Just asking here but what year is your 261 and what is the delco number for your distributor. Take the cap off, it’s stamped on the distributor plate. If it ends in 2403, you have the 56-63 distributor. These distributors are generally 12-14 degrees of mechanical advance which is 24-28 degrees at the motor. It’s always a question as to whether any particular distributor is actually getting to full advance.
Several months ago I had a nos 2403 distributor on my sun machine. Could not get anywhere near what it should have been. Took it apart and between a little surface rust and dried up hard factory grease, the advance weights were not extending and retracting properly. A little cleaning, polishing of the weights and fresh grease and it was back on track.
What I would do is figure out what year motor you have and see what the timing for that year is supposed to be. Some are Tdc others are 5 degrees before Tdc (advance). Set the octane selector plate at zero, set the distributor to Tdc or 5 before using the bb on the flywheel and the pointer on the bellhousing to set that up. Once it’s running, you can add a little advance by turning the distributor counter clockwise. If you have a dial back timing light, this process is a little easier. You add a little advance, adjust the idle speed. Take it for a drive. Add a little more, take it for a drive. If you hear pinging, take some timing out of it. It would not surprise me to see that motor take 8-10 degrees advance with todays fuel.
One last thing, you do not adjust the timing by loosening the octane selector bolt. Set that on zero and leave it alone. You set the timing by loosening the screw on the vacuum advance/distributor clamp.
Last edited by Dragsix; 09/11/2022 2:17 PM.
