and I'll give you a ring.

Mills

[Steve Chryssos]

....I'm in the process now of doing the frame layout and the suspension dimensions. I would really like to talk to you about this offline of this forum. Can you PM me with a number and time, and I'll give you a ring.

Mills

Anytime. Email and phone number are at my website:

http://www.twistmachine.com