Should sound good the way you're doing it, and not too loud unless you got your foot in it. 307's aren't renown for hp.
We used to braze together 2 Hawaiin Punch cans with a straight piece of pipe up the middle for our stock cars. Absolutely no sound deading qualities to it, but got past tech inspection. Bob
Buy a pair of 18-24" glass packs, show the mufflers you made to your shop teacher get a grade and go on with life.
I really don't think anyone is going to be able to answer this - You are making your own "Homemade Mufflers" with no sound absorption material, so there is no way anyone can speculate on the sound. I can't imagine it will be much quieter than if you just ran straight pipes. .......
Actually probably louder than a straight pipe, like a burned out glass pack. Nothing in the world sounds better than an unmuffled low compression engine.
You should avoid greasy shavings as I am sure that you are aware. If you don't everyone will call your car the little stinker. The steel wool should last quite a while, depending on what your chips are made from probably as long as your chips. 18-24" is a good starting place for length.
Find a shop that has been running some stainless parts and ask for their shavings. The outer shell will probably go away before the packing.
Your ram horn exhaust manifolds are probably the smallest diameter of the ram horn family. but 18 inch to 24 inch on the muffler would be my guess with louvers punched to catch the exhaust on the way out. As others said a packing material that will stand up to the temps installed between the outside pipe and the inside pipe. I am using about 24 inch glass packs on my car with ram horns, but the exhaust goes all the way out back. It has a nice rumble to it, but I can still talk to someone in the car at speed. Good luck with your project.
If you are asking about my car it's a 400 small block truck engine stock. Maybe 200 to 220 horse power, and 2 1/4 exhaust all the way out. I like the drill and pry idea the best, and a filler plug installed in the inner pipe with a smaller diameter holes drilled around center or a larger one in the center of it. This would create a baffle affect and should reduce your noise. You wil need the other holes drilled the way your pic shows it. More plugs less noise. lake style baffles are built the same way except they use about three of the baffle plugs with no pipes or mufflers.
In your picture they are referring to a freeze style plug inserted in the center of the inner pipe that forces the exhaust out of the drilled holes of the inner pipe to the outer pipe area, then your filler material if used, plus the sealed end of the outer pipe baffles and forces the exhaust back into the inner chamber and out to the back of the vehicle quieting the noise. This is the plug I am referring to, but what I am saying is drill some small holes in it so you dont get too much back pressure and this should also achieve a little hot rod rumble to your set up. More of these plugs the quieter the car, but in you application more might be too much.
I think 24 inch if built this way should be fine, any more would be over kill. I'd like to here it after it's done.
I would use one spacer and it probably doesn't need to be 1/4 inch thick, but it wouldn't hurt, if you do use more than one I would space them out about 2 inches apart. and the holes should be 3/8th no smaller and numerous amounts of them. My glass pack are open all the way through and the muffle comes from the louvers bent inward in the inner pipe and how they grab the exhaust and force it to the outer pipe and then back in. Same principle design except you are gonna use a plug to force the issue and shoot for a quiet exhaust with less pipe. Should work. Again good luck
How are you going to keep the "shavings" from blowing thru the 2" inner core? Instead of using a inner core have you thought about chambering the inside w/baffle plates or some angle pieces to split air flow. Lets face it you are not really concerned with flow since you have a low HP 307. This might even provide you some needed back pressure for added torque.
If you can't get enough stainless shavings from work, you can use stainless pot scrubbers for a filler also. I made some simple perforated inserts to slip inside some lakes headers and they were a lot quieter with the filler (fibreglass in this case) than without. How about making the rear of the mufflers removable rather then welding them on? Then you can try them out empty and then experiment with different fillers until you are happy with the sound. Here is what I mean in a picture. Slip the back section (blue) inside the front section (black) and secure with a couple of screws through the flange.
The tighter you pack them the less it is going to muffle, just pur it full and put the end on. A steel pack is not louder than a glass pack it just sounds different. the reason they started using glass strands was because the steel packing would rust away and the glass would not rust away.
You want little stickin' up thingies in your eshaust flow for best results. Kind of like a louver on a hood wiith the stickin up parts facing the inlet. I am not going to use terminology that makes any sense to someone who understands sound deadening but the little raised parts need to scoop the exhaust into the packing. That's not how it really works but you understand right?
This is an original Smithy's muffler demo cutaway, showing what used to give them the sound they were famous for. Notice the chambers, that are on both ends, adding some resonance. Today's reproductions only have the outside appearance and chambers in common with the originals. Today they have a much smaller diameter louvered inner tube with dense glassfiber packing, giving a very different sound to the originals.
Inner tube and donuts are one piece that slides, creating the two empty chambers at the ends. If you do this, make a sound clip. We haven't heard the original Smithy's sound for a long time. If I had a machine shop, I would have people send me their new repros and modify them custom to length with the original type of construction. My main issue with the new ones is the small constricted 1-3/8" inner tube with hole louvers. The original 2" inner tube and slotted louvers should have a much deeper throatier sound, without the choking narrow restriction. To get closer to that, I had Porter make me a custom 14" pair with his larger 2" inner springs and 4" outer casing. Best muffler sound I had so far, but I am still curious how chambers on both ends would sound, like the Smithy's have. Btw: I make custom guitars and tube amps, so forgive my obsession with sound generation...
I made a set of baffles for my 23 with Limefire headers similar to what you described earlier. I used a couple pieces of exhaust tubing that I drilled a bunch of holes in then I used a punch to pry the holes into scoops. It really did drop the sound down to a fairly acceptable level. We have also been experimenting with stainless steel scrubby pads that I bought at the local restaurant supply house. They are only about 70 cents each, but the problem is they end up shredding and blowing out the holes in the header. Still some work to do on that idea. Don
I have seen stainless or carbon-steel matts available from motorcycle muffler supplies, which work better than scrubbing pads. That's what the steelpack muffler makers use for car mufflers. Sound chambers on the ends will give a louder more resonant sound. That's part of what made the Smithy's sound popular and they described it also in old advertizing. There was at least one other muffler maker doing the same. Maybe Hollywood or Walker mufflers ? I think they advertized it as 'motorboat' sound in their ads. Porter's don't resonate like that, but have a unique rippled-roaring sound from the inner springs. They sound very smooth and mellow at low to moderate rpm, but get more nasty at higher rpm and open throttle. Perfect for my coupe.
As the exhaust flows thru your baffle/louver core and the sound is absorbed by the "shaving", the "shavings" will be moving around from exhaust flow and engine vibration. Think of rocks in a open coke can(or beverage of choice), if you shake the can the rocks will come out. So what keeps the "shavings" from eventually working their way thru the baffle/louver core and into the direct flow of exhaust. You will be better off with steel wool or fiberglass mat. 2nd suggestion-no inner core at all. Just use a couple baffles with holes(think of a washer with extra holes) and then just add some angle air flow dividers to split the exhaust flow. This style muffler will give it a deep tin can sound, but expect some cruising drone.
I used the packing material made for repacking motorcycle mufflers on my other car. just like a baffle system on a round de rounder car. sound good, yet doesn't cause too much back pressure.
Interesting post. It is fun to make your own stuff. Good for you. Just my opinion, but as mentioned earlier about the Rams Horns, if they are indeed the smaller ones, I would find a pair of larger ones for better flow. I am using 2 1/2" Corvette Rams Horns on my 283, which is bored .60 over, cam and other upgrades and running 2 1/2" exhaust all the way to a pair of Smithy's mufflers with the flanges opened up at each end.....Can't swear that they make a whole lot of difference performance wise, but I like them, as well as the cool factor that we all want, even if we don't admit it. (I know they are there, so like it) Good luck on your project. I sounds like a lot of fun... Cheers..... On EDIT: My Smithy's are the correct old style, that I bought from a fellow that had them new in the boxes from many years ago. Using the 2 1/2" pipe all the way, and exiting just in front of the rear wheel gives me a very low growley mellow sound. Not the crackling of the old glass packs.....I really like it.
Honestly this is a lot of wasted time and effort. Just buy a pair of Porters and install them then move on. Besides, you really seem not to understand the concept. Especially when you talk steel shavings. They do not use steel shavings, the type you would get off a lathe or a milling machine, they use steel or stainless wool which is vastly different. And in the operation of a muffler the gasses do not need to flow through the packing to give a muffling effect, the size and length of the body along with whatever packing is there give the muffling effect by absorbing some of the sound of the combustion explosions as the gasses pass through. As in Porters design of a tightly wound spring with steel wool packing around it. Like I said, buy a pair of mufflers and keep it simple.
Im all for building your own stuff, but companies put a lot of time and $ into R&D. Im gonna let them do the work and Ill just buy some. But it sounds like a good project and youll learn something.
If you ever get around recording the sound of them, please post it. I have used my digi-cam in 'movie' mode before, laying it on the ground behind the truck a few feet away and its works well for sound recording. I personally would not use any restriction plate or too narrow inner tubes in the straight-through muffler style, especially with larger engine displacement. I know there are baffling inserts for straight pipes, but I personally don't like the idea of exhaust restriction to reduce noise. There are mufflers with chambers and internal baffles oriented in all sorts of ways to create signature sounds for various brands, but they all use a large chamber and inputs and outputs not directly in line. They all cancel certain frequencies and allow others to pass through along with the gases. As another post describes, the straight through type is not supposed to restrict the flow, but uses an absorption material wrapped around an inner tube with openings so the sound waves are absorbed, but the gasses can pass. The longer they are the better they do this and will be quieter. Cherry bombs use a perforated inner tube which gives even less restriction than louvers, so they flow better and are also louder at the same length. Also, if your engine runs a little rich and produces more carbon in the exhaust, it will over time clog whatever absorption material by the openings and the sound will keep getting louder.
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