Zoldman Posted October 28, 2003 Share Posted October 28, 2003 OK, how bout this? I have a '73 240. I'm going to put a stock '94-'96 Corvette LT1 (300hp/330ftlbs) with an L460e auto trans in her. No real racing, just some spirited driving and blowing away a few of the snotty rich kids in my area that like to laugh at old cars.(they already hate my '79 Vette) What kind of bracing will be needed, and can I do enough without welding something up? I can do most everything else, but welding is not in my arsenal. Are tower braces enough? This is an area that I am weak in, and sure could use some help. I will take it to someone to get the bracing done right if that's what it takes. What do the experts think? Thanks Bill Quote Link to comment Share on other sites More sharing options...
PETEW Posted October 28, 2003 Share Posted October 28, 2003 Hey guys, I have a '77 280 with a stress crack on the passenger b pillar (car came with it). I plan on putting in sub frame connectors and I have an Autopower 4 point rollbar. My question is this. If there are cracks in the pillar allready does that mean the frame is twisted, or is this just a warning sign that bad things will happen if it isn't strengthened. I'd hate to put all these things in only to find that the frame is tweaked. Thanks. Quote Link to comment Share on other sites More sharing options...
Michael Posted October 28, 2003 Share Posted October 28, 2003 Welding the roll bar to the map light area of the "roof" (or more precisely, the sheet metal enclosure that houses the hatch hinge mounting points) is an excellent idea. The roll bar in my 280Z's cage is welded to this sheet metal enclosure in two places, one just behind the driver's head, and the other behind the passenger's head. It's also a good idea to weld the roll bar to the points (passenger side and driver side) on the unibody sheet metal near the front bottom corner of the quarter-windows. That turns the roll bar into a sort of B-pillar. This approach is useful, in my opinion, regardless of whether you go with a full cage or limit yourself to a roll bar and strut tower braces. In either case, the theme is: tie the tubing into the unibody wherever possible. Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted October 28, 2003 Share Posted October 28, 2003 My low 12 second 1/4 miler is beginning to show cracks around the passenger side rear pillar. It's a 1971 240Z with a roll bar and rear strut tower brace. Mike Quote Link to comment Share on other sites More sharing options...
Phantom Posted October 28, 2003 Author Share Posted October 28, 2003 That's where mine is too. I ordered an SCCA spec roll bar today. I'm going to get it in and then look at beefing up the frame rails. we'll see after that. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted October 29, 2003 Share Posted October 29, 2003 Becareful when you guys talk about triangulating braces. I was at the MSA show this year, and 99% of the roll cages/bars etc.. were not installed in the optimum position. When you triangulate the front bars, and you do not have a full cage that passes through the firewall, ie with caging under the dash.. ie only running strut bars.. Most bars I have seen installed were placed incorrectly. Most were mounted in/on, around the hood latch area.... WRONG... if you remove the cowl panel, you'll see that your windshield wipers are mounted on the other side, and that it is only sheet metal...ok If you look outboard about 12 inches each way, you will see a brace from the firewall backwards towards the windshield...This is where you should mount them... much stronger than the back side of the wipermotors. place some thin steel plate in that area to distribute the load, and weld on your flange to it. I noticed a difference when I ran my car on the track with and with out the strut bars, and noticed a further difference as I learned to push the car harder, when i had the roll cage installed.. no more squeaks and rattles going over rail tracks etc... On a side note, I've said this before, the front rad support is EXTREMELY important. For any who have chopped into it to pass i/c pipes through.. consider bracing this area again. even with my 12 point roll cage, when we cut that support out for access reasons when installing my engine swap, the front end could flex more than 1/2 inch depending whether the car was on the ground or on the hoist!!!! The piece we cut out, either would not fit (car on ground) or had almost 1/2 inch of play..(when car was sitting on hoist) This was with the engine/driveline OUT!!!! Just some food for thought.. I love my cage...who cares that it added some weight... Quote Link to comment Share on other sites More sharing options...
Guest Perry Posted October 29, 2003 Share Posted October 29, 2003 Be careful with using the paint cracks as an indicator of chassis problems. my 280 cracked there after my turbo install and when I got all the lead off I discovered the steel was rusted through from inside out. I wish I had gone at it from inside and welded a piece of sheet metal over it without messing with the lead. I have since done 2x3 subframe connectors and notice the doors don't stick anymore when I have one corner jacked up. I also plan a roll bar tied to the strut towers, roof, and lower B pillar area. and a "monte carlo" bar, although I haven't decided where to mount tot he firewall yet as none of it looks real solid to me. maybe I'll weld a 1 inch square tube all the way across the top of the firewall then attach to that. also keep in mind that if you tie to the firewall right in front of the dash outboard of center a hard front impact may impail you with the tie in bar, this is a common problem in homebuilt aircraft. Perry Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 29, 2003 Share Posted October 29, 2003 Perry, if you're talking about being impaled by the strut tower bar, I think there would be other things to worry about before that. The length of my bars that go to the firewall are maybe 2' long, and they are tied into the area that ZR8ED mentioned, where there is a support underneath the cowl. For that to bar to impale the driver, it would have to move probably 4' or 5', and either come through the dash or follow it. You're already dead in that case!!! Jon Quote Link to comment Share on other sites More sharing options...
zguy95135 Posted October 29, 2003 Share Posted October 29, 2003 ZR8ED you were talking about roll bars not being installed right. i got mine a few weeks ago and when i installed it i pushed it as far back as it would go and i can barely get a finger between the bar and the roof. http://www.hybridz.org/phpBB2/album_pic.php?pic_id=2008 is it in the right place? Quote Link to comment Share on other sites More sharing options...
Mikelly Posted October 29, 2003 Share Posted October 29, 2003 YOu need re-enforcement...Period. This is an accumulated effect issue... You really want to ensure that the car stays as straight as it currently is. YOU WILL Damage the unibody... It is just a matter of when, not If. Mike Quote Link to comment Share on other sites More sharing options...
Guest Perry Posted October 30, 2003 Share Posted October 30, 2003 jmortenson, yea I agree it's a long shot. i more wanted to make people aware of that sort of issue. I've seen a few cars and quite a few airplanes with tubes that stand a good chance of impailing the driver/pilot in a hard impact. It's common in airplanes to put a support at the top of the panel which is aimed right at your head in a front impact. Probably not an issue in most Z cars, just remember to think safety everyone. Perry Quote Link to comment Share on other sites More sharing options...
johnc Posted October 30, 2003 Share Posted October 30, 2003 Most bars I have seen installed were placed incorrectly. Most were mounted in/on, around the hood latch area.... WRONG... Aaahhh Grasshoppah. Things not always as seem. If you did a section through that area you would see that the cowl is shaped like a triangle with one side being the firewall/hood latch. If you build a mount that spans this base and ties into the other two side of the triangle you end up with a very strong mount. Most people don't notice the line of spot welds on the firewall about 4" down from the top lip. Once you have a strong mount in the center, the forward braces are at a much better angle to counter any fore/aft and twisting of the strut towers. Check out the firewall mount from my car: http://www.hybridz.org/phpBB2/viewtopic.php?t=7326 Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted October 30, 2003 Share Posted October 30, 2003 "spans this base" is the key word here. Most just use a piece of plate steel, or worse, mount a flange directly to the firewall... If you are going for the "welding a plate to the firewall for mounting a flange to, mounting it further outboard near that extra bracing is still better than just the sheet metal of the firewall in which the wiper motor is mounted to.. Try and flex that section with the wiper motor removed...it is not very strong at all on its own.... If you build a mount that spans this base and ties into the other two side of the triangle you end up with a very strong mount. You are certainly correct with that statement. I'm not looking at the point of the correct way of building a roll cage, as in that case, the triangulating part of the tower braces is actualy inside the car, and proper building plans for roll cages has long ago been professionally worked out. I'm commenting on the simple installation of two braces for the strut towers, and if your not going for the full cage, you may as well install them properly to work on their own. This also happens to be an excellent fix for those of us that have set back engines that don't allow to even have the hood latch mech. I still stand by my statement that most of the cages and braces I saw at the MSA show, were not installed very well... and I won't even get into the whole "bolt in cage" stuff... ya either need it or don't.. Quote Link to comment Share on other sites More sharing options...
Phantom Posted November 3, 2003 Author Share Posted November 3, 2003 Well - the Top End Racing front strut bar I installed bolts to the firewall about 8" either side of the hood latch and seems really solid. The rear bar bolts to the top of the towers both sides and then 'V's' back across and down to bolt into the drivers side a second time down low. I also installed the Auto Power SCCA rated roll bar over the weekend so the back end should be getting pretty rigid now. I still plan on reinforcing the sub-frame connectors but that is a ways out. I've got other fish to fry on this car before I get back to that. Quote Link to comment Share on other sites More sharing options...
rc's240z Posted November 3, 2003 Share Posted November 3, 2003 All good ideas, I have seen Johns car and know the time and research that he has put into his car... We have found that for a "bolt in application" that our strut bar solution makes a huge difference in handling, by supporting the strut towers from twisting, adding a subframe connector to front sway bar mount, and cross bar to tie the strut towers together see attached link "A" below. You will notice that we use two supported pickup points on the firewall so that you can push your motor back as far as possible for say a V8 conversion, and that our bar ties into supported sections of the firewall for better rigidity. Link "A" : http://www.pdkfabrication.bravepages.com/240%20front.htm A step beyond this is a welded installation. That effectvely would allow you to do the same thing see link "B": Link "B" : http://www.classiczcars.com/photopost/showphoto.php?photo=7456&password=&sort=2&thecat=500 I will appologize in advance for the popups on Link "A", please feel free to examine my other photos on link "B" Quote Link to comment Share on other sites More sharing options...
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