I have finished my "Engine Bay Upgrade". It was a bigger project than I originally intended, but it's that "As long as I'm doing this... I might as well do that" syndrome.
I'll post up more pictures, but...
I had an interesting tuning activity today. I have a Demon 1900 on my Interceptor with an A/F Gauge and Vacuum gauge. I have been thinking it is running a little too rich, and have been monkeying with jets / metering rods and springs. You can change the metering rods and springs on the Demon without carb disassembly, but to change the jets, you have to take the lid off the body of the carb.
So I did that this afternoon, and stepped down a size on my primary and secondary jets.
It's a simple job. I put the carb back on and took the car out for a run.
About 100' from my house, I knew something was wrong, and about 1/8 mile, the car was pretty much dead, and wouldn't even idle.
Anyway - short story long,.... I rolled back down the hill and finally just barely got it back into my garage with starting fluid.
Earlier today (1 hour prior to the carb modifications) I had drove around for about 45 minutes, and the car ran great (just a bit rich), so I knew I have fuel, fuel pressure, good ignition, etc. It had to be something I did to my carb.
So I popped off the carb. First thing I noticed when I put it on the bench was the accelerator pump was pumping air. Psssst. Psssst. Not a drip of gas would squirt out.
I opened up the carb, and what do I find?
During reassembly - I had bumped one of the floats over, and it was jammed against a structure inside the carb lid. One of the bowls was completely dry (the one that feeds the accelerator pump) - the other one had gas to the normal level.
The float was jammed such that the inlet needle valve was shut. So one bowl couldn't refill.
So now I know what a V-8 runs like when only 1/2 the carburetor is putting in gas!
It was a quick fix. Just freed up the float, and it is now running great, and right in my "target zone" on the A/F gauge. The car is running great now, with A/F at "Ideal" for cruising, and slightly rich under heavier acceleration. Just what I had planned.
All-in-all, a good day.
For any of you running a Demon 1900 - and a "stock" 440.... I have:
* .074" Primary Jets
* .073" Secondary Jets
* 60/52 Metering Rods
* Silver Springs (8" Hg.)
Another Mystery Solved... "Intermittent Lean Spikes"
https://www.joc.org.uk/forum/viewtopic. ... 97#p215297
I learned that the way an Air / Fuel (A/F) Meter works - the system is ONLY looking at the oxygen levels for the determination of a Lean / Rich condition. So if you have intermittent ignition (which actually puts out pulses of exhaust that are too rich, as the fuel is not burned) - the sensor reports it as too lean (because there's a lot more uncombined O2 in the gas stream. This is because the sensor can't assess how much hydrocarbons are passing the sensor.
So my "intermittent lean spikes" were being caused by an intermittent ignition issue - since corrected.