It is possible but unlikely. The one thing that could cause that is the wrong thermostat. You must have a 195 degree thermostat, that is critical to keep the engine up to the proper temp. But I don't think that would cool off the exhaust gas temps so it is unlikely.
Troubleshooting and diagnosing a hot rod can be fun up to a point. MP81 has much more patience than the rest of us. I thought I already replied to this thread but I guess it was this one. http://nastyz28.com/threads/81-5-0l-erratic-idle-no-start.329136/ Alls ya really need is a $50 Skip White distributor and unplug the carb and it will run surprisingly well. At least that was my experience.
The only reason I had that theory was seeing a few threads (on other platforms' forums) with CCC carbs and longtubes - the O2 doesn't necessarily stay warmed up, since it's so much further down, at least just at idle. The service manual does make mention of this as well. Thermostat is probably around there - I've never changed it - but the DD gauges have their own sender, so I get a digital reading of that to ensure we're where we need to be. Since I can't really go buy another dwell meter at the moment, is there a way to use a regular DMM (I do not think mine has frequency, nor does the old giant Micronta analog one I have in the basement) to look for a voltage on the dwell diagnostic to see if it is truly changing? I'm expecting not, since it'd need to be voltage/time, but maybe there's something I can probe on the MCS to watch for a change, just to make sure my whole issue isn't coming from a bad dwell meter.
Just a small update - since it was in the low 70s today, I decided to fire the car up to see. Me, being an idiot, didn't realize I had left the O2 unplugged since after the last startup, so that explains why it was a bit pissy, but also didn't allow me to test me theory. I plugged it back in, and then turned the car off. I moved the dwell meter so I can see it inside the car and started it again. Oddly enough, it showed me something other than "03" - it said "18". It said that for probably 20-30 seconds, then eventually switched to "03".
Yeah, it did. It gave me a check engine light (didn't check for a code), but I think it was looking for an O2 signal. The pooty running was partially due to the high idle cam not dropping like it should have on its own...but that's another issue (that usually stops after the first few starts of the season).
Bumping this back up as I've finally started the car for the first time in probably a couple months...and it tried to continue running after I turned the key off. Sigh...thought we were past that, but I guess not. Got me thinking - maybe there is something up with the MCS, and that's why it won't give me a dwell reading? But if so, wouldn't that throw a code? I've always read I should hear the MCS solenoid rapidly clicking with the key set to "Run", but I don't think I do. However, if I ground the "OBD" pins to read codes, I hear it cycling away. I still need to confirm about with the key in Run, but I honestly don't recall it doing that, given how loud they are with the engine off.
This is a tool that l had for working on a computer controlled carb on a 84 SS lt was a great help. You plug it in enter year and vin code. lt reads trouble codes mcs dwell, tps sensor position and others. Seem like a fair price https://www.ebay.com/itm/OTC-Monito...245646?hash=item446068a04e:g:kbkAAOSwYORfKDKm There are other on ebay cheaper maybe closer to you
You know, that's a good idea. I had seen those before, but hadn't acted on one. I really need to give this timing light/dwell meter back to my buddy anyway. This would be a lot easier to check while in the car. Update: bought it.
