To All,

Has anyone been able to fit a downstream cat converter on a '74 M110 4-barrel 280S? My mother-in-law is fighting this problem in Los Angeles, and I've heard the original cats that bolted to the exhaust ports are no longer in stock.

One of these cats is leaking, fumes and heat are in the engine bay and wiring is getting cooked.. The car won't pass smog until this gets resolved-- does anyone have any ideas?

Thanks,
Nate Stanley
1979 300D 211K and still going

Nate,
You have a 'Thermal Reactor' bolted to the exhaust ports. It's possible to replace the Thermal Reactor with a regular exhaust manifold and get an aftermarket cat installed downstream someplace.
The question is - will California Smog / Inspection regulations allow a downstream cat to substitute for the Thermal Reactor currently fastened to the exhaust ports. Also remember that if the car has an Air Injection system and an Exhaust Gas Recirculation system connected to the current Thermal Reactor / exhaust arrangement, they will have to be connected to whatever manifold / converter you install to be 'legal'.
By the way, a 1974 is 27 years old.
Can it be registered as "Antique' or otherwise exempt since it is 25 years or older? Maybe you can run without installing a cat.
Good Luck,
Mark

Nate, check in to whether or not your 74 is exempted from smog check. My 73 is exempted, and was 2 years ago when I bought it. Not sure if the cut off is by model year or 25 years of age.

Mike & Mark,
Thanks for helping--
For the record, the car's registration renewal came with a requirement to smog the car. Seems like the State still thinks the car has to be smogged, so how does one persuade them otherwise in view of the 25 yr exemption. Any suggestions?

Nate

Nate,
I checked the California Air Resourses Board Website for the most recent ( 2000 ) regulations.
Unfortunately, only vehicles prior to
1974 model year are currently exempt from Smog Check. So the next question is - will a substitute converter with all the required air injection and EGR plumbing be allowed by your local smog inspector?
I took an emmisions repair course as part of my job, several years ago.
The instructor showed me a catalog from a California company that specialized in emmisions parts for older cars, including Mercedes. I don't know if they are still in operation. There are also several new and used Mercedes parts sources around the US
Good Luck,
Mark

Mark,
thanks for the advice-- Would you know the name of the company?
Please advise,
Nate

Nate,
I looked through 2 boxes of papers and couldn't find it. (Of course, 6 months from now, it'll turn up when I'm looking for something else!)
I did find this on a websearch -
ECONOMY SMOG PARTS
1-800-232-7670
smogparts@smogfree.com
"Parts 1966 to Current...Mercedes...
Thermal Reactors"
It sounds like the outfit I remember but that was 8 or 9 years ago and I've never had any dealings with them.
Good Luck,
Mark DiSilvestro