Hi guys , just wondering whats the consensus on the best place I should position the mufflers on my 57 BelAir? I want to avoid any 'drone' inside the car. I'm using 2" pipe with rams horns. Its just running a stock carburetted 350 ,nothing stunning...even has smog heads., and T350 Thanks in advance for any help, PB
move the mufflers to the rear as far as possible and make sure tips extend beyond the body. H pipe may help and dynamat on the wheel wells and in the trunk definitely will cut noise inside considerably
^^ interesting. I have 'Flowmaster style' mufflers. I say style because they are basically a knock-off copy I think
Run the pipes out the back past the bumper as was stated or out the side "PAST" the rear wheel opening as was done when it was stock. Pat
good post and valid question, i too will be designing my exhaust system for my 51 styleline with 350 sbc and smithy mufflers, i was wondering about not getting an annoying droning in the car, this has answered it, cheers Jason.
Drone comes from resonance or frequency. When the frequency hits the sweet spot you get drone. If you can stagger the lengths of pipes before and after the muffler on one Side vs the other that will help eliminate a sweet spot for drone. But that makes Things unsymmetrical under the car. That lack of symmetry fights the drone. Making one pipe thicker by adding a layer of pipe on the out side fights the drone by changing the resonance frequency of the pipe. H balance pipes help as do resonators. Confusing because their function is to Anti-resonate
Farthest to the rear as possible and exit outside the body , nothing within 30" of the engine , and slash cut tips help and do not point it at the ground unless its pointed away from the body , on summer only cars we have wrapped the mufflers with header wrap and it quiets down as part of the problems is from the vast flat sides which act like a drum skin and resonate the sound against the body and surface underneith it .
I used magnaflows, h pipe, in my 70 torino convert 351, heavy cam. Couldn't drive the car. Thought my head was going to implode. Went with super turbos and can even listen to the radio
My current O/T car developed a bad 'drone' after installing a dynomax muffer between the rear axle and rear bumper. It was right at my Interstate cruising speed of 70mph and was driving me crazy. I took my car to a respected local exhaust guru guy. He asked me what RPM the drone was at, and I told him right at 3000-3200rpm. He brought out a little foot long resonator from the back room of the muffler shop. He measured the exhaust system under the car and hand scratched some calculations. Then he put some marks on the piping near the rear of the drivers seat position, and said "we will put it here, and the drone will be gone". Sure enough the drone was totally eliminated and the overall exhaust sound didn't change a bit. He said he had done this for many folks over the years. He definitely had it figured out. The only downside was the resonator burned out after about 5 years, and had to be replaced to stop the drone. --- Steve ---
I always put the mufflers in front of the rear axle and run tailpipes out to the bumper. Never had any drone problems. Mufflers in front of the rear axle with short pies in front of rear tires or just pointing down can cause a droning problem. Mufflers way up front with long tailpipes can cause the "school bus" effect... Pipes rap going down a hill in gear just like a school bus. People get all hung up with the performance issue on a street driven car. They want 3" pipes for less back pressure but rarely get above 4500 RPM for any length of time where it could make a difference. Most people over think exhaust systems. Tail pipes make a difference.
My 63 BelAir has a complete Magnaflow exhaust system from the full length headers to the tips. Just a little too loud when you get after it. Draws a lot of attention. My 56 BelAir with full length Heddman headers, "H" pipe and 40 Series Flowmasters sound a lot better to me. Mufflers difficult to buy as you never know how they will sound until they are installed. By then its too late.
I've found it's both! Any free flowing muffler will have drone, regardless of where it's located. But a good crossflow will not have as much drone or resonance to the sound if it's located as farr back as possible, and exits out past the bumper. I'd also make a good divider panel between the trunk and interior, as most older cars don't have anything but a vapor barrier behind the back seat. A thin panel made from cheap Masonite, with sound deadener applied to one side will really reduce sound levels transferred to the driver. I have a later fold down rear seat in my '63 Falcon, and a barrier I built behind it. I could really hear the difference before and after I built the barrier. I can also hear the difference with the seat up or down, so it goes up if I want a quieter ride on a cruise.
Back when I was a kid, all we had was stock mufflers and glass packs and I don't remember much "drone" at that time, Ford had their mufflers behind the rear axle, Chevs and Mopars further forward under the seating area. First time I ran into drone was a 73 Pinto with a header and a Walker Royal Scot baffled grass pack. I figured the drone was caused by the dead even exhaust pulses and a cheap car with no sound deadening. I suspect that wrapping the muffler is a good way to cut down the resonance, but how about heat/sound baffles placed between the muffler and body? These were common on 30s-50s cars. I've never had a car with magnaflow or dynomax mufflers, but their design probably contributes a lot to the problem. (more than location) If one can't tolerate noise, they still make stock mufflers, don't they? LOL
I have seen different types of "heat shields" and understand they also work to, at least, deflect droning. Here is a shortcut to Summit listing: http://www.summitracing.com/parts/flo-51017/overview/
A great suggestion there and one we don't often think of. The trunks on a lot of our older cars are big echo chambers all too often. I agree 100% with the concept that the exhaust pipe tips have to exit behind the rear tires and as far back as you can get them along with being out past the body or bumper. One of my buddies hasn't yet got his head out of the 80's and is a big block super car nut. His idea of exhaust is hedders with turbos directly behind them and 3 inch pipes that turn down under the car in front of the rear axle. Riding in his car gives me just as big a headache now as it did 30 years ago.
Hey thanks guys!! lots of good stuff here!! I was thinking of putting the mufflers about under the rear seat ,with tailpipes out past the rear bumper . Wasn't too sure on whether i needed balance pipe or heat shield but it does make sense . Does the number of exhaust hanger brackets have any effect?
Put a substantial bend in the system somewhere. I did mine just after the mufflers. That fixed it. That tip came to me from a man that fights drone in diesel pickups.
I had a drone on an OT van that happened @ cruise between 65 and 75 MPH - right where I like to run. I got under it and tapped around with a wrench on the whole exhaust system and found one place that seemed to ring a lot more than other places. It was between the muffler and resonator. I took an old exhaust pipe clamp and a piece of rubber and put the clamp around that piece of rubber in the middle of that section of pipe. Gone.
Pretty much any chambered style muffler can give you the droneor resonation. Just drove our '47 Hudson 160 miles today and it has 2-chambered flowmasters with turndowns at the rear diff. Can't do tailpipes over the rear because of the sway bar. It has the resonance inside the car. To me it's not too obnoxious but it's definitely noticable. We can carry on a conversation without yelling. It did have tailpipes but they were under the diff. Couldn't change a tire because the rear wouldn't drop low enough to get the tire out of the wheelwell because of the tailpipes. It had no resonance with the tailpipes. All that to say I think alot of your answer relies on tailpipes.
WRONG!!!! Never had Drone in a car with mufflers mid body or even closer to the engine. A couple of ford friends about explode yer head with drone back in the day. we thought it was a ford thing. a friend of mine went to your school and his wife won't ride with him because of the drone. yup has mufflers in the rear go ahead and do it your way my cars don't drone!!!
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