Hey, I have been searching for a mercedes forum like this for awhile, i bought a 86 300e last year, good conidition around 200-300k on it. I already put 1400+ in it for new ac, everything, (live in south florida, gotta have it) replaced the ignition starter, neutral switch, got rims from tire rack, max tinted the windows, new headlights, but i want to do some mods to the engine, the car sounds supperr nice already, but maybe someone can point me out and see whats the best thing to increase hp on the engine that is somewhat cheap and easy, ill get some pictures up soon.

The M103 is pretty well tuned to begin with (for the 1980s). There's not that much that can be done to gain more than a handful of extra hp without spending $2k+.
Maybe you could fit a used rear diff with a shorter ratio to give a sportier feel at low speeds but I don't know how much the labour for this would cost.

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1989 300CE "Project HWA124"
(400rwhp Turbo Technics AMG C36 engine)

I think the 86' has the sportier of the diffs (in the US market)

Read some of the threads here to get an idea of what people are doing...

Probably looking at more than $2000 to get a significant gain.

The good news is you have one of the most solid engines ever built by mercedes and your tranny can hande almost double the output of the stock engine.

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-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Read PUMPISH's thread about modifying the M103 (with turbo).

There is no real cheap and easy way to add HP to this engine.

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Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon

Don't forget to put away some cash for the inevitable head gasket repair on the M103.