Had this idea rolling around in my head for years, saw a few similar posts on making baffles for pipes here on The HAMB, & finally figured I'd try out my idea. I started with a few extra feet of 4" exhaust pipe & 2-1/4" exhaust pipe & some flat pieces for the ends actually made from s****s of 4" pipe. (first two pics) I laid out some marks on a roughly 2" distance and sliced 'em up with a cutoff wheel. I then used a cold chisel to dent them into the exhaust path and scoop the exhaust from inside the 2-1/4" pipe to outside. There's a couple of pics of what I did. Nothing scientific, just basic & crude. I only did this on two opposite sides. On the 90* off sides, I used a sharp punch to just deeply dimple the tubing - don't ask why, I just did it. It seemed like the right thing to do at the time! (next four pics) Standby for segment #2!
Next, I cut out the end plates to slip over the 2-1/4" tubes and welded them inside the 4" pipes. (First three pics) After finish welding them, I trimmed the end plates & ground down the welds. (last pic) I put them on my flatty & they sound really good! I was going to put some steel shavings in them, but figured I'd blow them out or it'd be too quiet. I just wanted something to knock the edge off open pipes & these sound good! Not super original, but not bad for an afternoon's work... Enjoy!
Great tech stuff! Have you ever done any experimenting with different patterns for the "scoops"? I'm wondering if having the scoops staggered might help scavenge more of the exhaust pulses since the scoops would be spread across more of the width of the exhaust flow. Anybody done something similar?
The car is running like **** right now, but I'll see what I can do - very busy at work, so little time for car stuff....I'll see about getting a vid/audio file up.
pretty cool job and even cooler post but with the steel prices in switzerland its cheaper to get a set of smitheys :-(
Naw - first time I've even tried it, but it would make more sense to stagger them - every row 90* off from the previous row... Maybe tomorrow I can get a sound byte up on the web somewhere...
One thing to keep in mind... the exhaust flow and the sound pulses are two different things. A muffler will quiet things down even without flow. In fact they are often tested on benches that provide sound but no flow. Since sound is pressure, simply having openings in the smaller tube is pretty effective. The sound/pressure will find them whether they are in line with the flow or not. You don't really need to "scoop" anything up, and scoops can add flow noise at higher rpm. Not that it matters usually, but they also add restriction. Spreading them out around the tube will effectively make the tube smaller from a flow standpoint. Perforated tubing wrapped in fibergl*** is very effective at higher frequencies and the 'gl*** doesn't change the low frequency response much from an empty chamber. Rock wool (basalt) is even better. Steel wool also works but isn't nearly as effective. The problem with perfs is... if you don't wrap them, they can whistle under some conditions. Some exhaust companies have used slots rather than round holes. Some put dimples in the tube to trip the flow and prevent whistles. This isn't to say scoops are "wrong". If they sound good to you, great! Mission accomplished! I'm just saying... you don't HAVE to shape scoops into the tube. The sound doesn't really care much. And the scoops could just as well go OUT from the tube - OEMs do this with louver tubes. When it comes right down to it... you don't always even need the smaller tube. An abrupt change in area will quiet things down. Just the opening at the end of the tailpipe does a lot to quiet the exhaust down. All of the things mentioned will have an effect on sound, so I'm not saying they'll all sound the same... but it's more a case of different strokes for different folks than one way being universally "better" than another. They all have pros and cons...
I didn't take pics of them, but I did dimple them 90* to the scoops - don't ask why, just seemed like the thing to do at the time. Hell, I was making it up as I went...
Running a bit rich & the carbs aren't dialed in yet...yada, yada, yada OK - hopefully, this youtube link will work! OK - there's supposed to be an embedded player there - got the 'yt' tags & the embedded details from the youtube page, but it's not showing up...here's a regular link: http://www.youtube.com/watch?v=7vlNyIS8jDE
Thanks for sharing and the effort you put in. Thought the video of your car with the mufflers was great. Nothing to do with the muffler tech but the video also on the site with the coupe goin down the road was fantastic. Great stuff.
cool! yer gonna put smithy outta business with that stuff. bet that's how it all started. imagine if nowbody ever invented the muffler. what? what?..
im doing this. has anyone tried stuffing some fibergl*** shreds in there, like homemade gl***packs? er sort of.
Nothing in life is new, I have been building mufflers the same way for 30 years. I started doing it because I did not have a lot of money when I was young. You are right, for some reason it works perfect on flatheads. I once built them into a set of headers on a street rod. Looked sharp and sounded nice and got rid of all the **** hanging under. Keep up the good work
You need to find some fibregl*** cloth or matt - shreds will just blow out. Have also heard of folks using those stainless kitchen pot scrubbers too. I thought about it & figured if it was too loud (which it's not), I could open 'em back up & add whatever I wanted in there...
FlatErnie, that is awesome. I have been building very special mufflers for a few years now too. They were used originally on 70 GTO's. They are dual mode, loud and quiet, and vacuum actuated. They are fun to do but very expensive (st. st.) and even more time consuming as you likely found with yours. I have plenty of spare things that might help you tone yours down or change the overall sound if you are interested. Tom
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