LSA or Duration to fine tune glasspacks??

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I have glasspacks on my 340 valiant and it sounds nothing like the Hondu or ru.
 
Come on guys. You know better than this.

If you age going to go full baller/tuner and use glass packs, you ought to be using the 1970 LT1 cam with the 116 LSA.

You guys should be in the right era on this stuff.


And to whoever posted the puke face...that **** is just nasty. Looks like he was drunk with the flu
 
just say no to glass packs,..wanta bring back turbo muffles id under stand but glass packs i dont get might as well run straight pipes...
 
These are cheap thrush glasspacks on my cammed 5.3 '89 Formula. Terrible muffler, but the previous owner put them on to get by. I have LTs and a SLP Loudmouth going on it. If you are determined to go with a "glasspack" go with a Borla XR1, Dynomax bullet, Magnaflow, SLP, etc. All they are is a fiberglass stuffed straight through muffler, also the longer the muffler is, the worse they sound IMO.

Building a motor around exhaust sound is definitely the wrong way to go about it. Build a good motor, and it will sound good every time.

 
yellow rose said:
Come on guys. You know better than this.

If you age going to go full baller/tuner and use glass packs, you ought to be using the 1970 LT1 cam with the 116 LSA.

You guys should be in the right era on this stuff.


And to whoever posted the puke face...that **** is just nasty. Looks like he was drunk with the flu
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NO! NO ! NO! DUNTOV 30-30 Get it right man! :D
 
put some Thrush mufflers on it ans some highjacker air shocks and some slot mag wheels hanging outta wheel well 4 inches,..dang im starting to miss the 70s,..put some pink angle hair on the dash mannn,...where my bell bottums at??
 
318willrun said:
when it goes "thip thip thip thip thip", it sounds like a burnt valve 273 2bbl.
when it goes "thap thap thap thap" , it sounds like a 10.1 340 up to snuff.
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I have a sound clip of my 360 that may be aligned with the thap thap thap... Will upload it when I get home (I too want know if it sounds right)
 
elementaltoad said:
...Building a motor around exhaust sound is definitely the wrong way to go about it. Build a good motor, and it will sound good every time.
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First, no one here (I tend to think) would argue that...

But, if ya hadn't noticed, this thread is purely tongue in cheek ;)
 
elementaltoad said:
These are cheap thrush glasspacks on my cammed 5.3 '89 Formula. Terrible muffler, but the previous owner put them on to get by. I have LTs and a SLP Loudmouth going on it. If you are determined to go with a "glasspack" go with a Borla XR1, Dynomax bullet, Magnaflow, SLP, etc. All they are is a fiberglass stuffed straight through muffler, also the longer the muffler is, the worse they sound IMO.

Building a motor around exhaust sound is definitely the wrong way to go about it. Build a good motor, and it will sound good every time.

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I said "thip thip thip" with your car, and then I tried the "thap thap thap thap". Sorry, but the "thip" fit it. Listen to your video and try saying each one. You'll find you are a thip. I don't want the thip, I want the thap. Now to change that, do you need more LSA and less duration??
 
318willrun said:
I said "thip thip thip" with your car, and then I tried the "thap thap thap thap". Sorry, but the "thip" fit it. Listen to your video and try saying each one. You'll find you are a thip. I don't want the thip, I want the thap. Now to change that, do you need more LSA and less duration??
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I rewatched the video and I definitely get the thip vs the thap - milled heads as much as possible, stuff in a big cam, you'll get tons of thap! I think you are going to want to mill the heads so you can bump the compression to something closer to 14:1 and run as much duration as you can. My friend's neighbor did it and ran 8s in the quarter, stock longblock, in a full weigh car.
 
What you need is an early opening exhaust valve and a bunch of overlap to mess it all up. How the engine responds to that don't much matter, cuz performance is all about the idle.
But I must say big pipes seem to mellow out the sound of a big cam. I think all that exhaust energy still left by the early opening exhaust tends to arrive at the back bumper with a whole buncha lost energy. And I think those big pipes convert more of that energy to heat. So now you can play with tip shapes to change the sound into something you like.
If you noticed that 4banger example, the tip was rolled over into itself and this makes the worst kindof racket. And the smaller the pipe the worster it is.
But the original 340 type rectangular tips make an interesting burble, even with the stock 268/276/114 cam.I don't personally like it, but many do.
Shot gun tips or boom-tubes, well they are just flat-out nasty megaphones. If they are long enough,straight enough, and just the right diameter,and the engine is making plenty of exhaust energy, they can do tricks. They can make a nice thoop-thoop at idle, that turns into a fairly pleasant sound when cruising, and a raucous roar at WOT.
But my favorite is a 3inch,turn down pipe. This will make a mellow sounding 360, with just barely hinting at the cam. Again, the cruise will be pleasant to all those driving around you, with many people driving in just the right position next to you to enjoy the musical tone coming out of there. But when you stand on it, it will strike pure terror into the heart of your hapless victims. And somewhere between 6000 and 7000 it will shriek like a banshee, and even satan himself will cover his ears and plead for mercy.
Ok so I have run three different cams with three different Dcrs, and all the various differing valve events,thru this same full-length dual 3 inch system with turn-downs. No glasspacs cuz, well, let's not say. But the Dynomaxers on there sounded pretty much the same with all three. I sorta remember the 292/292/108 cam having a bit more rumpidy-rump to it, but honestly, I wasn't paying much attention to the sound back there. Besides idle rpm plays a really big deal on the idle sound.
When I crank back the timing from the drivers seat, so that the rpm gets down to 650 or so then my current 230/237/110 cam starts to reveal itself. Then letting out the clutch, and letting it pull the car outta the parking lot at 550 or so, well then I guess I can hear the thap-thap; but mostly, I'm not paying attention. My mind is already planning my next maximum-impact exit. Just kidding.

So my take on this is; in a streeter with a real street cam,you are gonna have to try waaay too hard to make that thap-thap lol sound. And neither LSA nor duration will play any significant part in the equation.I'm talking street type cams of less than 240* duration. I think the sound is more related to how much exhaust energy reaches the back-bumper,how separated the pulses are,and the idle-speed itself. Of course you have to have headers, to separate the pulses into nice little slugs of energy. And if you pile them all up in a 3-pass muffler and jam them into a 1.875" pipe; well then by the time they get to the back, then it's like a crowd of people trying to exit the stadium through 2 gates; a lot of pushing and shoving, with not much action.And the crowd gets all backed up to homeplate.
 
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AJ/FormS said:
What you need is a late closing intake valve and a bunch of overlap to mess it all up. How the engine responds to that don't much matter, cuz performance is all about the idle.
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it's all about maximizing the sound of the glass pack. Nobody scared of the thip, but the thap will help avoid eye contact.
 
sounding angry at the stop light is definitely worth some street cred.



Even if all you do is putt away.
 
Shouldn't have to sacrifice performance to tune the glass pack sound. I'm thinking a little less Lobe separation and more duration. Fast ramps too, you want the valve slamming shut to get the Thap Thap Thap. At least that's what i'm think'n.....
 
Gotta agree with AJ on the turn downs and if you live in the city theres no feeling in the world that compares to driving down an unlit street with the lights and horns of the car alarms from the parked cars going off as you rumble past . Damn I miss that I'm going to have to put mine back on for a couple of nights.I'll say hi to the neighbours for y'all AJ .
 
@AJBut my favorite is a 3inch,turn down pipe. This will make a mellow sounding 360, with just barely hinting at the cam. Again, the cruise will be pleasant to all those driving around you, with many people driving in just the right position next to you to enjoy the musical tone coming out of there. But when you stand on it, it will strike pure terror into the heart of your hapless victims. And somewhere between 6000 and 7000 it will shriek like a banshee, and even satan himself will cover his ears and plead for mercy.

When I crank back the timing from the drivers seat, so that the rpm gets down to 650 or so then my current 230/237/110 cam starts to reveal itself. Then letting out the clutch, and letting it pull the car outta the parking lot at 550 or so, well then I guess I can hear the thap-thap; but mostly, I'm not paying attention. My mind is already planning my next maximum-impact exit

Brilliant!:thumbsup:
 
Alright, here she be at idle and a bit of rev. Sorry for the poor sound quality, it was recorded on an iPhone microphone. This was recorded in early to mid June 2016:

What do you think?
 
Not sure lol it has a lunati vooodoo cam in it. The engine builder recommended staying around a 280 duration. lemme see if i can find the cam specs. Keep in mind this is with hi po manifolds and accurate true duals with two gibson performances mwa mufflers


  • Advertised Duration (Int/Exh): 268/276
  • Duration @ .050 (Int/Exh): 226/234
  • Gross Valve Lift (Int/Exh): .494/.513
  • LSA/ICL: 110/106
  • Valve Lash (Int/Exh): Hyd/Hyd
  • RPM Range: 1800-6200
  • Includes: Cam & Lifters (#71977PR-16)
 
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My first car was a 1967 Belvidere II convertible with a Poly head 318 ( must have sold new in Canada). I found an Iron 4 BBL intake in a junk yard, installed a Thermoquad with an adapter plate and dual exhaust with glass packs. It was the best sounding exhaust I've ever had on a car. I don't know if the Poly head had anything to do with it, but it had a nice purr at idle, never droned, and was not overly obnoxious. It did get loud over 5000 RPM with the TQ low growl and the exhaust rapping away but it never had the nasty glass pack sound
 
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