I have a 70 GS with a 455 and a m-20 trans. 2.5 inch mandrel exhaust with an x-pipe and Stainless flowmasters. I am having an exhaust drone at idle. it is very annoying and I can't seem to get rid of it. I just put the x-pipe on in place of the h-pipe I had previously. The X made a huge difference, it got rid of most of the vibration at cruising speeds, but I still have the drone at idle. I am running a 750 edelbrock performer carb and the timing is at 11 degrees. any ideas?
Take it to a muffler shop, crank it and let it run while on a lift. Then you can feel around with leather gloves and see what makes a difference. The drone is cause by resonance of an audible frequency at that engine RPM. (Humans with good hearing can detect from about 20 to 18K Hz) It may be solved by a change in clamp placement, but it could take say a change in muffler from say a short case to a long case.
Drone on... I thought the dreaded exhaust drone was what made people switch away from the Flowmaster mufflers??
I do not care for Flowmasters myself--a catchy name though. I like Dynomax which is made by Walker. Some tests published by I believe Torque Tec showed they flowed better and were quieter than FM mufflers and all things considered the long case may flow better than the short case mufflers. So I like the 20 inch case Dynomax. I have personally installed a set on a GS and they will fit just fine. I did have to buy a big pipe cutting tool but with the appearance of Harbour Freight we are not talking much money. I did mine on jack stands but a lift would take the sting out of it. No more than muffler shops charge-- I had an x pipe installed for $60-- it is worth it to get lift access. Without getting into the phenomenon of resonance too deeply, it appears on aircraft control surfaces and venetian blinds too and we call it flutter. Also there is a parallel in the design of electrical circuitry where we retain the name resonance. In the electrical world we tune the circuit for resonance by varying the values of components such as an capacitor while in the physical world of say aircraft we may have to add a weight bob to the control surface. Much is trial and error . Likewise in the exhaust system world for sound a component such as pipe length or diameter or muffler lenght or design may have to changed on a trial and error basis. If it is not a clamp or say a leak issue, the easier solution is a muffler change because it is more difficult to change the exhaust lenght or diameter dimensions.
I have T/A Shorties, 2.5" system and an X-pipe, I run long case Magnaflows, zero drone. I'm with Jim on the longer case mufflers, they make a huge difference in sound control and in many cases out flow the SoundMas..I mean Flowmasters:laugh:
Len: I admire their marketing acumen for coming up with the name Flowmasters, but they are more accurately described as "Loudmasters" or in this case perhaps "Dronemasters". Heck, anyone can design a loud muffler. It takes some thinking to design a quieter one that flows.( Gee, I am glad I do not feel strongly about this issue. ) Incidently, even the Dynomax will let everyone know when when you have called for the ponies to all gallop.
x-pipe and vibration I am very interested in what type of vibration you were feeling that was eliminated by the x-pipe. I have ta headers, torque tech 2 1/2 inch exhaust with flowmasters. I have some vibration that I was told by my engine builder is related to the headers and exhaust. Very, very curious as to what was going on with your car prior to the x-pipe. Thanks.
Been there, done that, they droned like a ***** on Mandys GS, you couldn't talk over them. They work good on my truck now, just have extend the tailpipes 8Ft past the passenger compartment. Long case Ultra-Flos work very well and sound nice......
I did have some serious vibration before i put in the x pipe. At 80 or 90, the car was a vibrating mess. I actually had a new driveshaft made thinking that was tyhe problem. the x-pipe cured it. thanks to Jim Burek at PAE for the advice on that one. Its a totally new car with the x, but I still have the drone at idle. Before the x, i had flowmasters american thunder h-pipe setup. that is what was giving me the vibration. Go with the X, you should see a difference. I am going to order a set of dynomax mufflers and see what that does for me. thanks for all the replies, flowmasters are not the way to go i guess!!
I had to go to 3 chamber Flowmasters to quiet mine down. I'm running 3' mandrel bent pipe with an H and the 2 chamber ones were way and I mean way too loud. The 3 chamber setup is quiet out on the road until you hammer it. The headers ping pretty bad at idle but that is the nature of headers. Been thinking of an X pipe for the future. Mike D.p
I would look for pyhsical metal to metal contact causing that idle drone. I have 3" mandrel bent pipes, right now with no crossover and there are several areas where there is very little clearance. Look closely where the tail pipes go over the axle tubes near the upper control arms and also verify that none of your hangers are contacting anything. Good luck!:af:
Dave, I will check all my clearances. JW told me my exhaust runs too close to my high tech, 12 year old, piece of crap air shocks and that I need to lose them ASAP. If I wanted an x pipe, which one works well. I looked on the net a DR. GAS unit. Any thoughts or recommendations. Thanks.
Robert: Just installed a Doc Gas on a 70 convt. NASCAR uses them. Easy fit. I ordered it from Utah and a muffler shop put in on for $60. Make sure they have installed one in the past.
crossover Just last week I was looking for a part for the truck I drive and happened to stop by a heavy duty truck parts house and to my suprise they sell mandrel bent aluminized exhaust parts for big trucks in different degree's of bend like 45. 37. 90 and so on. Smallest they had in stock is 2.5" but my pipes are 3" anyway. For almst dirtcheap someone can purchase the components for a "X" crossover and say them favorite words. I did it myself! I'm going to. A good friend of mine runs a muffler shop and he can cut and weld with the best of'em. Just his crush bender cant make good bends in big pipe. Oh boy I'm gonna have a "X" crossover soon. Yee haw :Brow:
Jim, Appreciate the recommendation, ordered up an X from Dr. Gas. I'll let you know how it works out. If nothing else it looks damned impressive. Thank goodness the wife doesn't know about this website. I do divorce work, but don't need myself as a customer.
Gentlemen: First of all, thank you all for your help. For going on three years now I have been trying to eliminate the vibration in my car. It got so bad, at one point I decided to throw in the towel and sell my car just to avoid the aggravation. Based on the recommendations from the board, and that of Jim Lore, (one hell of a nice guy) I ordered up a Dr. Gas X-pipe, fully expecting that it wouldn't work. Well, imagine my shock when I picked up my car and found out that the vibration that had haunted me for almost three years WAS GONE. DONE. OVER. ENDED. The car idles more smoothly and sounds great. Over the weekend I took the family out in the ragtop and fell in love with it all over again. I literally had more fun in with the Stage One this past weekend than probably the first 15 years I've owned it. I cannot stress enough, that without the help, advice and patience of the members of this board, not only would there still be a vibration in my car, but I may have taken a drastic step and parted with it. Thanks buickgsman for starting this thread, without which I might not have acted. Next year at the BPG Show and Go I'll buy you some malt beverages of your choice. Flyingbuick, I also owe you, (not just for this) anything I can ever do, let me know. Anyone else out there fighting the good fight, stick with it, you'll get it sorted; it just seems like you never will.
I've pretty much ran only the Dynomax mufflers going back to the late 80's. I did have drone on the shorter case Dynomax's on both of my 5.0's that had them. It happened right around cruising rpm (1800 - 2200 rpm). Above that and I didn't notice it and below was fine too. On my 71 GS455 I had the long case dynomax (along with the TA mandrel 2.5 kit) and no crossover. There was no drone on this system whatsoever. It was also very quiet. It was much quieter than the generic 15 year old "turbo mufflers" that were on it when I bought it.
Hi Robert, I'm glad your exhaust is all squared away. Mine is also much better except at idle I still have a slight but acceptable drone. Definately not as bad as with the flowmasters. One last thing I am going to try is a flexible pipe just off the headers to try and dampen the system. I like how quiet the car is with the dynomax mufflers, but I miss the wide open sound of the flowmasters. Someday I'll have the best of both worlds!!
Buickgsman After you get some hours on the new muffs they will burn out a bit and become a little louder and better sounding at wot. I am not a fan of adding some flex pipe. Before doing that I would try cutting some pipe between your x and one of your muffs so that your muffs are not the same distance from the x. Ford successfully did this different years on the Mustangs to eliminate drone. Also only rarely will that affect performance in any way. PS I like the Walker Ultra flows but prefer the big case long Magnaflows. All of last years winners of the engine masters challenge used Magnaflows. Check out Magnaflows website.
