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WagonCrazy
12-10-2017, 10:57 AM
As I approach the purchase of the exhaust components for my Nomad build, I'm faced with a choice of materials to do this in (mild steel, aluminized steel or stainless steel).
And I'm faced with a limitation of only owning a MIG welder.
And I want to fabricate it myself, using mandrel bent pieces that I can get online.

So the main question here is "can I spot weld stainless components together with my MIG welder, then remove the system from under the Nomad and take the pieces to someone for complete Tig welding?
Does it screw anything up to fabricate it all under the car first, by carefully spot Mig welding each piece as needed to be satisfied with the whole system layout, and then dissasemble/remove it all and take it to a buddy for Tig welding "on his bench"?

Some aspects of this exhaust build I've got sorted out, like going with a quieter muffler like Flowmaster 50 or Magnaflow 3xl. Both are 3 chamber style mufflers, much quieter in interior drone than the equivalent 2 chamber mufflers that have been so popular over the years with builders. Both seem to be made in either stainless or mild steel. And I'm OK with sacrificing a little HP with these quieter mufflers for more enjoyable cruising.

Deciding between going with 2.5 inch or 3 inch diameter system also. I'm only running a bone stock 340 horse LS1 engine/T56 trans, and don't plan to ever have more than 500 horsepower in this thing.

Let's start here. Give your opinion on exhaust materials and the welding question above.

55 Rescue Dog
12-10-2017, 11:19 AM
I tack weld stainless all the time with a MIG with steel wire using 75/25 gas. Tried stainless wire which works, but spatters more. It can rust a bit with steel wire.
806780688069

chevynut
12-10-2017, 12:20 PM
I don’t see anything wrong with tacking with mig. I personally would use stainless wire that’s recommend for the type of stainless you’re using. You could even weld the whole thing but tig gives much nicer welds. I back-purged my tailpipes and the welds turned out much nicer inside.

Rick_L
12-10-2017, 05:26 PM
You can tack weld stainless just fine with a mig welder and carbon steel wire. Thing is, the welds will rust eventually, actually sooner than later on an exhaust system. The hard way to prevent this would be to tack weld everything again with tig and SS filler wire, then grind the mig tacks to removed the carbon steel filler. You probably will still have a contaminated weld though.

Why not try to find a spool of stainless mig wire for your mig welder and try it? I think what you want is 309 alloy stainless, at least that's the filler I use for tig with 304 and 321 stainless. The cost of a small roll won't be much. What I don't know is how your typical 75/25 mig gas for carbon steel will act.

If you're not going to have stainless mufflers (you mentioned Flowmasters) - why not go with steel tubing too? You can probably do it with steel and ceramic coat it for about the same cost or lower than stainless. Something to consider if you haven't bought tubing yet. That's the way I'm going - the headers and fabricated tubing will be carbon steel, ceramic coated - but I'll just leave the mufflers aluminized, and use high heat paint on the flanges I weld to the mufflers.

NickP
12-10-2017, 07:23 PM
I'd see if you could rent/purchase a small bottle of 100%. My last experience with MIG and Stainless with 308lSi (AKA 308LSE2) or (ER-308l [Hobart]) and 100% worked pretty well.

WagonCrazy
12-10-2017, 07:28 PM
All good advice guys. Thank you.

I back-purged my tailpipes and the welds turned out much nicer inside.
Laszlo, explain this process more to me please

NickP
12-10-2017, 07:42 PM
Pretty simple. You simply fill the innards of what you are welding using a plug at both ends, a regulator to feed argon (100%) into the chamber and proceed to TIG as usual. Be prepared to spend some bucks on gas.

http://www.millerwelds.com/resources/communities/mboard/forum/welding-discussions/11339-cheapest-way-to-back-purge-with-single-tank-of-argon

WagonCrazy
12-10-2017, 08:27 PM
If you're not going to have stainless mufflers (you mentioned Flowmasters) - why not go with steel tubing too? You can probably do it with steel and ceramic coat it for about the same cost or lower than stainless. Something to consider if you haven't bought tubing yet.

Seriously thinking about going in this direction Rick. The hooker long tube headers are just mild steel, so why bother with the rest of the system being stainless? I'm really not sure what the cost of ceramic coating for an entire dual system is, but geez...I've spent so much to date that I've just stopped adding up receipts.

So If I go with mild steel all the way (including the mufflers), then I CAN weld it up with my Mig and call it a day. I also found out that i can get VBand clamps in mild steel also (well Im guessing the weld on bands are mild steel and the outer clamp ring is stainless...so that works), so I can weld up this system entirely after I fabricate and tack it up.

Rick_L
12-11-2017, 05:28 AM
Most of the V band clamp flanges are stainless also but you can weld them to carbon steel with whatever technique/filler material you like. Just coat or paint when complete.

MP&C
12-11-2017, 06:05 AM
We welded up mandrel bends (flowmaster kit) and Flowmasters, using stainless v-bands and MIG. Then owner powder coated using high-heat powder coat. Close match to the Jet hot of the headers. Not exact, but close..

chevynut
12-11-2017, 08:02 AM
Steel WILL rust inside......stainless is forever. If the cost is the same why go with mild steel? IMO there’s no benefit. Combustion generates a lot of water. Headers run hotter than tailpipes. I didn’t think twice about going with stainless.

NickP
12-11-2017, 09:10 AM
Steel WILL rust inside......stainless is forever. If the cost is the same why go with mild steel? IMO there’s no benefit. Combustion generates a lot of water. Headers run hotter than tailpipes. I didn’t think twice about going with stainless.

For the most part, I would agree that stainless would be the better choice especially if the price is the same. If price is not, give thought to the purpose of the car. Will it just be a weekend car? Will it be a daily driver or highway cruiser? If so, then longevity would garner thoughts of stainless versus carbon steel even aluminized or coated. Unless it's coated inside and out, rust (carbon steel) will begin its job of destruction.

Custer55
12-11-2017, 03:14 PM
I Mig welded mine with steel pipes and stainless Magnaflow mufflers. I painted all the pipes with POR high heat exhaust paint which has held up very well with 2 seasons of driving on it. My headers are Sanderson block huggers with ceramic coating and the pipes connected directly to the headers show no signs of any paint failure.
Brian

BamaNomad
12-11-2017, 07:32 PM
ONE more opinion of stainless: Stainless pipes are generally thinner metal than the steel ones, and much thinner than aluminized, and that 'lack of mass' comes thru in a 'tinny SOUND', which I personally do not care for... and that is why I'd use anything OTHER than stainless..

NickP
12-11-2017, 08:20 PM
In all of the units we built, we kept the proper gauge/wall thickness but to note, we never buy kits in a can.

chevynut
12-11-2017, 09:04 PM
Stainless pipes are generally thinner metal than the steel ones, and much thinner than aluminized,

That is simply not true. My exhaust pipes are 16 gauge stainless which is at least as thick as any commonly used mild steel exhaust pipes. Sure you can buy thinner material but 16 gauge is common. And it STAYS that thickness because it doesn’t rust. Most exhaust systems on newer cars are stainless.

BamaNomad
12-12-2017, 07:11 AM
That is simply not true. My exhaust pipes are 16 gauge stainless which is at least as thick as any commonly used mild steel exhaust pipes. Sure you can buy thinner material but 16 gauge is common. And it STAYS that thickness because it doesn’t rust. Most exhaust systems on newer cars are stainless.

CN? Who sells stainless exhaust systems for older cars made of 16 gauge or thicker? I know you can purchase your own SS in whatever thickness you want and roll your own, but my comment was related to the 'off the shelf' SS systems sold for 'restoration purposes' for classic chevys and other cars, corvettes, etc from the fifties/sixties/seventies... and they sound like CRAP... but that's just one man's opinion, and we all have one.

NickP
12-12-2017, 08:00 AM
CN? Who sells stainless exhaust systems for older cars made of 16 gauge or thicker? I know you can purchase your own SS in whatever thickness you want and roll your own, but my comment was related to the 'off the shelf' SS systems sold for 'restoration purposes' for classic chevys and other cars, corvettes, etc from the fifties/sixties/seventies... and they sound like CRAP... but that's just one man's opinion, and we all have one.

What's the advertised gauge of the items you're mentioning and who is the supplier? If it's thinner than advertised and you (not you personally) purchased it, shame on the buyer for not reporting it and shame on the supplier.

BamaNomad
12-12-2017, 08:25 AM
What's the advertised gauge of the items you're mentioning and who is the supplier? If it's thinner than advertised and you (not you personally) purchased it, shame on the buyer for not reporting it and shame on the supplier.

My *experience* listening to restored cars with stainless exhaust goes back to the 80's and 90's when cars were being *restored* to original for show purposes... about the only times you heard them running was when they came in/out of the trailers and driven onto the show field. At that time, most of the restoration suppliers for exhaust systems had SS options, but I don't recall EVER seeing the gauge of the metal mentioned; nor do I recall ever seeing what the gauge of the original metal in the exhaust systems were.. I've had a 'negative' attitude re SS exhausts since that time; I do not like the tinny sound associated with those exhausts. I don't like the stainless aftermarket exhaust for C4/C5 Corvettes either, for the same reason... (I have a friend who said one time, as we listened to a C4 corvette with the new at the time Corsa exhaust) that it 'sounds like a fat man farting into a tin can!'... :)

If/When I heard an OTS stainless *restoration* exhaust (which doesn't sound tinny, I'll re-adjust my attitude appropriately...

chevynut
12-12-2017, 09:12 AM
I thought wagoncrazy was posting to get feedback on a custom exhaust system made of stainless mandrel bends and straight stainless pipe. Nobody said anything about an OTS stainless exhaust system. They can be made out of whatever the manufacturer wants to use and you can choose NOT to buy thin ones if you don’t like them. Same with mild steel. I think mild steel exhaust pipes are often 18 gauge as are a lot of headers. To claim that stainless exhaust systems are inherently “thinner “ material is false.

chevynut
12-12-2017, 09:18 AM
The “tinny” sound you don’t like is probably more from the headers and mufflers than the tailpipes and most headers are mild steel. Most new cars use stainless exhaust systems and you can barely hear the exhaust at all.

chevynut
12-12-2017, 10:28 AM
http://pypesexhaust.com/i-12200930-55-57-chevy-2-5-crossmember-back-w-x-change-sgc11.html

"409 stainless steel.

Pypes Exhaust Systems are designed to deliver enhanced performance, provide extra punch in the passing lane and improve gas mileage. Fabricated using the highest quality materials, our smooth, 16 gauge, mandrel-bent, Stainless steel pipe ensures maximum exhaust gas flow, which can significantly boost horsepower. The stainless steel construction of our pipes and mufflers enables them to resist corrosion and extends the life of the system."

chevynut
12-14-2017, 09:02 AM
Pretty simple. You simply fill the innards of what you are welding using a plug at both ends, a regulator to feed argon (100%) into the chamber and proceed to TIG as usual. Be prepared to spend some bucks on gas.

http://www.millerwelds.com/resources/communities/mboard/forum/welding-discussions/11339-cheapest-way-to-back-purge-with-single-tank-of-argon

I put as tee on my regulator with a small valve on it and connected a 1/4" nylon hose to that. I didn't use a second regulator. I plugged both ends with some foam pipe insulation leaving a small hole in the center on each end. Then I inserted my hose in one end and turned on the gas a little. You don't really need to flow much gas, all you really have to do is displace the air. I didn't use much gas as far as I could tell on my gauge. Ideally you'd have a flowmeter on the line but I just guessed.

NickP
12-14-2017, 09:06 AM
There is a Y kit available or simply rent or use your backup bottle and a regulator.

chevynut
12-14-2017, 07:46 PM
Who needs a "kit" for this? You can get the parts at Home Depot.

NickP
12-15-2017, 07:13 AM
Who needs a "kit" for this? You can get the parts at Home Depot.

Just providing and alternative to those that might want something different but, it's all good.

Bitchin'57
12-15-2017, 08:04 AM
You can tack weld stainless just fine with a mig welder and carbon steel wire. Thing is, the welds will rust eventually, actually sooner than later on an exhaust system. The hard way to prevent this would be to tack weld everything again with tig and SS filler wire, then grind the mig tacks to removed the carbon steel filler. You probably will still have a contaminated weld though.

Why not try to find a spool of stainless mig wire for your mig welder and try it? I think what you want is 309 alloy stainless, at least that's the filler I use for tig with 304 and 321 stainless. The cost of a small roll won't be much. What I don't know is how your typical 75/25 mig gas for carbon steel will act.

If you're not going to have stainless mufflers (you mentioned Flowmasters) - why not go with steel tubing too? You can probably do it with steel and ceramic coat it for about the same cost or lower than stainless. Something to consider if you haven't bought tubing yet. That's the way I'm going - the headers and fabricated tubing will be carbon steel, ceramic coated - but I'll just leave the mufflers aluminized, and use high heat paint on the flanges I weld to the mufflers.
Rick, I tried MIG welding stainless wire with 75/25, and the weld comes out black, and like 55 Rescue Dog said, it spatters more.

WagonCrazy
12-15-2017, 09:12 AM
So to recap a few things I've learned from you guys on this topic:

It's possible to weld stainless pipe/bends/mufflers/vbands/exhaust tips with my Mig welder and existing steel wire, but the welds themselves will eventually rust (if not coated, painted, jet hotted, etc).

It's possible to do same as above, but use stainless wire with my Mig welder, and that will require a bottle of 100% argon. 2# spool of stainless wire is about $25 and the small bottle about $100. But the headers are mild steel, so I still need to deal with a jet hot coating process for those.

2 1/2 inch diameter is going to be fine for this system, based on 340 hp LS1 engine and long tube headers. 3 inch is not necessary.

Magnaflow mufflers are ONLY stainless steel.
Flowmasters are ONLY steel.
Borla's are ONLY stainless steel.
Choices...seems like a mix and match thing going on here.

So I have mild steel headers to start with. Thinking about just fabricating the rest of the system in mild steel (except the mufflers in stainless since they can't be adequately coated on the insides), and Mig welding it all myself, then having all pieces jet hot coated (except the mufflers). I may even just hide the tips up under the bumper extensions (left and right) like I did on my 9 passenger wagon build. That way, there's no need for stainless tips because you really don't see them.

Choices, choices...

chevynut
12-15-2017, 09:30 AM
Paul, have you priced stainless bends and tubing, as well as Jet Hot coating everything? My headers are mild steel (Earle Williams') but everything else including the mufflers is stainless. I bought the stainless parts on eBay and from Burns Stainless. I have a sheetload of 3" stainless tubing that I didn't use and don't even know why I bought so much....also have a lot of 2" because I was going to build headers but realized j-bends would have been better for that. Not sure what I'm going to do with all that stuff.:?

My exhaust system cost about $2500 so far including headers, bends, tubing, expansion joints, v-band clamps, flanges, DMH electric cutouts, hangers, and mufflers. I still have around $300 in header coating costs so it's pushing $3000 but it's 3.5" and 3" stuff.

If I were you and cost was a concern, I'd add up the costs both ways. Maybe you could borrow a 100% argon tank from a friend and just pay for the gas used instead of buying a tank. If costs were the same, I'd sure go with stainless myself, even with mild steel headers. Keep in mind shipping costs for the Jet Hot coating of all that tubing. I'm not sure why headers would drive the rest of the material selection. Remember the headers will stay hotter and are less likely to rust out than tailpipes.

55 Rescue Dog
12-15-2017, 10:16 AM
The headers, and the pipes ahead of the mufflers burn off moisture very quick, but the mufflers, and tailpipes don't, which is where it's a better idea to use stainless. I would think about keeping it simple and mig weld the front pipes, and either temporary mig tack weld the rear stainless pipes, or weld them up complete with steel wire. I'm sure they would last for many years.

Rick_L
12-15-2017, 06:09 PM
I did a little reading on mig welding stainless steel. Seems "tri-mix" gases of varying percentages are the most often recommended. The third gas is oxygen. The majority is argon, with more argon than the usual 75% for steel (often 85-90%). Didn't see any recommendations for 100% argon.

Bottom line, it kind of sounds like you'd have to pioneer it for your own application as to which gas to use. And that would run some $ for a small job. I'm confident you could use 308 or 309 wire, and whatever gas you had on hand to tack the exhaust system.

Bitchin57, were those welds black after doing some wire brushing?

The above is just based on a google search, all my stainless welding experience is with tig and 100% argon. You use 100% argon to tig weld carbon steel too. And I will say this, my limited experience with tig welding stainless is that I've had great results and it welds really nice. For me, easier than carbon steel if you're welding on 16 gauge.

56Mark
12-15-2017, 08:03 PM
I have a very few times welded small parts that were 316 SST to carbon steel with regular steel MIG wire and the 75/25 mix gas. I can't tell it welds much different and after grinding and polishing a little it is hard to tell which is which. The last thing I welded like this was 1/4" SST tubing that I put all thread in the ends which makes great little linkage rods. I still have the original gas pedal linkage in my 56 and needed a rod from the linkage to the carb with a small dogleg offset in it. 3 years ago,I made that rod out of SST tubing and steel all-thread and the weld still has not rusted significantly. I know an exhaust pipe will be hotter and more exposed to moisture but I bet it will last many years no matter how you weld it. If I had a lot of money in exhaust parts and building a nice car I would probably have it TIG'd with stainless.

chevynut
12-16-2017, 07:20 AM
Stainless steel also has a lot lower thermal conductivity than mild steel, so it takes a lot less current to weld it. You get a lot of penetration and a small HAZ with it as a result. I welded my 16 gauge (.065") exhaust with 30 amps and mild steel would take more like 60 amps. It's easy to over-heat it and the welds end up looking oxidized. IMO TIG is the only way to go with stainless if you want show-quality welds. But I think you could tack it with mild steel too.

These are some welds from my exhaust system:

8084

8085

8086