Let's talk custom exhaust!

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Standing on the corner
Aug 21, 2011
Dittmer, Mo.
I've got to get an exhaust made up and going with stainless steel. any opinions on grade of stainless, 304 or just 409? Any opinions on a muffler. I got a guy, who uses Magnaflow mufflers, but says they're on the loud side. I don't want loud.

How about diameter, 2 1/2" or 3". Remember I have the Chevy LS motor.

Any other things I should know.

Thanks for any input.
Also, sure you've done your own research. 304 is a more superior stainless but typically pricier. I've only ran 409 as finding all the components to match 304 is more difficult.
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Ron, I did a 2-1/2 inch system on my 80 series with Borla muffler. Bought as a hot rod kit with all you need for custom, only thing else was flanges from Pypes real heavy duty. All 304 series stainless.

Thanks Bob.

Like the others I prefer 2.25” - 2.5” for petrol engine exhaust, I’ve used the 50 series Flowmaster in the past and like the way it was reasonably quiet until you stomped the gas then it had a good sound.

A few things I thought about when doing the exhaust on my pig, I used 304 SS but I would have used 409 as long as it was 16 gauge I don’t think it’s going to make a big difference for what we do (FYI, I had a difficult time finding 304 16 gauge mandrel bends), I used 4 sets of V-bands to separate my exhaust pipe into four separate components so maintaining or repairing major components like the transmission is possible without busting out the sawsall ( I prefer the PPE V-bands with the inner mating ring but any will do), strong mounts that are easily replaceable and flexible enough to not stress the pipe is something most shops overlook when they weld straps with grommets to a 4 wheel drive vehicle exhaust systems, I made my mounts from ½” 304 round stock and formed a U shaped strap the straddle the pipe then used Walker 35229 exhaust insulators (basically I mirrored the modern factory exhaust system with aftermarket components), I also added a wideband O2 bung so I could use an “Innovate 3844 MTX-L Digital Wideband Air Fuel Ratio Gauge” for tuning my engine, this is a handy inexpensive way to get the most from your engine and you have the option to permanently mount the gauge or just plug it in while tuning and plug the bung when you're done.

Looks like you are already looking at a flexible bellow joint so I have nothing to add to that.
All good information Guys! I've talked to different shops, with different quality and ranges from $2500 to $800. I really like the idea of picking my own parts and having somebody put it together. The one shop buys the mandrel bent tubes and tig welds it, more for custom hotrods. I'd like to try it myself, with the mig, but worried about leaks and wasting a lot of money, then having someone do it. The cheaper shop bends their own and uses 409 stainless, I need to talk with them again about upgrades.

Thanks for the good guidance!
Ron, mine was under a Grand including the Hotrod kit (enough for 2 trucks but you have V-8) Borla muffler, Magnaflo cats x2. And I mig welded it in driveway.

Thanks Bob.
I built my own for two reasons, first was the satisfaction of building something good or bad I can say I did it. The reason I start this project to get me out of the office and into the shop so I’m doing as much of the work as I can, not so much to save money but to give me something to do. Second there is not a shop on this planet that would have dealt with all my anal-retentive quirks on how I wanted it done.

I TIG welded mine but MIG would have worked just as well, if you purge the pipe while you weld it will help keep the dingle berries to a minimum.
Did you guys butt weld or over lap the pipe joints? I'm guessing butt welds. I've got to go under the oilpan and connect with the other side, so would need a lot of different angle bends. 16 ga. wouldn't be hard to weld and I do like to make stuff myself. I tend not to get TOO mad at myself.

Did you tack weld the pieces in place and then weld up on the bench or driveway?
Butt welds, I tacked all the parts together then pulled out and welded on the bench. FYI adding the V-bands made this much easier.

Single exhaust. I'll have to cross over under the oilpan. No cats, but will need O2 sensors.
I'll cross over to the driver's side and run down. All my fuel, brake, air lines are down the pass. side. The only good place to cross is under the oil pan. It's been done a million times, just not by me.

Always wanted to do this, just didn't want to take the time. Guess I'll jump in and see what happens.
Will it still have the classic American V8 burble with a single pipe?
Well, I've got all the lines run down the pass. side and really don't want the heat by them, not to mention the front driveshaft is in the way.

David, my old 40 with a 327 sure had it. This time around, I'd like it to be a less noisy. I don't know why, since I'm half deaf anyway.
If your going to go single exhaust I would go 2 1/2 to your y pipe. Then 3 inch back from there. Otherwise it's going to have quite a bit of back pressure.

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