Horrid exhaust note above 2,000 rpm

[jedwards]

Gentlemen,
My recently acquired early 250SL came to me with a brand new complete exhaust system.  It appears good quality, the correct size and pipe diameter  and well fitted. It is an OEM system rather than Mercedes original but I do not know the brand or any specifics. 
However above 2,000 rpm, the exhaust note turns rather sharp and unpleasant which detracts from the driving experience.
It sounds fantastic at idle and when cruising or when accelerating gently, but beyond 2,000 or 2,500 rpm, the exhaust note develops a “tearing calico” resonance that is harsh and unpleasant.

I would rather not have to remove the entire exhaust system completely and start  again, so am hoping others may have experienced a similar problem and could tell me which part I should consider replacing to solve this unfortunately resonance problem.

Jeff in sunny Western Australia

[Larry & Norma]

Is it a stainless steel system? I have heard they can change the exhaust note quite considerably
and can be unpleasant.

[jedwards]

No, it's a mild steel system by the look of it.
Jeff

[Garry]

Both my past owned 280SL and my current 230SL have had a loud rasping at around 2300 thru to 2800 rpm.  It is loud and quite noisy but it is also a sound that I really enjoy.  I don't think changing the exhaust system is going to change that very specific Pagoda sound at around 2500 rpm.

If you are cruising at around 60mph and the rpm is around 3250rpm the problem of a noisy exhaust is not there.

[Cees Klumper]

I have a full stainless system and it does not make any npleasant noise at any RPMs. You might look into replacing the end muffler?

[jedwards]

I sense that the raspy sound has something to do with the pressure waves from each exhaust stroke intersecting and setting up a resonance within the exhaust system.
I plan to check  the exhaust value clearances, cam and ignition timing to see if that has any impact. Following that, I thought the best and most economical approach may be to weld in a balance tube across the pipes between the resonator and muffler, as my straight 6 Aston Martin has.  This hopefully might disturb any beat resonance and could solve the problem.

My 250SL sounds nothing like our 250 sedan we had when I was young.
This is actually an embarrassingly nasty and unsophisticated noise, and certainly not what Mercedes would have wanted.
Jeff

[jedwards]

Problem  solved!

Upon removing the exhaust system it became clear that the apprentice had been  giving the job of welding up the new pipes. So he (or she) welded up the bottom half of the pipes that could be seen and left the tops of both pipes unwelded. The resulting leaks caused the awful noise.
Now properly welded, the exhaust sounds great!

Cheers