advice on my first real project

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hi, so i have a BBQ smoker project for spring but this came up now. they are downpipes for my buddies car and he wants me to remove the resonators because one if them has a bad rattle inside. i'm planning on cutting them out and replacing it with a pipe. my question is how do i build a jig for it so that it doesn't move while i'm doing the work on a bench? i thought about welding some 1x1 square that i have laying around from one flange to the other, would this be enough?also, i know someones gonna say its stainless and how do i plan on welding it i'll take care of that now. i'm just going to replace it with pipe from another exhaust, its also SS but not the same grade as this, it doesn't have to be pretty because i'm going to grind the welds (if they're that ugly) and hit it with some VHT paint.thank you Attached Images
Reply:I would tack it back together on the car if it was me, then remove it for finish welding.  That greatly reduces your chances of messing up.
Reply:haha, i knew i forgot something. the car is 400 miles away in LA and even if i did have it, its in a pretty difficult place to get to. at least the top side, not so much on the bottom one,thanks for the quick reply.
Reply:Make a fixture.  Take some flat scrap pieces and drill a couple holes so the exh flanges can be bolted to them and tack weld them to a longer piece while bolted to your resonator section - this will simulate the remainder of the exhaust system.- "If ya can't be handsome, ya may as well be handy!"   HTP Invertig 201Lincoln Power Mig 255CLincoln SP125+Thermal Dynamics Cutmaster 38
Reply:Are you sure those are resonators?  I had a similar set up on my mustang.  Turns out they were actually catalytic converters.  It had two right by the exit from the factory headers on each side of the car, and two more catalytic converters further down the exhaust underneath the car.  System developed a rattle at low RPM's.  I disconnected my exhaust system and looked inside the converters/resonators whatever they were by the exhaust headers and could see a honeycomb ceramic plate or filter of some sort that the exhaust gasses would normally flow through.  I could see one of them was broken and was loose.  Took a hammer and a 1/2" diameter steel rod and broke it up into little pieces to get it out.  Did it on both of the converters by the headers.  No more rattle.  Also changed the exhaust sound.  A little louder and deeper sound.  Didn't affect emissions testing either.  Car still passed with flying colors.
Reply:Originally Posted by eaw99517... I disconnected my exhaust system and looked inside the converters/resonators whatever they were by the exhaust headers and could see a honeycomb ceramic plate or filter of some sort that the exhaust gasses would normally flow through.  I could see one of them was broken and was loose.  Took a hammer and a 1/2" diameter steel rod and broke it up into little pieces to get it out.  Did it on both of the converters by the headers....
Reply:Originally Posted by eaw99517Are you sure those are resonators?  I had a similar set up on my mustang.  Turns out they were actually catalytic converters.
Reply:i'm sure they are resonators. and i wouldn't worry about telling people you have gutted cats unless you live in nazifornia like i do. thanks for the replies guys.
Reply:Resonators don't usually have A.I.R. tubes dumping directly in front of them, nor do they usually have data plates tacked to their sides.  They are also usually in the main exhaust stream, not before the cats.  But if you say they're resonators, OK.  What kind of car is this?  As far as not worrying about telling people you've done the dirty deed....  Gutted cats will get you the $10,000 fine wherever you live.  I know a couple of guys that live back in the sticks near me that got hit by the fine.  We don't even have emissions inspection here.  It's a Federal law and the fine is a Federal fine.  Your state fines, whatever they may be, are in addition to it.  Loose lips sink ships - that's how these guys got busted.  Some people who didn't like them heard the rumors and passed them on to the right people.  Just trying to make sure you know the way it works.  I know the guy who does the work gets the fine, and "I didn't know it was a catalytic converter, I thought it was a resonator" won't get you off.  Just be sure you know what you're getting into if you're wrong or if you're being lied to.
Reply:thank for your concern. those are not air tubes they're for the A/F ratio sensors and this is going on a 06 G35.i've been in the "import scene" for over 10 years now and was a toyota certified tech for 9 so i know every CA law that would affect me, thats why all of these parts are for OFF ROAD USE ONLY  and that tag has the manuf. logo on it, not a data plate. also in ca, all aftermarket cats are illegal unless they have a CARB number, which only a hand full of manuf. have.Last edited by superwelder; 01-23-2012 at 09:17 PM.
Reply:3 things:- Those are the smallest flex pipes I have ever seen.. 1" long?- The doubled up spark plug non-foulers fool obd2 trick are a pretty good indication that the cats are already removed...- a shortcut I have used is if you have enough good clamps, clamp wach flange to a piece of scrap, then weld the scrap to your work surface. Then cut the bad part out, weld the good part in, unclamp it, grind the welds off on the scrap you tacked to the table for your temporary work jig.miller syncrowave 250hobart handler 140home made 400 amp engine driven in progress...
Reply:thanks, i really don't have a good bench to work on (another project for spring). all i have right now is the floor and a wood bench.those flex sections are short but its better than nothing i guess and good observation on the anti foulers.
Reply:In the absence of a steel workbench, try a long-enough piece of channel iron as a base for your jigs.You're safe since you're working on a set of test pipes and not the factory originals which did have converters in that location - I didn't catch that.
Reply:thanks, i'll have to find some.i've actually been looking for any scrap metal that i can get to play with but its impossible on craigslist because so many people are picking it all up to recycle and make money on. i would like to find a good steel plate to make a table out of, most likely i will be getting all the other material at my local metal supplier. anywhere else i can go to find metal?
Reply:You might check with the metal recyclers themselves.  There is one located close to where I live and they have an area set aside for some of the stuff like steel plate, I-beams, tubing, etc for you to go through.  They call it "Project Paradise".  They charge ¢30 a pound.  Picked up some pretty good stuff there.  They usually have loads dropped of on Thursdays so that's when I go down there.  Only drawback is that some of it has some rust on it that has to be ground off if you're going to weld.
Reply:Why not just cut the top open, take out what's rattling and weld the top back on. It would have the appearance of being stock to the untrained eye that way.No need for a jig either.
Reply:thanks, i'll check with the recyclers around me.there is no way this pipe will pass for stock thats why i'm not worried about appearance, also a straight piece of pipe will flow better. aaaannnndddd i just want to do some cutting and welding
Reply:They look like cats to me too.  I've damaged a few in my day and once the material comes loose of the metal, it rattles like crazy.www.lindgrensupercars.comMiller Dynasty 350Miller Dynasty 200DX - retiredMiller Millermatic 210Miller Spectrum 3080Miller "Power of Blue" stool  Miller Syncrowave 180SD - retired