zgeezer Posted January 3, 2007 Share Posted January 3, 2007 I've read the previous posts on exhaust pipe resonance and "drone". I'm designing my exhause system and would like some input. The vehicle is a '70 240z, which is now a stripped bare shell. Sound attenuation will be added to the shell, but for now I wish input into the exhaust system only. I think this will produce a quiet exhaust, but I really want some comments. Engine: 2004 LM7 Chevrolet 324 ci or so. Stock. Sitting around since 2004 waiting for installation. Parameters: Absolutely NO drone between 1800-2550 rpm, which is where I expect to cruise on the highway. Quiet outside: I don't want to advertise as a v8 swap. Visually, must look old school. Headers: Short block huggers by Sanderson for the JCI LS1 swap, which are on my garage wall or stock cast iron truck manifolds. It appears the stock manifolds will fit. I've been told that block huggers add very little hp over ls1 factory manifolds and are "noisy". I like their looks, but I could go with the stock cast iron. The current design would run duals with a 3' down pipe for a collector of about 10 inches. A flanged car chemistry 3 disk insert in each collector. The 3 inch pipe reduced to 2.25" on both sides into an "X" or, "H" pipe depending upon clearance [perhaps a flanged "H" pipe just after the reduction from 3.0 to 2.25. I think the "X" will fit just after the AT pan. Each 2.25 inch exhaust pipe into a dynomax reversible SS muffler with two 2.25 inlets and one 3.00 inch outlet. For those of you running a Chevy Gen III engine, did you use either an "H" or "X" pipe and where did you run it. This engine is stock and, which the exception of a twin screw supercharger, [Whipple design] will remain stock. There are several Eaton or Whipple based superchargers available for the Chevrolet trucks. I'll be using one of these at about 8-9# of boost and no intercooling and it is a consideration for the design of the exhaust system. My partner doesn't fuss about the $ or the project car AS LONG AS she can parallel park it; listen to her music, carry on a conversation, and have good heat and a/c. I understand that exhaust pipes/mufflers will set up sympathetic resonance in the car body, but I'll handle that once I have a design for the least amount of resonance from the pipes. Sorry for the long post. g Quote Link to comment Share on other sites More sharing options...
Bartman Posted January 3, 2007 Share Posted January 3, 2007 Here's how my 'x' pipe is installed on my LT1 exhaust. I'm running dual 2.5" exhaust exiting on either side of an F-body LS1 gas tank. There are more pictures at my web site: http://mysite.verizon.net/bzandbergen/Exhaust.htm Quote Link to comment Share on other sites More sharing options...
zgeezer Posted January 3, 2007 Author Share Posted January 3, 2007 Bartman, Thanks for the photos. I see that your differential cross member has been modified, allowing you to mount the "X" pipe high into the tunnel. I might be able to do something similar with my long nose R200 if I use a "Tyler" mount. Two questions: With this system, do you have a resonance/drone in the cabin? If so, at what rpm range? g Quote Link to comment Share on other sites More sharing options...
Bartman Posted January 3, 2007 Share Posted January 3, 2007 ...Two questions: With this system, do you have a resonance/drone in the cabin? If so, at what rpm range? g I haven't noticed any resonance/drone in the cabin...but my exhaust tone is nowhere near stealth. Quote Link to comment Share on other sites More sharing options...
datsunlover Posted January 4, 2007 Share Posted January 4, 2007 I would say go with the stock manifolds.. Headers look cool, but make noise and heat. (no mater what they are in) As for muflers, I was impresed with the flomaster 50s my buddy put on his 04 Ram. I've found pickups w/custom or aftermarket exhast to be pretty bad for 'drone' on the highway, with lots of resonation... but unless he was standing on it, you'd never know it was a Hemi! Very quiet around town, and you couldn't hear a diffrence at cruising speeds from the factory system. Now, after about 2500 it would ROAR like an angry bear, but hey.. thats ok by me! I don't know how you're going to 'mask' the sound of the S/C though.. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted January 5, 2007 Share Posted January 5, 2007 ...or stock cast iron truck manifolds. It appears the stock manifolds will fit... g Is anyone running stock truck manifolds? Anyone know if they fit for sure? Just curious if you have tried them on an LS motor sitting in the engine bay. I know on my L6 it was the headers that made the nice glub glub idle sound and droned at cruise speed. So it would make sense that stock type manifolds would be the first step to avoiding the droning sound. Quote Link to comment Share on other sites More sharing options...
getZ Posted January 17, 2007 Share Posted January 17, 2007 I run dual 2 1/2's up until the muffler where it is dual 2 1/2 in, single 3 1/2 out. Up front I have a pair of dynatech cats to an H - pipe (I couldn't get an x pipe two fit with two moroso spiral flows). So it goes header to cat to spiral flows to spin tech muffler. This car is still not quiet enough to hear the radio well without cranking it up quite a bit, even with sound matting added to the floor boards. I will probably land up redoing the exhaust and go with packed mufflers instead of resonant chambered mufflers. The problem is getting them to fit underneath inside the transmission tunnel. I may even opt to modify the floor underneath the seat going back to gain more exhaust room. Quote Link to comment Share on other sites More sharing options...
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