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Stitch/Seam welding. Any cons?

Old 06-07-05, 12:49 AM
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Stitch/Seam welding. Any cons?

I'm rebuilding my FD and have it stipped down to the chassis at the moment. I figure this would be a good time to seam weld it, but was wondering if there would be any possible negative effects from doing this. I know it should be done with the car sitting on the suspension and not in the air. This will be primarily a street car with potential track use for now, but hope to use it as a track-only car in the future. Let me know what you think. Thanks
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Old 06-07-05, 01:44 AM
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Too much time and money will go into this process. and my opion it is not need for a street car or some weekend track car.



my opion. got a good weld in roll cage. that will improve chassic alot for your goal.
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Old 06-07-05, 08:33 AM
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I don't know if these cars are dipped for putting primer on them but you will burn stuff off in places you can't get to and start the rusting process in weird places. Have you thought about 2 part foam in the rocker panels and frame rails instead?
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Old 06-07-05, 09:23 AM
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Let me tell you a couple more things. The entire car is bare metal now with all the seam sealer stripped off. It will be getting new primer, paint, seam sealer, and rust inhibitor where I can't get paint. I have the time, skill, and the equipment. No more money required.

A full cage, in my opinion, is not safe on a street car.

What do you say now?
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Old 06-07-05, 09:25 AM
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As for the urethane foam, I've yet to find someone who had done it to an FD and can vouch for it being worth the weight and money. The frame rail on the FD is huge, and to get that stuff to be affective, you would want the higher density foams.
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Old 06-07-05, 11:24 AM
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Well then go for it. To me it sounds like the only downside will be the slight increase in weight from the filler rod (negligible).
Good luck
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Old 06-07-05, 01:57 PM
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If you can get to all sides of the areas you weld, go for it. That would be my only concern. I've drilled holes and squirted OSPHO in to them then hit the hole with compressed air to spread it around. That worked pretty well on my old FIAT, and that company perfected rust. As for the foam, you can get different weights. Anywhere from 2 lbs per cu.ft. to over 8lbs. per cu.ft. A cubic foot is a lot of volume and the 2 lb stuff gets hard enough. All you're trying to do is control any small amount of flex that may occur in the steel tube of thin metal. While the rockers may be OK, rails up front on either side of the engine can use help. Infiniti does the rockers at the factory on one model,if not all, of their cars. Check out http://fgci.com and look in the catalog for foams.
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Old 06-07-05, 02:02 PM
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have you seam welded a car before?

density doesn't play a huge roll in structural foams. You don't need high density to get high strength.
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Old 06-07-05, 02:15 PM
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All Professional Rally and Production based cars seem weld (Stitch weld, not complete weld) the entire chassis before cage is installed. You gain substantial strength by doing so. The only draw back is repairing the chassis in a wreck, Takes a bit longer.

And also, if you decide to track the car in a Sanctioned event (SCCA, NASA) you will need to check the rules for the class you want to run it. Most IT classes do not allow seem welding. May cause problems in the future.
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Old 06-07-05, 05:35 PM
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Last I checked, the FD's weren't classed in IT other than ITE which is pretty much a free for all here in the midwest.

Like Russ said, just be aware that seam welding is not welding the entire seam... it's stitch welding.

If you can live with the increased rigidity on the street, then go for it. You're at the perfect time to do it with the car in it's current state.

Toss in a roll BAR and you'll be rattling your fillings out before you know it
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Old 06-07-05, 08:39 PM
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On the foam--So the urethane foam is just to keep the structure of the frame rail from flexing around? So the foam in itself is not acting as an additional "rail"? I was thinking of it a little backward I think.
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Old 06-07-05, 08:45 PM
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The car will have an LS1, so I'm not sure if that affects the class it races in. I don't want to do something that will keep me out of anyting in the future. Stich welding the whole car isn't something I can really reverse.

And no, I haven't seam welded a car before.
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Old 06-07-05, 08:50 PM
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And does anyone have some photos of seam welds to post? How long should the welds be and how frequently should they be placed along the seams?
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Old 06-07-05, 09:31 PM
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Just do a search for Rally Cages and seam weld. There should be plenty of pics on the web for you to look at.

Personally, about 1-1.5" long and about the same space apart when you can. Skip around the car so you don't get one area too hot. Once you get into a rythim it starts going pretty quick.

Make yourself some sort of pattern with your spacing marked so that you can stay even and you wont have to flip your hood as often.

Autodark hood is a must. Use a dental pic/scraper to clean out the seams before beginning. That'll make welding it a little more enjoyable.
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Old 06-07-05, 11:18 PM
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I seam welded my FC. I did 1" to 1.5" welds about every 3" on the major seams. I did half the weld and then moved on to avoid heat build up. I then came back and finished up the other half. Took me three long days and about a roll and a half of wire (12 lbs rolls). So I figured I added about 16 lbs to the weight of the car, but most of it down low, where most of the welds are. Take your time, ensure the seam sealer is completely removed and ensure the surface is very clean. I dipped my car and some seam sealer still remained. A wire brush on the end of a die grinder works wonders

-Trent
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Old 06-08-05, 04:21 PM
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Originally Posted by Speed Raycer
Last I checked, the FD's weren't classed in IT other than ITE which is pretty much a free for all here in the midwest.

Like Russ said, just be aware that seam welding is not welding the entire seam... it's stitch welding.

If you can live with the increased rigidity on the street, then go for it. You're at the perfect time to do it with the car in it's current state.

Toss in a roll BAR and you'll be rattling your fillings out before you know it
if i ever got the chance to do stich weld the entire car with a tig welder I would not even think twice.

BTW I thought it was the 400 lb/inch springs that causes your fillings to rattle loose. Good thing I don't ahve any fillings
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Old 06-08-05, 05:31 PM
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The structural foam I know thats designed for cars is itw foamseal. Do a net search, they have a website. That is the CORRECT stuff for a this application.

PS- You level of modding will knock you out of most sanctioned racing I know of. Maybe you can be fit into some free for all class. If this is going to be a racecar I suggest you figure out what class you want to run in and engineer your car from that perspective, keeping the RULEBOOK close at hand.
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Old 06-08-05, 08:37 PM
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I'm mostly interested in Autocross, I think. I haven't ever had my car going well enough to try it out though. Are there any classes in that in which I could compete competitively? I'll see if I can find some rules on that. Most likely it looks like this car will remain a street rod/weekend warrior. I would like to be able to compete in something on a competitive level though. Seems silly to have a car of this caliber and not be able to use it to its potential.
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Old 06-09-05, 02:55 AM
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I've heard that stitch welding can warp the chassis if you don't work in the correct pattern. You might want to consult someone who's done this before. The rally crowd does it, almost out of necessity. They should be a good source for information. Here's a few links I found from Google:

http://www.fourstarmotorsports.com/C...Welding_45.htm
http://www.bmsc.com.au/forums/archiv...hp/t-1218.html

-s-
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Old 06-09-05, 04:59 AM
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can you post pics of your bare chassis FD? wouldnt mind seeing that
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Old 06-09-05, 09:13 AM
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Its a sad sight.... I don't think you can handle it.
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Old 06-09-05, 09:37 AM
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This company use to market a two part foam specifically for automotive applications. But, their site doesn't show it anymore. Wouldn't hurt to call them as they may still have it.

http://www.itwfoamseal.com/auto_aftermarket.htm
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Old 06-09-05, 09:57 AM
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Before you do anything, check the rules where you intend to compete. And then usually the best money you can spend to make a car faster is to send the nut that holds the steering wheel to a drivers school.
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Old 06-09-05, 12:10 PM
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Give Jerry Kelso a call about your legality of your power plant and to determine if there is a class you can run in for Road Race. Jerry is our head Oregon Region SCCA tech, his number is 503-682-2410.

Drag racing will be no problem as long as you follow the rules for their cage. Anything goes. SCCA and Conference has changed a couple of years back. Most open classes have changed the rules for powerplants, same as car!

I wanted to put a SBC in a Sec Gen and run ITE, but they reworded the Region's

Rules: Engine modifications are limited to the ITCS preparation rules (ITCS 17.1.4.D.1-3) except for the following:Cars may use an alternate engine block. The engine block must be from the same manufacturer as the chassis. The engine must remain in the original location utilizing the factory engine mount locations. The engine block type (example: V8) must remain the same as originally delivered and/or offered for sale from the manufacturer.
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Old 06-09-05, 06:14 PM
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Hell, if I can't race against other people, whats the point of seam welding the car? I'll just put in a roll bar so I can drag it once and a while and be done with it, I guess.
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