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]

https://lateral-g.net/campbell/

https://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 : https://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

Something like this i liked to try

[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...

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!