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1981 300TD 360k--1966 230 165k--1970 280se 172k
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Discussion Starter #1 (Edited)
Before I figure out what's wrong with my carburetors, I want to be sure the ignition is up to snuff. 1966 230 with the 180.945 engine. I see the timing spec in the owners manual says "approx. 2 degrees UDC." However, the service manual has an assembly setting stating "Stroboscope check at starter speed and with spark plugs installed 3 degrees BTDC". Then there is also a table for "Ignition setting and stroboscope values at engine speed" and lists a range of degrees at various RPMs. The text says to check it at 4500 RPM without vacuum. That setting is listed as 37 degrees.

First of all, is UDC the same as BTDC?

Secondly, is there really 37 degrees of advance at 4500 PRM? Seems like a lot. What do you guys recommend? Just set it at 2-3 degrees BTDC at starter speed and then check it at 4500 RPM?

Also, is the table with "Closure angle" the same as dwell?

Forgive me, I am more familiar with diesels and it's been many years since I tuned up a gasser. What's more important, dwell or gap? Doesn't one affect the other?
 

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UDC is BTDC in German. 3 BTDC at idle is fine. All in timing is 37 BTDC @4500 RPM. Max RPM is 6200 RPM but the engine will live happily above that. Use proper plug leads and terminals not silicone carbon string leads and get rid of the points . use a pertronix ignitor .
 

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1981 300TD 360k--1966 230 165k--1970 280se 172k
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Discussion Starter #4
I wanted to rotate the distributor to bring it to the middle of the adjusting plate range at TDC following the tutorial found on the Ponton site. It said to rotate the helical cut shaft a gear or two, but my distributor shaft had tangs below the helical gears that would only allow a 180 degree rotation. So I had to settle with the maximum advance on the adjusting plate which left me at exactly 3 degrees BTDC at idle speed.

The car is still a bear to start. I thought I had it fixed after checking plug gaps, setting dwell, setting RPMs, fixing a possibly leaking vacuum connection at the carb, adjusting idle mixture, and balancing the carbs using the #3 and #4 plug pull-off method. The car starts perfectly when warm, but takes many cranks to start cold, using every combination of choke and pedal.

How much effect do the bi-metal spring diverting plates below the carbs have on cold starts? My springs are shot.
 

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73 280SE 4.5, 71 300SEL, 03 BMW Z4, 72 Fiat 850, 80 Triumph TR7, 85 Porsche 911
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A while back, I posted some stuff for the zenith carbs, to the online resources portion of the forum... I might have other stuff too if you're still in need.
 

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1981 300TD 360k--1966 230 165k--1970 280se 172k
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647 Posts
Discussion Starter #6
Thanks for the offer, Grubeguy, but my carbs are Solex 38PDSI. I have searched high and low for an exploded drawing and have come up empty. It seems they were only used for two years (1966 and 1967) and only on two models (230 and 250). I would like to tear them down but would feel more comfortable with a drawing.

The PAITA carbs, by their looks, appear to have some slight differences. Still, I hesitate to use the drawings and specs. You know how it is with these maniacal devices: one little thing being off and you're buggered.
 

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1965 220S, 1999 Volvo V70 (wagon), 2006 Ford Crown Vic Police Interceptor, 72 350SL 4 Speed
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I thought the 230 and 230S of that era used ZENITH INAT's. I had a 67 230S with the ZENITH's. The later 220S, 250S and 280S all used the ZENITH's. (Just a comment)
 

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1981 300TD 360k--1966 230 165k--1970 280se 172k
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Discussion Starter #10
I owe you one, Grubeguy. That PDF was very helpful. I'll run through the adjustment procedures and report back. A poster over on another forum suggested that there may be a vacuum leak in the fuel lines from the tank to the pump allowing the fuel to run back to the tank when the car sits. I'll check that out, as well.

Thanks everyone for your replies. I'm also dealing with the brakes and heater cores and am rushing to take advantage of the weather. Heater cores are out and at the radiator shop for a boil and leak test.

I also pulled the shoes on the side that had the misaligned or mis-sized shoe. The radius of both shoes were the same. When I put them back on, the radical angle of the slave piston on the front shoe mysteriously disappeared. So I'm going with that.

I realized that you can't power bleed the rear brakes because of the compensating/check valve at the master cylinder. Have to buy more brake fluid and get my helper to pump the brakes.
 

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1993 MB 500E, 1965 MB 220b
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77 Posts
bi-metal spring diverting plates below the carbs

How much effect do the bi-metal spring diverting plates below the carbs have on cold starts? My springs are shot.
This mechanism could be affecting your starts to a certain degree...

Check to see if the plates on your car are frozen in position (grab the counter weight that the diverter plate shaft is attached to & try to roatate it). This mechanism is often neglected or not even known to exist by many owners. When cold, the plates are in the closed position. The purpose is to allow warmer air/gas to circulate about the base of the carb/intake area...assisting in cold starts & initial warming up conditions. As exhaust manifold/engine compartment temperatures increase, the bi-metal spring elements expand; rotating the plates to the open position allowing exhaust gases to escape directly thru the exhaust pipe.

The shafts of these diverting plate mechanisms will lockup if not maintained (they are subject to the incessant abuses of heat, weather, time & oxidation). If frozen open, the car could possibly be harder to start in colder conditions. If frozen shut, the base of your carbs & intake air will be subject to higher operating temps & exhaust will be restricted to some degree; resulting in rough idle & operation.

What I have done in the past is first liberally blast the rotating shaft surfaces with a penetrant like PB Blaster. You may have to use channel lock pliers to grasp & rotate the counter weight. Work it easily, don't force it. Once free, give it time to dry out before liberally applying a graphite-based lubricant to the rotating surfaces. Check & lube once a year & you won't have any future problem with it.

Since I'm a 3 season driver rarely running in truly Cold temps, i removed & stored the bi-metal springs & wired my diverter plates open using stainless steel wire to hold the counterweights in place for restriction-free flow.
 

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1981 300TD 360k--1966 230 165k--1970 280se 172k
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Discussion Starter #12
Thanks for the info, Der Furor. My plates rotate fine--the springs are broken. How do you determine the position of the plates if I want to wire them shut? Is the plane of the plate the same as the slot in the shaft? That would make horizontal the closed position, right?

The car still starts hard after adjusting/balancing the carbs and corrected timing/dwell. I've been driving it as much as I can to see how it performs, and the other day after parking for a few minutes, it took 20 minutes to get it going again. Usually it is fine when it is warm, so that is something new. Sometimes it seems like a fuel problem and sometimes it seems like ignition. Once the car gets running and warm it is perfectly fine.

So I'm going back to square one. Check tank strainer, replace soft lines, inspect/rebuild/replace fuel pump. I may just bite the bullet and put in a Petronix system with their upgraded coil.

I have a question about the fuel pump. It appears there is some confusion about the type I see available online. A couple of posts referred to a lever-type and a push-type. The ones online appear to be the push type and I'm betting that my original is the lever type. Someone suggested a tapered gasket or somesuch to make the push type work. Was that a legitimate workaround? Or can I just find a new or rebuilt fuel pump (or a kit) that is a bolt on?
 

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1993 MB 500E, 1965 MB 220b
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Plate Position

How do you determine the position of the plates if I want to wire them shut?
With the shafts freely moving & the bi-metal springs removed, gravity will turn the counterweights to the normally closed position. You do not want to wire them shut (your car will run like crap once it warms up). The wiring would be done only to keep the plates open (i.e. holding the counterweights against gravity).

Your fuel pump may also play a part in the hard cold starts. The original-style mechanical fuel pump has a hand-primer lever which would allow you to prime the fuel system if the car had been setting long. Some aftermarket replacement pumps do not include this feature (I've had one of these before). As a result, if the car has sat for an extended period of time, for several possible reasons there may not be sufficient fuel within the carbs & supply line to start & keep the car running until the mechanical pump can deliver the required uninterrupted amount (this is a reason why you must keep cranking the car to finally get it started).

If your current pump does have the priming mechanism, pump it 10-12 times prior to starting the car. If you have the original pump, but it isn't working, it is worth getting a rebuild kit for it (the original lever-type is the better design).

If your pump has a screw-on lid, undo it & drain any water which may be present.

Coupes & later model sedans were outfitted with electric fuel pumps (which are fine as long as they keep getting electricity).

If you don't have a hand-priming pump, try this test next time you go for a drive & have a hard start (or hard restart). Take a squeeze bottle with a little bit of gasoline in it. Have your air cover off so you have access to the top of your carb(s). Squirt some gas down into your carb (this somewhat imitates the priming function). Turn the key. Does the car start right up? Does it keep running or die out? If it dies out, how many times do you have to squirt gas in the carbs before the car starts & runs normally? (This will be the approximate volume of fuel which is not but should be within the fuel line between the fuel pump & carbs for startup).
 
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