rough running

nealf

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Hi I am puzzled by a rough (when car is warmed up) issue on my 2800. Car runs great when cold but after it's warm it burps and stutters and stumbles while rowing thru the gears.

I have adjusted and readjusted the points
I adjusted, retarded and advanced the timing

and still the issue. I don't think its carb related I think it may be ignition related.

I have a replacement set of points on the car as the old set broke. the dizzy is not stock.

can points/rotor/cap act funny once car is warm and metal expands?

any help appreciated thanks.

nf
'70 2800CS
'72 Tii
 

Stevehose

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Sounds like your carbs may be running rich when hot? Engines like rich mixture when cold, then will be too rich for smooth running after it warms up. Did this suddenly start behaving like this?
 

nealf

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fuel filter under hood? seems clean, Can't recall the last change.

this just started happening after the points were replaced back in may. not much driving from june until very recently so I am driving it a lot now and it's acting up. the webers were rebuilt several years ago I wonder if that is the issue.

I have had issues like the current ones and it was ALWAYS ignition related that is why I am asking that first.
 

dang

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When it stumbles, is it all the time, only under acceleration, only while steady speed?
 
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nealf

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thought previous stumbling was under light acceleration load not heavy pedal mashing but it's both and starts to breakup about 3500rpm...
 

Stevehose

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Time to ditch the points and get a Pertronix or the Mac Daddy of all ignition upgrades, the 123Ignition distributor. If Pertronix you can disconnect the wire to the condenser but keep it mounted for a stock appearance.
 

dang

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I've always used stock ignition and have never had any major issues. The only car I had to troubleshoot ended up being the Pertronix ignition pickup that was already on the car (2002).
 

Ohmess

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If the car sat through July and August and two weeks into September, you may have some deposition inside the carbs from fuel evaporation. You may want to run some fuel system cleaner through the car. I like Liquid Moly, but there are a bunch of them out there.
 

lloyd

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Hi I am puzzled by a rough (when car is warmed up) issue on my 2800. Car runs great when cold but after it's warm it burps and stutters and stumbles while rowing thru the gears.

I have adjusted and readjusted the points
I adjusted, retarded and advanced the timing

and still the issue. I don't think its carb related I think it may be ignition related.

I have a replacement set of points on the car as the old set broke. the dizzy is not stock.

can points/rotor/cap act funny once car is warm and metal expands?

any help appreciated thanks.

nf
'70 2800CS
'72 Tii
Food for thought?


Although your ignition points setting can affect your ignition timing, I doubt your problem lies there. You describe the symptoms as only occurring when the engine has reached normal operating temperature. In other words, when the engine is kalt, it runs "acceptably." Ignition points are typically not cold/heat sensitive. An ignition coil or the ballast typically connected to some coils can act up when hot - so those are things to consider and possibly eliminate as problem sources. Since you are employing an aftermarket distributor, is the coil stock or aftermarket? The presence of the aftermarket distributor leads one to wonder if it was intended to boost the available secondary voltage (to the spark plugs) allowing very large plug gaps to fire the leanest mixtures. If your spark plug gaps are much wider than normal - this may “test” a weak ignition system and lead to misfiring, especially with a lean fuel mixture.

There are other things on your engine that are (or should be) temperature sensitive, namely, the carburetor chokes (- unless they are manually operated). Choke flaps are typically engaged, as are the fast idle cams - holding the throttle plates slightly open, when the engine is cold. Is it possible that after your engine heats up - your chokes are still engaged? This, as Steve, pointed out, will result in a very rich fuel mixture. Conversely, your chokes may be providing a rich mixture when the engine is cold, but if there is a problem only when the chokes are disengaged - this suggests the carburetors are feeding the engine an unacceptably lean mixture. An unacceptably "lean" mixture can be caused by (wait for it) . . . a vacuum leak. It does not appear that your aftermarket distributor is equipped with a vacuum operated advance, so we can assume you did not inadvertently disconnect what is not present. However, are all disconnected vacuum ports properly sealed? Do your manifolds or carburetors share a balance vacuum line? Of course, there are other vacuum connections you might consider checking.

Your aftermarket distributor may also be related to your symptoms. (But maybe not.) One wonders what was wrong with the original distributor - and why, when you tried reinstalling the original distributor, the engine ran “terribly.” The purported advantage of the aftermarket distributor over the original is ball bearing construction allowing for better spark control at higher revs and what appears to be a more precise means of controlling ignition advance. I wondered whether the points base plate was designed to handle two sets of points, and yours may be missing one set. It should function on one set of points, but obviously, if you are looking for greater dwell/coil saturation time that, is one of the major purposes for the dual points setup. It appears that you are able to “dial” in ignition timing, as indicated by the markings around the distributor base. But are there simple adjustments to alter the weights and springs to alter the centrifugal advance? Perhaps something there is amiss? The aftermarket distributor also has a condenser. A failing condenser can mimic a failing fuel pump, but your description of the problem does not suggest this, or does it?








 
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DWMBMW

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Many years ago I had a Mallory dual point distributor and an MSD coil that I was never able to get working properly (probably me not the equipment) so I went back to the stock Bosch for a long time and thought it was fine until I installed a 123 unit. It made such a noticeable difference in overall performance, smoothness and fuel mileage that I can’t image ever going back to stock for a coupe that you want to drive.
 

nealf

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hmmm...thanks for the recent replies and help. With my limited knowledge I will try some troubleshooting.

and yes, it's a dual point distributor. I always ran a single set and on the way home from The Vintage in May, the previous set of points that had been in the car forever and had been reliable and smooth running, broke. The spare set I carry was installed and the car ran differently and still suffers today. I used a point file yesterday to try to smooth any high spots and then regapped and still the same thing. great running out of the garage, and then sputter and popping after car is warm. I have another set of points, cap, and rotor hopefully coming from the Roto Faze shop but that has been painstakingly slow as the original and only guy who built this stuff is 83 and suffering from a host of medical issues and is relying on his nephew to sort out the business..
 
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dang

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The spare set I carry was installed and the car ran differently and still suffers today
This should've been said first thing. Sounds like you know what needs to be looked at... :)
 

nealf

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Sorry! I didn't think there would be that much, if any variation in the spare set of points and still don't know. The points are supposed to be robust enough that they would not suffer after car warm up like someone mentioned above.
 

dang

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Troubleshooting always starts with reviewing if anything has changed prior to the problem occurring. Changing points and immediately having an issue would seem fairly convincing that the points are part of the problem. If you back up one more step you can make sure something obvious didn't break the original points, but that all you can do.
 
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zinz

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Car runs great when cold but after it's warm it burps and stutters and stumbles while rowing thru the gears.
Feel the coil once the car is warmed up and displaying the bad running characteristics... Is the coil too hot to touch? (LLoyd also mentions this)

Did you also replace the condenser?

Ed
 

zinz

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They don't make points like they used to - mostly junk now.
This is not just internet opinion... today's points are not nearly as good as what was previously available. Another thing that is becoming long-forgotten is that points and condenser resistance values can be different and act against one another. Here's a explanation from the web:

"Contact pitting results from an out of balance condition in the system which causes the transfer of tungsten from one point to the other so that a tip builds up on one point and a pit on the other. The direction in which the tungsten is transferred gives an indication for correcting the situation. If the tungsten transfers from the negative to the positive point one or two corrections may be made. Increase the capacity of the condenser, shorten the condenser lead, separate high and low tension leads between the coil and distributor, move these leads closer to the engine block. If the transfer is from the positive to negative point, reduce condenser capacity, move low and high leads closer together and/or away from the engine block, or lengthen condenser lead. "

...I asked about the condenser; if it is failing, it could be adding too much resistance. Resistance builds heat, and once ignition parts get overheated, they display poor running characteristics as you are experiencing.

Hope you find the problem.

Ed
 

nealf

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I am self employed so I just took the car out for a shakedown run. Sprayed some car cleaner on the carbs just because I wanted to make sure they weren’t gunked up. Again running great at first and started to break up and sputter when warm but not as bad as last night. Coil was warm but not overly hot to touch. This is the carb position on cold engine and once chokes were off when warm
 

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