W126 420 sel exhaust options - PeachParts Mercedes-Benz Forum

macdoe · #1 08-20-2011, 02:26 AM

Would there be an alternative to this exhaust that Mercedes has put onto my 1988 420 sel ? I really despise the pipe that goes behind the engine and right up tight to the firewall. This pipe definately hinders the access to the bellhousing bolts. We are swapping a running engine in place of the non running engine the car came with and I would rather not put this exhaust back on. I was wondering if there is another engine that came with a more reasonable set up that we could swap in place of the factory design ? I am looking for maybe something like dual exhaust. Also wondering if the exhaust on this car could be converted to just run with a regular single muffler per side instead of the four muffler design....or is this exhaust designed this way for a reason? Thanks.

macdoe · #2 08-20-2011, 03:54 PM

hi

Hit Man X · #3 08-21-2011, 04:59 PM

Quote:

Originally Posted by macdoe

Would there be an alternative to this exhaust that Mercedes has put onto my 1988 420 sel ? I really despise the pipe that goes behind the engine and right up tight to the firewall. This pipe definately hinders the access to the bellhousing bolts. We are swapping a running engine in place of the non running engine the car came with and I would rather not put this exhaust back on. I was wondering if there is another engine that came with a more reasonable set up that we could swap in place of the factory design ? I am looking for maybe something like dual exhaust. Also wondering if the exhaust on this car could be converted to just run with a regular single muffler per side instead of the four muffler design....or is this exhaust designed this way for a reason? Thanks.

Just score a pair of 380 Euro dual manifolds/downpipes and off you go. I have a set from a 500SEL Euro going on my US 560SEL.

It is pretty well known that the US exhaust systems are nothing short of crap. Sure the Euro logs are not as great as the four piece set, but they sure are a ton better than the US nonsense.

Oh, scrap the factory dual cat assy and pocket some cash too or sell it to someone in CA that needs a good factory system. Big center cats here are fetching $200-250 in scrap alone. If you need a cat, this should be the PN for the dual in/dual out with O2 sensor for your car - 94038.

http://www.magnaflow.com/02catalytic_converters/02product/displayuniversal.asp?universal=94038

Not sure what 420SEL you have, but the one I had just had three mufflers... one out the back (dual in/dual out) and the two 'kidney' resonators under the rear seat. The rear muffler is straight through, the resonator off my 300SEL was too... so I will assume the resonators on the V8s are also.

Basically the catback is fine, the cats to the heads are what are terrible. Expect a boost in power and maybe fuel economy too.

macdoe · #4 08-27-2011, 03:39 PM

Thanks, I wonder how a person might come across some euro manifolds? Do the 560 manifolds fit the 420, since the engine is similar?

Does the 4.2L and 5.6L share the same block and heads and it is just the bore and stroke that are increased to make the 5.6L?

I wonder if there are any European members on this, the tech side of the forum? I am normally on the diesel side and there are members from Europe over there I could perhaps ask, but this side would be more familiar.

My brother and I are fixing this for Dad since his Chevy is falling apart and we got it for cheap since the chain tensioner failed and the timing skipped. I think that if we can find some euro manifolds we will just run dual exhaust straight through some glass packs and out, if back pressure is not an issue. I have the flanges off the single exit manifolds from two engines so we could just use those and have new pipes bent from the manifolds back to the glass packs and out some nice cheap tips.

Hit Man X · #5 08-27-2011, 05:15 PM

Well in the height of the 'Grey Market' era in the mid 1980s, MANY 380SE/L and 500SE/L were brought into the US. Even today I can search the want ads, at least in Texas, and find these vehicles if I search hard.

So I would just keep looking around and you will find a pair eventually. Or start sniffing around on ebay, someone is bound to sell some there and have no idea what the hell they have listed.

http://timevalve.com/cat/euro/p26b.html

I have all that stuff to install on my 560SEL. I picked up the downpipes in the junkyard years back. I just need to attain a high flow dual in/dual out cat with integral O2 bung and a few mandrel bends to connect the downpipes to the cat assy.

Without some research I cannot say if the blocks are the same, I seriously doubt it. To increase displacement that much, just flat out requires a taller deck with a larger bore. I remember the 5.0 and 5.6 are the same block for some reason.

Think of it this way... 302 Ford and 351W. Very similar but very different. Taller decks by over 1", larger headbolts, longer rods, larger rod bolts, totally different piston compression height, different oil pans, different intake manifolds, etc, etc, etc.

The stock mufflers flow well for what they are on these cars, these are not Volvos where the car cannot breathe. When the system fell apart on my 300SEL (PO and all their city driving), I cut open the stuff to have a look (it looked simply like a Magnaflow internally...). Just the catalyst assemblies flow like ass... just like the '80s BMWs.

The great news? You can scrap these old catalysts and make a bundle, I received right around $250 for the one off my 735i... and your 420SEL has two! One huge main cat and that precat that is the size of a normal unit.

Hope it helps and keep us posted.