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#1
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Getting Ready for the Road.
Just bought the car, going to do an all around maintenance on a 1971 250C.
But I have questions.. spark plug recommendations? Your favorite with part number if possible. Oil Recommendations: I know.. opening can of worms. I used Castrol GTX racing oil in my 928S because of the high zinc levels. I had 15-40 recommended as a weight from the previous owner in Colorado. I live in Rockford Illinois about an hour and a half NW of Chicago. The car has some strange looking plug wires, pic below. Bosch Brand. I looked at them in the dark and they are not sparking on the outside, but I am getting a random miss when hot, replace? Problems with the Zenith Carbs also, so it may have little to do with ignition. Getting coolant out of the water pump weep hole, so that has to go, will replace all belts along the way. All replies are much appreciated Sirs! Gary |
#2
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Pertronix is always a good idea. Not sure if you car has the ignition amplifier but it bypasses all that.
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Tony H W111 280SE 3.5 Coupe Manual transmission Past cars: Porsche 914 2.0 '64 Jaguar XKE Roadster '57 Oval Window VW '71 Toyota Hilux Pickup Truck-Dad bought new '73 Toyota Celica GT |
#3
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Those look like the original plug wires, at least at the plug end. I’m pretty sure I used a Crane Cams ignition conversion in the 250C but it could have been a Pertronix. Either way, it did run better after the conversion. The 250/8 had points controlling an electronic ignition which worked ok until the points developed a non conductive film. The ex was not happy when the car died on the way to work.
Michael |
#4
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Pertronix
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There is a black box on the drivers' inner fender with a red light on it, is that the amplifier? So the amplifier is good or bad? |
#5
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Electronic Ignition
So, the vote around here in favor of the Electronic Ignition? Is anyone still
running points ignition? My Current MB Guru is Pierre Hedary and he seems to think that most of the problems with points ignition system stem from cheaply manufactured condensers and that worn distributor bushings cause problems with EI. But his big complaint is that making the switch takes the grunt out of the engines' performance. The last points ignition I used were on British Cars and they seemed to do ok as long as I did not leave them on and not running for extended periods of time. Other than that I have no opinion, but yours is very important to me! Also, I am putting together an order and I want to buy plugs, please tell me what you use even if they are not special. If those plug wires are original, shouldn't I change them? I am in the habit of doing that about every 5 years on my US Made vehicles.. Thanks.. G Last edited by glmoore0001; 09-17-2021 at 05:46 AM. |
#6
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I’m not sure when Mercedes started using the electronic amplifier with points. My ‘68 250/8 had it. The problem was that since the points were switching low voltage and current, they lost some of the “self cleaning” action that just a bit of sparking provides. They required an occasional cleaning with a business card to keep the ignition in top shape.
I went optoelectronic in the 250C and either the 280C or 450SEL. I may have done it partly due to marketing but did like the results. The 250C started instantly and seemed to run better right after the install where idle had been a bit rough before. I think the original amplifier was in an aluminum housing, you mention a black box with a red light. That sounds like an aftermarket unit. Do you still have points? It might be a points driven CD ignition or an ignition amplifier. If you have a shutter and optical pickup, it’s probable either a Crane or Pertronix. Michael |
#7
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Quote:
__________________
1971 MB 250C 2001 Dodge Ram 2500 Diesel Rust Free and Reliable 1977 HD FLH Solo with tractor seat and pogo |
#8
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Regarding plugs, if you search this forum you'll find lots of advice that can be summarized to...
- WDC7 Plugs unless you need WDC6. - No R in the plugs, unless it says "R0"; you do not want resistor plugs. - No fancy metals, just basic copper plugs. Not platinum, iridium, fancy forks or anything else. - There is a spec published for total resistance of the wire and the boots. Check it to know if your wires are any good. A look at the scope pattern at 4,500 and idle is also a good idea. - The timing would be set at 4,500 rpm, plugging vacuum lines to the distributor and then checked at various RPMs. Also check the dwell at various speeds to ensure that it doesn't change more than like 2 or 3 degrees from idle to that high rpm. -CTH PS. Get the ignition to spec before worrying too much about the carbs. When you deal with the carbs, the book says you want more than half a tank of gas in there. Make sure your tank strainer is clean. |
#9
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Quote:
And the vacuum to the distributor has no vacuum hose going to it, wide open. Should there be one or should that connection be plugged? If running a Electronic Ignition should I still plug that connector when checking timing? Thanks.. Gary
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1971 MB 250C 2001 Dodge Ram 2500 Diesel Rust Free and Reliable 1977 HD FLH Solo with tractor seat and pogo Last edited by glmoore0001; 09-28-2021 at 10:58 AM. |
#10
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I used the XR700 on one or both of my conversions. It worked fine for me.
As for plugging the vacuum line, normally there would be a line from a ported vacuum source which may or may not have vacuum on it at idle. You pull it at the distributor to remove any advance it may be inducing and plug the hose to eliminate the vacuum leak created by pulling it off. It may be that a PO did away with vacuum advance altogether. In the bowl of the distributor, under the points/pick up, there are some weights and springs. This is the mechanical advance. As engine speed increases, the spark needs to happen earlier. Centrifugal force pulls the weights out which causes the part of the distributor shaft with the lobes on it to rotate. That changes the timing of the spark. By running the engine at 4500 rpm, the mechanical with be “all in”. Setting the timing this way may leave you with the timing off at idle but should give you what the engine wants. Because you have an optical pickup, you won’t have a dwell adjustment. By adjusting how open the points are at the tip of a lobe, you vary the ratio of open and close. It’s important to give the coil time to do its thing, dwell is this time. I don’t remember if the XR700 changed the dwell based on rpm, some aftermarket ignitions do, some don’t. Michael |
#11
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__________________
Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033 Current have, 1983 300SD 126.120 |
#12
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Thank you for the information Michael!
__________________
1971 MB 250C 2001 Dodge Ram 2500 Diesel Rust Free and Reliable 1977 HD FLH Solo with tractor seat and pogo |
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