Hey guys, I hate posting on places like this asking for help, but I’m grasping at straws here.
79 SA, been running with a DCOE45 for over a year now, with a wideband. Car was running pretty great all season, only complaint was the AFR was pretty rich on the highway, high 11s. I switched the thermostat from a 85C to a 75C thermostat because the upcoming track days were slated for days where the ambient was going to be very hot. Drained the coolant, swapped the thermostats, let the car idle in the driveway for 30-40 minutes bleeding out air of the coolant. Parked the car in the garage, and didn’t think any thing of it.
The next day I fire the car up to go for a drive, and it’s pig rich everywhere. Adjusted the idle screws to get a decent idle AFR (13s). Full throttle, it’s in the 9s I notice.
I’ve checked coils, MSD blaster high vibration coils, they ohmed out as per factory. Checked them with a in-line spark tester, noted that the leading coil would barely light up. Replaced both coils as a precaution. Plugs are new. Spark plug wires are new, and ohm out properly, also tested with a pair of old plug wires that were confirmed good. No change. Distributor cap is new, but confirmed no change with a known good one. Ignitor ohm out as per the factory (using a 82 electronic ignition dizzy). The carb is only one year old, but I striped it down, cleaned all passages out with air and carb cleaner. All new gaskets.
I performed a compression test, with a standard tester with the schrader pulled, 95psi on each rotor face. I’ve done the test for vacuum leaks, using propane while the engine is running, not leaks found.
I’ve tried playing around with jetting to see if anything changes, but nothing found.

DCOE settings before anything went wrong:
36mm chokes
150 mains
175 air correctors
f16 tubes
65 acc Jets


55f8 idle Jets (I’ve tried 65f9 idle jets, but that’s far too rich for it, you can hear it missing when it’s Rev’d to 4K rpm).
3psi fuel pressure.
I’m at a loss of what could change so drastically over night. Any insight would be appreciated, as I’m really at a loss.

 

Can you check if the float isn't stuck?

Only thing I can think of at the moment.

 

Thanks for the reply!
ive disassembled the carb and set the float level more times than I can count. I’ve even tried a spare float I have. 14mm float height (I’ve tried 12.5mm as per a different manual), with 2mm of droop.

 

coolant temp will affect AFR's. i wouldn't worry too much about it, but you might try 50 idle jets, and maybe smaller mains

 

As stated in the original post, the AFRs are in the 9s, it’s so rich that it breaks up. A particular note was that the AFRs were good before hand. I’ve recently changed the thermostat back to its original temp, and conditions have not improved