I have been working on smoothing out the performance of my 250 engine. So far here is what I have done: Had the original carb rebuilt (done my an older gentleman who owned a carb shop for 25 years, really knew his stuff). Changed over to the Pertronix electronic ignition with a new matching coil. New Autolite platinum plugs, gapped at 0.040" (slightly over spec for the electronic ignition). Timing set to 6 btdc. New plug wires cap and rotor last summer. New fuel filter. Checked compression, looks good, all cylinders between 165-179 psi. Did the suction test on the vacuum advance and it pulls and holds fine. It basically runs great except the cold idle is rough. I am wondering if this could be that cold temperature activation system? Its a 1974 and still has all that stuff in place. Should I just try removing it all? I have read in other threads that with the cleaner unleaded fuels today this system really is not doing anything from an emissions standpoint. One other thing I may look into is the distributor end play, it seems a little out of the 0.033 spec but I need to borrow a dial indicator to check that out. Thanks for any advice.
If choke plate isn't open at least slightly, engine will run rough when on fast idle. If fast idle is too slow it will idle rough.
Your were right on target. I didn't get around to it until this cold weather kicked in but the auto choke just needed a slight adjustment. It was set on the mark in the specs. but just needed to go one more notch. Also I notice that the PCV valve was chattering alot. I pulled the hose and put my finger over the end of the valve and it ran even more smoothly. I am wondering if that PCV valve is not the correct one and allowing too much air flow and dropping my vacuum down.
That's possible, many companies selling PCV valves think one size fits all. Also some vacuum sources can cause a chattering PCV valve. That's reason on V8, vacuum is usually sourced from spacer under carb, can draw from both sides of intake. Making sure the best idle possible(most vacuum) often improves PCV action. I've used 4 cyl valves on V8 to get a smoother idle. One for a 2.3L 4cyl may be worth a try. The ones used on '80s 2.3 fit into a hose but are same size as ones fitted into oil fill cap.
