Nice build so far.

How did you measure out where to mount the FC crossmember?

Also, I cant tell in your pictures, what did you use to make up the 20mm gap for the rear mounting of the crossmember? I made some 20mm Thick Steel rectangles that should work on mine, just curious.

And have you test fit the FC front struts yet? I'm doing the same stuff this week, check out my build progress in my sig if you want.

Keep it up man!

 

I positioned the subframe with the FC front mounting hole centerline 1.5 inches rearward of the centerline for the front FB crossmember bolt. There are a few people on here that have done this swap already and that seems to be the general concensus as to where the subframe should be fore and aft. Then just center it in the rails. I spaced the rear about 3/4 inch from the bottom of the rails and I made templates and cut 1/8 inch plate to fill the gap. That's why you don't see the gap between the rail and the subframe. I then welded everything in. I welded it for extra stiffness and strength and I don't see ever having to remove it. I did the same for the outside of the rails. Cut plate to fill the gaps between the subframe and the rails and welded it in. I'm going to seam-seal eveything before paint.

I did play around with the struts enough to find out that the FB strut tops do not fit FC struts. I had heard a few people say they would but the struts are too big in diameter to fit through the FB bearings. They could be turned slightly to fit. I've also seen people modify the 2nd gen strut to accept the 1st gen strut tube. This is pretty neat if you want to maintain a somewhat stock appearance. Personally, I want the 2nd gen stuff as obviously stock appearing isn't a concern. I ordered a set of FC camber plates off ebay and I'm going to modify my strut towers so they will bolt in. I may also raise my strut towers if I don't have enough suspension travel as I've lowered my car so much. I'm pretty sure bump steer correction will also be needed but I found a couple kits for around 110 bucks.

I had to order the bolts to mount the struts to the knuckles and that stopped me dead im my tracks! Should be here today or tomorrow so I can get back to it. I'll post pics as progress continues.

Good luck!

 

While your waiting for your camber plates, make life easier on yourself and cut and paste the strut tower mounts 1" higher. I used 1" flat stock and bent it in the shape of the strut mount perimeter and welded it between the chassis and the strut mount.

FC strut tops do fit rather easily. just elongate the holes and tack in a washer.

 

Except, I may have to go more than 1 inch. the car sits easily 3 inches lower than stock. I'm going to wait and get everything to mock up then I'll decide how far to raise the strut tops. Looks like I can go almost 3 inches without hitting the bottom of the hood. I'll do the fronts same way I did the rears, like you said cut the top and raise it up.

Thanks for the comments/suggestions. Keep em coming!

 

Looking good! Where did you find bump steer eliminators for $110?

 

I found these. Looks like they should work

http://www.meganracingperformance.co...-p-233006.html

 

Got the control arms hung and put one side together to see how things lined up. It's just hanging in the FB strut top by the nut. Looks like everything will clear even without the rotor on the hub. I am going to add 3/4 inch spacers but that is a lot better than the stock setup. Looks to be pretty centered in the fender. I'm happy.

I still have to get springs and the camber plates are supposed to be here tomorrow. I will also have to put longer studs in the hubs. Still have a lot to do but it's coming together.

 

My car is lower than 3".

I have 2.5" freeboard between the bottom of the FC x-member and the ground.

My FB racecar was as low as I could go and still remain legal on the track.

I never bottomed out my AGX and the 1" raise. The tires would hit the upper frame horn or the frame would hit the ground before the strut would bottom out.

If you put the tops up 3", perhaps you should install a new bumpstop to make sure you don't send sparks down the street on large bumps!

 

After mocking everything up last night, you are right. An inch should be just about perfect. The FC struts are way shorter than the FB struts. So I guess thats the next fab project! Thanks for the advise.

 

Thanks for the link, the only set I knew of was from Mazdatrix, but they are significantly more money. I'll have to give these a shot when I get some extra money.

 

I got the camber plates installed today. I used the FC camber plates to mark the holes. A rat tail file elongated the holes quite nicely. Took about 10 minutes per side. Very easy. I mocked up the rest of the suspension and put the wheels back on. At full bump the control arm is angled up slightly. At ride height they will angle down just slightly. They increase in negative camber the more they turn. I still have to connect the swaybar, and the column and linkage for the rack. It's strange to see a rack and pinion after looking at the loose stock steering for so long.

Looks like it's back to bodywork. Unfortunately. I hope to be ready for paint by mid June.

 

Looks like it fits well, sorry if I missed it, but where are those camber plates from? I guess you decided not to raise the towers?

 

I got them off ebay. They were pretty cheap. I am going to raise the towers. I'm going to cut the mounting plate off the top, raise it up and weld plate in. Like I did on the rear.

 

Ah ok, that's what I thought you had said you were planning to do. I'm thinking I should do the same on mine as my setup puts the FB strut pretty low in it's travel. Then again It doesn't move a whole lot in the first place so I"m not sure how big of an issue it is.

 

I would have had to raise it with the GSL-SE stuff I had as well. At ride height it only has about an inch and half of travel before it bottoms out on the snubber. The bottom of the coil is going to have to stop just above the tire so it won't rub. So, it looks to physically fit some coil sleeves and coils on it I'm going to have to have at least an inch if not 2. I might just go 2 inches. I'll use a longer snubber to limit the travel.

 

One other consideration I'm contemplating at this point is actually cutting the rail sections with the welded in crossmember and moving the whole thing up about 2 inches to raise the roll center back up to what it needs to be. I'd like the control arms to be angled down slightly toward the wheel at static ride height. This results in a better roll center and less bump steer and camber change through the suspension travel. It won't be a small job but at this point I think it would be a good thing in the long run.

 

Peejay was saying he'd wished he'd done that on his as well, rather than spacing the rear of the subframe down, section the front of the FB frame so that the subframe was raised up.

Can't say I know enough about it to comment one way or the other, at this point the little bit of bump steer I've got should be alleviated with those bump steer correcting tie rod ends (once I buy them that is) Otherwise I'm quite happy with how mine has been working so far Then again I'm not racing the thing.

 

Ok, here is what I have planned to cut out. I'll move it straight up and weld it back in and plate it with some steel. I welded some additional bracing in to hold it while I get it moved.

 

This is what prompted this change. The control arm and rack tie rod are both angled up at static ride height. I want them angled down slightly.

I've spent the last 2 nights cleaning the frame where I'm going to cut. 30+ years of gunk but surprisingly little rust. This car is virtually rust free.

 

another option would be to score some s4 arms and space the ball joint until your satisfied.

Might be easier.

You also gain easier replaced ball joints!

 

And that would help get the roll center closer to the roll axis of the car. The problem though is lowering the arm wouldn't help correct bumpsteer or increased camber changes. I laid this all out on an NX CAD system and animated it. (I am an Engineering Designer) Here are my conclusions based on that.

I need to raise the pivot point of the arm in relation to the spindle height. The arm at the lower limit swung through an arc to the upper limit creates an angle controlled by the suspension travel. Ideally the spindle should sit in the middle of this travel. At ride height the arms are angled slightly up throwing this angle almost entirely to the top of the spindle. Raising the pivot point will swing this angle back down.

I'm going to set it up so that at street ride height the arms are angling slightly down. Then when I want to set it up for autocross I can lower it with the coilovers and everything will be nicely neutral.

So hopefully everything will work out cause I'm a little nervous about cutting the rails.

 

I ran my FB Race Car with a 1" spacer between the ball joint and the arm as a test.

To be honest, yes the roll center isn't where it should be ideally but then again, it isn't on an FC either.

I didn't notice any severe driveability issues on the track. The car didn't feel like it wanted to pitch up and steering push/pull was predictable. I was running some fairly wide and sticky tires to that may have shadowed any deficiencies in the suspension.

I would be reluctant as you are to cut the frame rails, although, i didn't have much of a rail to re-weld to as mine was rust. I would also check with whatever track you may be running and see if the tech inspection is strict. some tracks are really lenient and others as for urine samples! IOW, some may frown on cutting unitbody frame extensions as you are thinking (or by now, have done)...just a thought.

 

I struggled with this on my old Fox Mustang SCCA Solo car. It had a suspension that is pretty similar to the FC. My solution was to build 2.5" drop spindles. This allowed the car to sit 3.5" lower than stock without throwing the suspension out of geometry. I did this by replacing the lower ball joint with a 3/4" spherical bearing, drilling the tapper out of the spindle, welding a 2.5 spacer to the spindle and using a long 3/4" grade 8 bolt to hold it all together.

In hindsight, moving the control arm inner pivot points would have been a better way to go with that car.

If you add some additonal struture to the car what you are doing should be fine.

 

Thanks for the comments guys. The more the better.

Still no rust. Not even inside the rails that I can see. I'm amazed that a 1981 car has no rust here in the Cincinnati area. It's the cleanest old car I've ever seen. Try to find an 81 camaro with no rust.

It's too late to turn back now. I started cutting then realized I only had three cutoff wheels. I'll run out today and get some more. I want to get this done in the next week.

I'm going to box the rails at the cuts with 11ga And tie the strut towers into the rails as well. When I get done with this I still have to raise the strut tops.

I'll post some more pics when I get a chance.

 

Very nice body work. looks good