Over the past couple years, my truck (51 3100 with 1962 235) has run beautifully. Easy starting. Plenty of power and responsive acceleration.
A few weeks back, about the time I was doing a very extensive cooling flush, I noticed it was down on power not running as smoothly as normal, etc. It sure "seemed" like ignition timing, but I resisted the urge to go there right away. Pulled one plug wire at a time to make sure all cylinders responded the same. They did. Stuck the dwell meter on it to make sure the points gap hadn't closed up. That was good as well. Didn't have time to go over everything with a fine tooth comb, so I went ahead and advanced the timing by ear. Idle picked up. Throttle response was snappy. Locked the dizzy collar back tight. A couple of road drives and it felt like my truck again. No issues. Thought it was weird for the timing to have slipped, but figured it was possible.
Fast forward about 2-3 weeks. Been out of town and truck hasn't been driven. Had an appointment for a HS girl to use my truck as a senior pic prop....so went out to start the truck. Other than being a little slower than normal to fire (fuel always evaporates from bowl in that time span)....the drive TO the photo shoot as mostly OK. I'm not sure it was running 100% perfect, but certainly decent-ish. Very hot day here in SE MO. Miserable.
On the ride home (5-10 miles), which included a trip to the gas station, truck was definitely acting up again. Sluggish. Low power climbing hills. Almost exactly how it acted BEFORE I bumped the timing. It was dark by the time I got home, so didn't have time for further diagnoses. One other item of note, it's fairly normal for temp to creep up after shut off (truck still ran at 180 while moving), but the coolant was actually BOILING in the overflow. Checked the inside gauge and it had indeed climbed to 210. Getting hotter after shutdown is pretty normal. I don't recall it ever boiling like that.
Some thoughts on next steps:
1) I have most everything I would need to do a complete ignition tune-up: NOS points. One of Jon's fancy condensers. New plugs. It's probably time for both of those things, anyway. But before I just start throwing parts at it...thought it might we worth sharing this story and seeing where else I might look. Ignition system is just my first hunch.
2) Difference between the trip away and the trip back home last night. All I can figure is that the engine would have been warmer coming home. Could the coil or ignition switch be getting heat sensitive?
3) The (apparent) slippage of timing a few weeks ago, and the way it responded to advancing, has me a little baffled. Especially now that it is acting the same way again.
