I have a 360 magnum in my '67 dart, did the SL6 swap using Schumacher conversion motor mounts (73-76 style spool type K frame), so urethane not rubber. I'm using TTi shorty headers and 2.5" dual exhaust with H-pipe. The TTi setup has rubber-lined hangers for the tail pipes and rubber-strapped hangers at the axle (using longer seat belt bolts), but from there forward it goes to the header without any other hangers. The down pipe bolts to the header with a 3-bolt flange, and there are muffler clamps at the end of the down pipes, one on the H-pipe connection, and at the front and back of each muffler.
The exhaust system seems stiff to me as installed, even with the rubber in the hangers at the axle and the tail end. I suppose with the urethane bushings in the motor mounts, I shouldn't get too much flex/stress on the exhaust system, but still I perceive a vibration at highway speeds, and I believe it stems from the rigidity of the exhaust. That is, I'm getting some resonance in the pipes and since the exhaust is stiff, I'm feeling it. Otherwise the car is really smooth, I'm sure the driveline is true/straight, the driveshaft is balanced, my driveline angles are good (working angle at both U joints is 1.4 degrees). I assume the H-pipe is adding to the rigidity of the system, since it ties what would otherwise be two independent pipe systems together.
So, assuming I'm correct, and it is a resonance vibration I'm feeling via the exhaust being too stiff, I have some questions:
1. Has anyone else seen this with the same TTi or similar H-pipe or X-pipe dual exhaust?
2. Has anyone noticed less vibration with separate dual pipes versus H- or X-pipe duals?
3. My intuition tells me that introducing flex joints (like in the pic) in the system would alleviate vibration if indeed that is the issue, agree? What about removing the H- connection and making it separate independent exhaust runs, or, replacing the rigid H-pipe connection with a flex joint?
4. Has anyone responding "yes" to bullet 1., tried flex joints and if so, what was the placement(s) and what were the results?
Seems like flex joints are used mostly on transversely mounted engines, but I really don't know if that's true. I have heard of people rigidly mounting their dual exhaust (to get it more tightly situated to the underside of the car) and using flex joints at the end of the down pipes to remove what would otherwise be enormous vibration/stress that would occur with a rigidly mounted exhaust. Seems like that would wear out those flex joints pretty quickly.
I'm interested to hear what people have experienced and their thoughts on this subject. The vibration I'm feeling isn't bad, I'm not sure I can describe how subtle it is, barely noticeable. But I'm particularly sensitive to it, I've had dual exhaust cars with zero vibration, but never had an H- or X-pipe system before. Hmm, how do I describe this...I guess anyone who's been around cars for decades knows the difference when there is absolutely no vibration and a perceptible vibration, albeit nothing bad or destructive, just noticeable. Maybe that helps, maybe not.
Brian
The exhaust system seems stiff to me as installed, even with the rubber in the hangers at the axle and the tail end. I suppose with the urethane bushings in the motor mounts, I shouldn't get too much flex/stress on the exhaust system, but still I perceive a vibration at highway speeds, and I believe it stems from the rigidity of the exhaust. That is, I'm getting some resonance in the pipes and since the exhaust is stiff, I'm feeling it. Otherwise the car is really smooth, I'm sure the driveline is true/straight, the driveshaft is balanced, my driveline angles are good (working angle at both U joints is 1.4 degrees). I assume the H-pipe is adding to the rigidity of the system, since it ties what would otherwise be two independent pipe systems together.
So, assuming I'm correct, and it is a resonance vibration I'm feeling via the exhaust being too stiff, I have some questions:
1. Has anyone else seen this with the same TTi or similar H-pipe or X-pipe dual exhaust?
2. Has anyone noticed less vibration with separate dual pipes versus H- or X-pipe duals?
3. My intuition tells me that introducing flex joints (like in the pic) in the system would alleviate vibration if indeed that is the issue, agree? What about removing the H- connection and making it separate independent exhaust runs, or, replacing the rigid H-pipe connection with a flex joint?
4. Has anyone responding "yes" to bullet 1., tried flex joints and if so, what was the placement(s) and what were the results?
Seems like flex joints are used mostly on transversely mounted engines, but I really don't know if that's true. I have heard of people rigidly mounting their dual exhaust (to get it more tightly situated to the underside of the car) and using flex joints at the end of the down pipes to remove what would otherwise be enormous vibration/stress that would occur with a rigidly mounted exhaust. Seems like that would wear out those flex joints pretty quickly.
I'm interested to hear what people have experienced and their thoughts on this subject. The vibration I'm feeling isn't bad, I'm not sure I can describe how subtle it is, barely noticeable. But I'm particularly sensitive to it, I've had dual exhaust cars with zero vibration, but never had an H- or X-pipe system before. Hmm, how do I describe this...I guess anyone who's been around cars for decades knows the difference when there is absolutely no vibration and a perceptible vibration, albeit nothing bad or destructive, just noticeable. Maybe that helps, maybe not.
Brian
