bobbyc Posted February 8, 2013 Share Posted February 8, 2013 I'm in the process of creating a new subframe for my Z. I've been reading, reviewing, and studying all the z subframe installs I could find. My latest concern is where the front rails meet the firewall. I've seen some where the frame rail appears to be welded to the sheet metal with another piece spanning between the front frame and floor support right behind the tc bucket, and others where the subframe under the floor pans continue up the firewall and tie into the front rails. My concern now is the front rails are a lot more substantial than what they were. If I were in a straight on collision, the rails, if installed like what I have seen, could be coming through the firewall and into the passenger or driver. I want to put a plate on the firewall similar to the plates used on a roll cage. The front rails are 2.5" .120 wall square tubing. What size plate and thickness would be best for this application? I was thinking of something 6x6 in either .120 or overkill with 1/4 plate. Quote Link to comment Share on other sites More sharing options...
Boy from Oz Posted February 8, 2013 Share Posted February 8, 2013 (edited) You need to think carefully about this. . Even back in the Seventies engineers were designing collapsible front ends which are designed to ‘save’ the cabin. The engine and transmission are designed to slide under the cabin and take the frame rails with it, or for them to crumble and absorb the energy. Stiffening a chassis (unibody) might be great for racing but don’t have an accident. The thing you need to remember is that a relatively minor bump may crumble the rail and a panel (repairable) but if you alter the design characteristics you may find major structural and alignment issues occur from even minor carpark knocks. I just replicated the original design. Edited February 8, 2013 by Boy from Oz Quote Link to comment Share on other sites More sharing options...
johnc Posted February 8, 2013 Share Posted February 8, 2013 Plating the connection to the firewall will reduce the likelyhood of the frame rails coming into the cabin (which is already a very low likelyhood). .080" think sheet is plenty thick enough. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted February 9, 2013 Share Posted February 9, 2013 0.12" is about twice what the front rails need to be IMO. 0.065 should be plenty stout and more than the factory had orignally. Cameron Quote Link to comment Share on other sites More sharing options...
bobbyc Posted February 9, 2013 Author Share Posted February 9, 2013 Yeah, I'd agree but it's already done. The difference in weight is only about 4lbs per side. Quote Link to comment Share on other sites More sharing options...
bobbyc Posted February 9, 2013 Author Share Posted February 9, 2013 Would you say it's too thick and I should get new material? Quote Link to comment Share on other sites More sharing options...
nat0_240_chevZ Posted February 9, 2013 Share Posted February 9, 2013 No you'll be fine, But if you did want to replace with 1.6mm thick / 16Ga or 0.063" complete units then let me know, I have got Pics Here!!.......along with everything else available, or to be available soon... I do like What Boy-fromOz has done too, I aggree with John, Re: a comp plate on the firewall to dissipate load around the relatively small back end of the rail-firewall junction. I'll be addressing this issue with an easy to install kit which will mount on the inside of the F/wall under the carpet.......more later Nat0 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.