Subframe connectors - what would you do different next time?

[heavy85]

Holly crap - that could not have hit at a worse spot! I'm really starting to rethink the 2x3 SFC as I think there is a more efficient way to get the stiffness. Been looking around at Camaro/Mustang SFC and most the ones I've found were 2x2 or 2x1.5 albeit .125 wall thickness. Those are more used for drag racing which can put a lot of twist in a chassis ... and are 1000 lb heavier. For the little ole Z I'm wonder if I should take the 2x3 (I already ordered) and cut it in half to make two 1/3 U shaped pieces. Cut off the factory rail (I have to replace my factory subframe since it is beat to hell and back and is pretty much useless now otherwise I'm not sure I would even touch them) and replace them with one of the U's and take the other U and weld it to the inside of the rocker. Then tie in the U at the front of the rocker with a tube diagonally forward to the engine frame rail / TC bucket. Could kill two birds with one stone and end up with the same weight I would have added with just the SFC and not have to disturb my not very rusty floorboards. I'm going to cut out the factory seat brackets to lower the seat and just go with 1x1 directly on the floor. To tie it in even bettey maybe run a couple extra side to side bars from the reinforced rockers to the tunnel with a backing plate to spread the load into the tunnel. This extra bar would be right in front of the seat as high as possible without interfering with the bottom of your legs. What's everyone think? In the end I'm going for as much stiffness and driver safety as possible while minimizing weight.

 

Thanks

Cameron

[Jolane]

Holly crap - that could not have hit at a worse spot! I'm really starting to rethink the 2x3 SFC as I think there is a more efficient way to get the stiffness. Been looking around at Camaro/Mustang SFC and most the ones I've found were 2x2 or 2x1.5 albeit .125 wall thickness. Those are more used for drag racing which can put a lot of twist in a chassis ... and are 1000 lb heavier. For the little ole Z I'm wonder if I should take the 2x3 (I already ordered) and cut it in half to make two 1/3 U shaped pieces. Cut off the factory rail (I have to replace my factory subframe since it is beat to hell and back and is pretty much useless now otherwise I'm not sure I would even touch them) and replace them with one of the U's and take the other U and weld it to the inside of the rocker. Then tie in the U at the front of the rocker with a tube diagonally forward to the engine frame rail / TC bucket. Could kill two birds with one stone and end up with the same weight I would have added with just the SFC and not have to disturb my not very rusty floorboards. I'm going to cut out the factory seat brackets to lower the seat and just go with 1x1 directly on the floor. To tie it in even bettey maybe run a couple extra side to side bars from the reinforced rockers to the tunnel with a backing plate to spread the load into the tunnel. This extra bar would be right in front of the seat as high as possible without interfering with the bottom of your legs. What's everyone think? In the end I'm going for as much stiffness and driver safety as possible while minimizing weight.

 

Thanks

Cameron

 

That's the method I used actually. I put new floors in, then put the stock frame rails in, then a piece of 1 X 3 tubing. I cut a clearance out for the stock frame rails and fit it over. I ran it back to the rear of the floor, then from there fabricated plates to connect to the subframe. I used the same 1X3 tubing, cut it down so it was ~1" tall, and ran two pieces from the tranny tunnel to the rocker, and attached my seats to those. Up front I plated the stock frame rails on bottom, inside engine bay, and top up to the sway bar mounts. I built a new crossmember and welded that in solid, and welded my engine mounts directly to the plated frame rails. Overall maybe I gained 50 punds (complete WAG), but feel like it is nicer and strong. I also welded in two strut braces to the firewall (1 1/4" x .065 tubing), and bolted in a brace across the engine bay. I just want to tie in my SFC to the rocker better.

My main hoop is connected similar to Jon's, although I built a platform for the tube to land on, and boxed it in. My main hoop fit VERY tight to the inner panel.

Joshua

[Guest avriette]

That's the method I used actually. I put new floors in' date=' then put the stock frame rails in, then a piece of 1 X 3 tubing. I cut a clearance out for the stock frame rails and fit it over. I ran it back to the rear of the floor, then from there fabricated plates to connect to the subframe. I used the same 1X3 tubing, cut it down so it was ~1" tall, and ran two pieces from the tranny tunnel to the rocker, and attached my seats to those. Up front I plated the stock frame rails on bottom, inside engine bay, and top up to the sway bar mounts. I built a new crossmember and welded that in solid, and welded my engine mounts directly to the plated frame rails. Overall maybe I gained 50 punds (complete WAG), but feel like it is nicer and strong. I also welded in two strut braces to the firewall (1 1/4" x .065 tubing), and bolted in a brace across the engine bay. I just want to tie in my SFC to the rocker better.

My main hoop is connected similar to Jon's, although I built a platform for the tube to land on, and boxed it in. My main hoop fit VERY tight to the inner panel.

Joshua[/quote']

 

This really sounds like something I need to do to my car (we're at the "tear everything down and get the chassis solid" stage). I know the bottom is beat to hell from bottoming out on things, hopping a curb or two, improper jacking, and that's just the stuff I did (!). Question I have though is, somebody mentioned earlier in the thread that they wanted to make sure they stayed within the rules of some racing body. If I kind of "freestyle" the bottom of the car (the floorboards gotta go, I'd like rails like I've seen in some of these pictures), am I going to run afoul of any body? Are there guidelines to follow?

 

Car in question is an 82 Turbo, with an RB on the way. I've also got to make room for a new diff and things of that nature, and was thinking about diffusers.

[JMortensen]

Car in question is an 82 Turbo, with an RB on the way. I've also got to make room for a new diff and things of that nature, and was thinking about diffusers.

A class that allows an RB in a 82 ZX probably won't have any issues with diffusers, because it's likely to be some unlimited class or other. If you're talking about SCCA racing, you can download the rulebooks online from their website. Start with the rulebook and work from there.

[heavy85]

Sorry to get back on the subject but ..... I just opened the box with the 2x3 tubing in it. Holy heart attack batman that stuff is waaaaaaayyyyyyy overkill OMHO for a Z plus they weigh about 16 lb each side! I've got to rethink this SFC thing because that's just silly beefy (no offense to those who've pioneered this method as it's definitely stout). Maybe I'm over-reacting but those things seen better suited for a truck or something. What about what I suggested a couple posts up and split the 2x3 in half into two 1x3 U pieces and use one half attached to the inside of the rocker and the other half to the bottom of the floor? Then attach the front of the rocker to the engine rail & T/C bucket.

 

Cameron

[Metallicar]

AS my first effort to save a very rusty 2+2, with no expertise in welding, or much of anything else, I decided to do this:

 

 

I used two 1 x 1 x 1/8" box tubes and later welded a 18 gauge skin over the tubes. It is a little hard to make out in this picture but there are 2 tubes, one where the new floor pan meets the rocker and the top one at the top of the rocker box. I welded in intermdiate verticale pieces, making like a ladder. It posed no problems with the seats sliding for and aft. Also I used square tubes to install the seat sliders to. These seat supports were welded to 1/8" plates at the tunnel. This left side progress picture is all I can find at the moment.

 

I thought it might be useful to someone out there in Z Car Land.

[Careless]

any links to this "pete's method" of doing stuff?

[buZy]

Here are mine using a less common but effect approach.

 

[Guest Mike]

buZy... Interesting... I may copy this design but use square tubing and notch a place for the transmission mount to weld into.

[pparaska]

any links to this "pete's method" of doing stuff?

 

 

http://alteredz.com/structuralmods.htm

[Careless]

 

http://alteredz.com/structuralmods.htm

 

 

Hi Pete *waves*

 

I decided to google your name, and found the site anyways =)

 

Nice stuff!

 

I'll be doing something similar, and I'll give you some cred for what i've learned from your site.

 

question.. when cutting the stock rails off. whats the best way to ensure the car stays square?

 

I have four 6 ton jacks that the car is going to be on, so I dunno how I'm going to do the floors, but it's going to be interesting. LOL.

[pparaska]

When I was doing all the work on the front frame rails, I used 6 jack stands, and shimmed between them and the car to keep everything lined up. I also took measurements across, back, down to the floor, diagonal, etc. to document the car's suspension pickup points, and a few other ones like the top of the rail, etc. before cutting. It takes a bunch of time, but it's the next best thing to building a jig.

 

Cheers,

[Careless]

When I was doing all the work on the front frame rails, I used 6 jack stands, and shimmed between them and the car to keep everything lined up. I also took measurements across, back, down to the floor, diagonal, etc. to document the car's suspension pickup points, and a few other ones like the top of the rail, etc. before cutting. It takes a bunch of time, but it's the next best thing to building a jig.

 

Cheers,

 

thanks =)

[LLave]

I was thinking of using 2x3 .065 wall should be plenty strong right?

[pparaska]

The weight difference is minimal between .065 and the thicker gages of wall available. I'd not go below about .08", personally, and might go thicker to .095" or so. You're trading a few pounds here, and the thickness has a large influence on stiffness. Strength is not really a concern, any of the thicknesses available are strong enough, in my guestimation.

[heavy85]

I was thinking of using 2x3 .065 wall should be plenty strong right?

 

I agree with Pete that's 0.065 is plenty strong enough but I was concerned with kinking it with a jack or jackstand or curb etc which is the only reason I went with 0.083. Im my oppinion 0.065 is borderline for that use but I haven't done any testing to prove that out.

 

Here's a crack I found in factory subframe right at the base of the firewall. Appeared to have been jacked by a small jack which caused the crack. If you look close you can see where the were beat up in other places - they actually looked pregnant since the sides bowed out from being bent up by jacking on them .... granted they are a little less than 0.065.

 

 

Cameron