65 289 stumbles at lower rpm during accelleration.
I rebuilt the Autolite 2V carburetor, put in new points, condenser, rotor, cap, and vacuum advance (generic for an M2100). Vacuum at idle is 21 in/m. The vacuum is hooked up to the ported inlet on the carb, and has no vacuum at idle. I set the timing at 6 degrees BTD with the vacuum advance disconnected and plugged, set the Dwell at 28(.0017"), and idle at 550 RPM, per manufacturer spec. Also adjusted the idle jets. Now, when I run the throttle up by hand, it stumbles around 1500 RPM. Tried adjusting it out by manually changing the timing, but nothing would change. The only thing that gets rid of the stumble is to disconnect and plug the vacuum advance. It runs great this way, but I know this is not good for daily driving. The new vacuum advance does work, as I tested it before installation. Is there a specific type, or adjustment for travel at vacuum level that needs to be made to set the vacuum advance? There are no obvious vacuum leaks, and the engine idles and revs smoothly without the vacuum advance connected and it's port plugged. Trans is manual.
There is a adjuster screw inside the vacuum advance port, it is allen configuration, but you need to check out the breaker plate in your distributor it sounds like it is worn out. When that happens the dwell and point setting will change as rpm's increase and the vacuum advance starts to pull on the breaker plate to advance the spark, it will change to the point that the engine will start to misfire cylinders due to the points not opening as the distributor cam just slips past the point block not opening the points. Blue point used to make a breaker plate that had a solid shaft with a brass bushing where the plastic one normally would be, they were great for higher RPM's. I hope I have sent you in right direction.
When you rebuilt the carburetor the accelerator pump is adjustable by moving the small linkage to different holes. The 1965 Manual I have, has the rod in the in-board hole of the pump arm and 3rd or 4th hole from bottom of shaft on throttle lever.
Not enough volume of fuel discharged from the accelerator pump will cause a off idle stumble, Too much black smoke out the tailpipe when accelerating.
I replaced the breaker plate, as well as a new vacuum advance when I discovered the other new one was defective. I would not move, even using manual pressure on the breaker plate linkage. You were right about the breaker plate. It was a cheap aftermarket replacement, and was starting to come apart where the spring tensioner held the top plate. The retainer clip was coming off the top of the deteriorated plastic/nylon post. This resolved most of the problem. I still get a small amount of hesitation on acceleration, but not much, and not when accelerating easy. uch thank's, John
Troy, The accelerator pump linkage is set to the 3rd hole up from the bottom of the linkage, and the inner hole on the pump arm. It is a good snug fit, and squirts immediately when the throttle is depressed. John
I would change the link arm to the outside hole on the arm, and back off the spring tension about 3 turns inside the vacuum advance unit and give that a try. You might have to do a little "drive and adjust" to get it just right. Are you running ethanol free fuel? If not try putting in some marine fuel stabilizer.
Changed the linkage, but it runs much better with the spring tsnnsion set as tight as possible. Have not tried the fuel stabilizer as of yet.