Performance upgrades for 71 250? - PeachParts Mercedes-Benz Forum

#1 03-08-2003, 07:34 PM

I'm pickin up a 71 250 next week, PERFECT shape, been garaged all its life, only a few dings, perfect interior, for only $1000! well anyways, I'm a chevy man, so I'm all about performance. So what can be done to these engines?

Mark DiSilvestro · #2 03-09-2003, 02:05 AM

Convert to Weber carbs and a manual shift!

Happy Motoring, Mark

rbmercedes · #3 03-09-2003, 09:28 AM

My mech swears by the Pertronix ignition upgrade, as well as the Weber conversion.

Happy Motoring

RBM

#4 03-09-2003, 05:02 PM

Aight good lookin out. Got any links or recomendations of places to get this stuff? BTW could any modifications to the exhaust system be done? Also its 71 so I ain't gotta worry about smog lol. Since I'm practically stealing this car for $1000 and its in perfect shape I wouldn't feel bad about dumpin in another $1000...

gmask · #5 03-09-2003, 06:53 PM

http://jameng.com/ <-Webers

http://www.durranceeng.com/ <- This guy does
Petronix conversions and distributor tuning.

http://timevalve.com/cat/us/p08b.html You should beable to put a dual line exhaust system in as an improvement.. many 250's came with a dual inlet / single outlet system. http://timevalve.com/cat/us/p06b.html

ctaylor738 · #6 03-09-2003, 07:00 PM

You can look at jameng.com for the Weber conversion, and pertronix.com for the ignition upgrade.

When you upgrade the ignition, get rid of the rat's nest of vacuum controls in favor of straight vacuum advance. Have someone check your advance curve.

Make sure that your throttle bushings are in good shape and that you are getting full carb opening with the pedal to the metal.

Agree on the manual conversion - the automatics are terrible power eaters.

#7 03-10-2003, 01:44 AM

No one in this thread has mentioned the installation of a performance cam like they do in American cars! Is this not possible, or does the overhead cam rocker arm design limit this consideration? Does anyone make a performance cam for an older Mercedes 6 cylinder engine?

Mark DiSilvestro · #8 03-10-2003, 02:15 AM

These particular single-cam sixes were never a popular competition engine and the newest of these is now 31 years old so there's not much 'tuner' hardware availible. Outside of what's already been mentioned here, most performance mods would have to be custom made.

I should add that my '72 250 originally had a dual exhaust system straight through to twin tailpipes, but most suppliers have superceded that to a 'dual into single' system. I noticed a bit of power loss when I fitted such a replacement exhaust. (But, strangely, my auto trans started shifting better!) Finding or fabricating the original dual type exhaust system might add a bit more power.

There's a guy, with a Mercedes shop in North Carolina, that vintage-races a 250SL. Maybe he knows some other soup-up tricks that could apply to one of these engines.

Happy Motoring, Mark

wbain5280 · #9 03-10-2003, 07:47 AM

You could add NOS and then it would go really fast. If not that, how about a modern day fuel injection system? You would have to find a set of FI manifolds off a 6 cyl SE/SEL but you could do it.

Mark DiSilvestro · #10 03-10-2003, 10:56 AM

But didn't those 6 cyl. SE/SEL have MECHANICAL fuel injection? you would need the whole SE/SEL engine block to mount the fuel injection pump.
There was a 250E version of the M114, sold outside the US. It had Bosch electronic fuel injection similar to that on the early 3.5/4.5 V8s. I saw a Texas 250CE parts car on Ebay last year. That injection might make a more likely transplant if you could find one.

Happy Motoring, Mark

wbain5280 · #11 03-10-2003, 01:09 PM

Those 250/8's never had mechanical FI or any other kind of FI here in the states. The 250CE engine would be a perfect fit. I suggested the manifolds from the SE/SEL since they would fit and electronic injectors could be made to fit, drill some holes in the proper places away you go. Sorry, I've been reading www.engrish.com for a while.

Mark DiSilvestro · #12 03-10-2003, 02:18 PM

Well, after checking out that 'www.engrish.com' website I was thinking.... Maybe a Datsun 280Z engine and 5 speed could soup-up that 250!

Happy Motoring, Mark

wbain5280 · #13 03-10-2003, 05:41 PM

Mark, it would be less work to put in a 280SE engine. A newer 5 spd trans could be found. Perhaps even a newer 300E engine would be better. No V-8's though, not really enough room.

Mark DiSilvestro · #14 03-10-2003, 07:14 PM

Yeah, I wish someone could come up with a, relatively easy, 5 speed conversion for these cars, maybe a ZF or Getrag out of a BMW. The factory Mercedes 5 speeds are about as common in the US as snow in Miami. I never had much complaint with my '72 250 engine but my automatic is a real 'slushbox'! I do have a 4 speed manual box, probably out of a 240D, that I picked up for free at Carlisle Pa. One of the flea market vendors packed up and pulled out, leaving the tranny near a trash can. But I still don't have the rest of the conversion bits, shifter, clutch pedal and especially a matching clutch-flywheel to fit my M130-2.8 engine.
My 250 has been parked for awhile as I now prefer driving my manual-shift 220S, even with the '4 on the column'.

Happy Motoring, Mark

240 Ed · #15 03-13-2003, 09:43 PM

There is not much reason to soup up this engine, it is the transmission which is the down fall.

And NO, not because it is an automatic! Actually these autos were direct-drive to the rear, because they did NOT use a torque converter. Instead they use a fluid coupling. This allows the engine to idle and not stall when the car is stopped. Once under way, the drive is direct, like a stick!

The reason I say the engine is okay, and the trans is the downfall isn't really true either, but the rear end gearing is something like 4.10 -1, which are "drag" gearing.
IOW, it really spins the engine, and you get a lot of acceleration out of this small engine.

I think you will be satisfied with the performance once you start driving it, the car doesn't really encourage hard acceleration...IMHO...