mobythevan Posted September 11, 2002 Share Posted September 11, 2002 I have to replace my frame in the engine compartment like Pete did because of rust. the cross member currently bolts just to the outside of the tube frame and has some reinforcement in the fender. I plan to replace this with 2.5" square tubing, but what is a good way to remount the cross member since it is just to the outside of the tubing? I didn't get what Pete was up to with the "pockets" for the cross member. I could weld some angle to the side of the tubing for the cross member mount. What have you guys been doing when you have to replace this part of the frame? Quote Link to comment Share on other sites More sharing options...
mobythevan Posted September 11, 2002 Author Share Posted September 11, 2002 I'll look at it again tonight, it just appeared to bolt up more outside. I guess it will make more sense when I get one side cut out and start trial fitting the new tubing. Quote Link to comment Share on other sites More sharing options...
jeromio Posted September 12, 2002 Share Posted September 12, 2002 What Perry said. The stock setup has the frame rails sorta gradually pinched along their length and then the pinch is most pronounced where the crossmember goes. Quote Link to comment Share on other sites More sharing options...
Guest Perry Posted September 12, 2002 Share Posted September 12, 2002 I'd have to look at pete's pics again to know for sure but most reconstructions I have seen fabricate pockets in the side of the replacement tube. The tube is placed flush with the inner fender which would make the crossmember bolts go inside the tube, the pockets are recessed into the tube to allow the crossmember bolts to be accessed. look at the factory setup where the bolts are and you'll see what I mean. Perry Quote Link to comment Share on other sites More sharing options...
mobythevan Posted October 21, 2002 Author Share Posted October 21, 2002 This weekend I made all of the measurements and cut out the passenger engine frame rail. My suspicions were confirmed when I measured and found that if I use 2.5" tubing and align it with the fender, then the crossmember bolt holes are right at the outside of the tubing. You could fix this by moving the frame rail outward, but then it would portrude into the wheel well. To fix the problem I extended the width of the frame rail at the crossmember location and then built in the pocket so the bolts will still drop in. Supposing I would have just put a pocket in the 2.5" tubing, the bolt holes would have ended up with no steel on the outside to support the bolt. All of this was based on stock locations. My measurement showed that the width of the stock frame rail was ~3" including the lip in the fender well. The outside edge of the bolt hole for the crossmember was then ~.5" back toward the engine. Putting the edge of the bolt hole at the edge of the 2.5" tubing. You can see what I did at engine frame rail Does this sound right? I double checked ten times, but maybe I missed something. Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 21, 2002 Share Posted October 21, 2002 That sounds right. I did something very similar on my 2.5"x2.5" frame rails: http://mywebpages.comcast.net/pparaska/structuralmods.htm I also remember that the holes were right in line with the side of the tube and stock frame rail side. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted October 21, 2002 Share Posted October 21, 2002 I have seen some pretty good jobs of stock frame rail replacememt. Would this not be easier? I saw an entire front end get rebuilt from almost nothing.. looked factory when done. Then there is no worries about crossmember mounts. I'd only go custom if I was going to tube the entire front end and do away with all the sheet metal engine bay/towers etc.. Just putting that out that there are options to custom frame rails in the engine bay... just in case someone does a search on this in the future.. hehe Quote Link to comment Share on other sites More sharing options...
mobythevan Posted October 22, 2002 Author Share Posted October 22, 2002 ok, cool. Things are going very good so far. I figure four months of work on the rust. I don't have any other projects to distract from this so we'll see. got to replace floor pans, rockers, and rear quarters. I think i am going to do all of the passenger side first, then do the driver. that way the driver side frame will help stiffen the chassis while I have the floor pans out and the rockers out. think i will use the 1x3 inch tubing to stiffen the rockers as i have seen others do. Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted October 22, 2002 Share Posted October 22, 2002 I recently built a complete frame for my 260Z. The bolt holes are at the edge of the frame as you and pete have already discovered. I built the front portion of my frame to the 260Z drawing, and ended up with the crossmember in the wrong place. The 260Z and 280Z drawings disagree. I believe the 280Z drawing to be correct (at least in the fore/aft placement of the crossmember). How far from the firewall are you placing the rear bolt of the front crossmember? I have had others measure and report a distance of 19 7/8" and 20". Pete, where did you place the crossmember holes? Dan Quote Link to comment Share on other sites More sharing options...
pparaska Posted October 22, 2002 Share Posted October 22, 2002 I put my holes just where they were stock ;D. Sorry, I'll measure soon and get back to you. That 19 7/8" from the firewall number sure seems familiar though. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted October 22, 2002 Author Share Posted October 22, 2002 I'll have to check tonight when I get home. I have all of the measurements in my notebook in the garage. I am sure it was ~20" though. Quote Link to comment Share on other sites More sharing options...
zilverbullet77 Posted May 26, 2015 Share Posted May 26, 2015 (edited) This weekend I made all of the measurements and cut out the passenger engine frame rail. My suspicions were confirmed when I measured and found that if I use 2.5" tubing and align it with the fender, then the crossmember bolt holes are right at the outside of the tubing. You could fix this by moving the frame rail outward, but then it would portrude into the wheel well. To fix the problem I extended the width of the frame rail at the crossmember location and then built in the pocket so the bolts will still drop in. Supposing I would have just put a pocket in the 2.5" tubing, the bolt holes would have ended up with no steel on the outside to support the bolt. All of this was based on stock locations. My measurement showed that the width of the stock frame rail was ~3" including the lip in the fender well. The outside edge of the bolt hole for the crossmember was then ~.5" back toward the engine. Putting the edge of the bolt hole at the edge of the 2.5" tubing. You can see what I did at engine frame rail Does this sound right? I double checked ten times, but maybe I missed something. I know this is an old post but after days of searching for the same info I still cant find an answer to this question. As stated above, the center of the hole on the frame rail / cross member mount location is 2.5 inches from the inside of the frame rail. That means if I use 2.5 wide square metal tubing the hole will be penetrating the outside edge of the tubing. Does this mean I have to use something wider than 2.5? move the rail outward? or weld some type of plate / angle iron to the outside rail? Edited May 26, 2015 by zilverbullet77 Quote Link to comment Share on other sites More sharing options...
Jay Gadsby Posted May 26, 2015 Share Posted May 26, 2015 (edited) I am about to do this same thing. My plan was to weld in a plate/pocket similar to stock, just more square. I was thinking of welding in an 1/8" plate that the crossmember will bolt to and sit under. A small notch cut into the tubing and sealed off with some welded in 16 gauge should be plenty strong. Edited May 26, 2015 by Jay_Gadsby Quote Link to comment Share on other sites More sharing options...
johnc Posted May 26, 2015 Share Posted May 26, 2015 Just weld the crossmember in place. Quote Link to comment Share on other sites More sharing options...
Jay Gadsby Posted May 26, 2015 Share Posted May 26, 2015 Can't tell if serious I suppose after all the rust repair is done, engine and suspension back in, hopefully it would be many years before removing it again. Quote Link to comment Share on other sites More sharing options...
johnc Posted May 26, 2015 Share Posted May 26, 2015 Perfectly serious. Quote Link to comment Share on other sites More sharing options...
Jay Gadsby Posted May 26, 2015 Share Posted May 26, 2015 Sold. That would make things a lot simpler. Quote Link to comment Share on other sites More sharing options...
zilverbullet77 Posted May 26, 2015 Share Posted May 26, 2015 Can't tell if serious I suppose after all the rust repair is done, engine and suspension back in, hopefully it would be many years before removing it again. I am glad you asked, I wasn't sure either! Quote Link to comment Share on other sites More sharing options...
TUME Posted May 27, 2015 Share Posted May 27, 2015 I did new frame rails from 60mm wide tubing and just drilled new mounting holes to rails and crossmember. Quote Link to comment Share on other sites More sharing options...
2jztank Posted May 29, 2015 Share Posted May 29, 2015 Can you guys show some pics of this please... Quote Link to comment Share on other sites More sharing options...
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