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?