1971 250C fuel return question - Page 2 - Mercedes-Benz Forum

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post #11 of 19 (permalink) Old 03-30-2008, 10:54 AM
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Personally...

I would go with the stock set up. You would have to determine how much to "jet down" the T-fitting, and as you mentioned, always run the risk of starving out the carbs. Also, you would be causing a additional back pressure on the mechanical fuel pump.

Remember, your 71 is a different carb [vent valves, etc] than the carbs on the 72 which used the "constant orifice" method of fuel return. The later version was used in the U.S. due to emission control requirements.

JR

Last edited by E-Class Owner; 03-30-2008 at 11:01 AM.
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post #12 of 19 (permalink) Old 03-30-2008, 12:27 PM Thread Starter
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Thank you, I'll continue my search. Inside of my valve there were two parts, the pin that sticks out of the bottom and a small steel or lead ball that rests on the pin and pushes up against the bottom of the opening. Different than the picture on the previous page. Are there more part's? If that's all there is maybe I can melt the solder out and use my valve. Thank's Joe
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post #13 of 19 (permalink) Old 04-01-2008, 08:41 AM
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Well, I've exhausted my search, and cannot help, I'm afraid. The item is most definitely in the $200 range. Truth is, I haven't even seen one of those valves in several years, they were never very popular.

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post #14 of 19 (permalink) Old 04-01-2008, 08:45 AM
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Quote:
Originally Posted by E-Class Owner View Post
Are the current valves, #174 in the diagram, still factory crimped to make them non-repairable? I think the OP has two issues: 1) the price point on the new part, and 2) the issue of rebuild-ability, so to speak.

The needle/diaphragm insert for the older valves used to be available separately and at minimal cost; whereas, the newer [non rebuild-able] valves were pretty pricey considering the relatively simple nature of their construction and function.

Just curious...

JR
#175 - #179 in the pic are parts of the valve, which are available for rebuilding.

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post #15 of 19 (permalink) Old 04-01-2008, 07:05 PM Thread Starter
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Are there any other options? Is vapor lock a common problem without the valve not working? If I can't find a used one I must decide whether to pay $200.00 to repair old carbs or $850.00 for a weber conversion. Thanks again for any advice. Joe
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post #16 of 19 (permalink) Old 04-02-2008, 08:19 AM
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Do the math...

$200 vs. $850 for a carb conversion which will frankly devalue your car. The 250C is well on its way to being a specialty/collector car, as there were not all the many made and fewer still survive. Why mess the car up with an after-market carb conversion?

Unless you are really good at jetting carbs to get the engine running properly, you will most likely really regret the Weber move.

If the Zeniths are basically in good shape, and you have already done the remainder of the rebuild, including heli-coiling or drilling and re-tapping the stripped threads, then you are almost home free.

Spend the $200 and enjoy the car. I cannot answer your vapor lock question as I never drove any of my cars of that era with a non-operational fuel return valve; however, I sincerely doubt that DB would have included this feature if they did not consider it important to the overall functioning of the engine. Also, your profile does not indicate your location, so it makes it very difficult to speculate on this issue.


Good luck,

JR

Last edited by E-Class Owner; 04-02-2008 at 08:21 AM.
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post #17 of 19 (permalink) Old 04-03-2008, 07:23 PM
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Bag the Zenith's

While the 114 coupes are finally seeing some modest appreciation, IMO the market is still at a level where buyers appreciate performance and reliability over originality. And the Webers make a huge difference in drivablility. So my advice would be to bite the bullet and go for the kit. I say this because I probably spent double the cost of a conversion on the Zeniths on my three 250C's.

The other mod to consider is a Pertronix kit for the ignition.

If you decide to stick with the Zenith's, I suggest looking for a used carb that still has the valve with it.
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post #18 of 19 (permalink) Old 04-03-2008, 10:59 PM Thread Starter
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Thank 's for all the advice. I think I'll try to find a used valve and keep the Zenith's for now. If it look's like it's costing too much I guess I'll have to save up for the weber's.
Thank's Joe
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post #19 of 19 (permalink) Old 04-07-2008, 07:12 PM
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I did the Weber retro-fit on a previous 250C, and it really transformed the driving experience...depends on whether you're planning on actually driving the car and enjoying it, or trying to keep it original for some future investment value. Ctaylor738 is right on; personally, if my current 250C was in need of a carb job, I wouldn't think twice.

To get it running really well, there's a Mallory distributor (from a 70s Jaguar application I believe) that fits with minimal tweaking. I think my mechanic had to have some minor machine work done, which was the most expensive part.

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