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I am reposting this as the other thread I had went dry.
My remanufactured motorcraft 2150 carburetor is pulling about 5in from the ported side at idle, which is around 750rpm. I know that this is happening because the throttle plates are too far open, and exposing the ported side. However, I have tuned the carb multiple times, reset the timing, and nothing gets ported down to 0 at normal idle, let alone up until 1000rpm.
My engine is a stock 1977 302, with the timing set to 9*.
Vaccum on that port is a matter of throttle plate position. most likely if you increased your initial timing you could close the plates enough to clean it up. of course you'd have to check your total timing to be sure you didn't create other problems.
As long as it runs good so what if you have a little vacuum on it anyway.
The carb was remanned in 2018, from Uremco. The PO got it. The initial was at 6, and the ported vacuum made it 8. I was allready getting pinging, and this is how I discovered the ported vacuum.
I forgot to say, but I currently have it tuned to 550rpm, as that is where the ported vacuum just stopped. The idle is somewhat choppy at this rpm.
The ported vacuum at idle will have no effect on your vacuum at operation speed so don't worry about it. if you need to limit your vacuum advance to prevent pinging that's another matter.
If you're pinging under heavy load or WOT that's a mechanical advance issue. if it's pinging at cruise speed you very well may have too much vac advance. what is your total with the mechanical and the vac advance all in at 2500 ?
Im not worried about the vacuum being poor, as manifold is a steady 19in. However pinging is what I am concerned with. Cruise is fine unless im going up a hill in 3rd, so its under load is what the problem is.
That is with vacuum advance hooked up. 22* doesnt sound right, but these engines are supposed to only go to 36*, according to all the people online. As long as the front passenger cylinder near the alternator is cylinder 1, then im on it
They're supposed to go to 36 on mechanical, then to 50-60 with the vacuum advance added. so your vacuum advance must be doing nothing and your mechanical is way low.
if your readings are correct it should be really gutless, run high EGT's and get crappy fuel economy. but you wouldn't be getting detonation with severely retarded timing so something isn't right.
what ignition are you running ? what do your plugs look like ?
At least at idle, vacuum advance is doing something.
This could be a completely bs theory as i dont know a whole lot, but could the pinging im having be caused by vacuum advance coming in at the wrong time? If I understand correctly, at cruise there should be no vac advance. Since there is vac advance already at idle, this could be messing it up. But again I have no idea
The ignition is a Accel 8140. The plugs look normal.
At cruise speed is where all your vacuum advance should be in. when the engine has a light load at higher rpm it can benefit from more advance . when you open the throttle the vacuum drops and with it the advance preventing detonation. vacuum advance can cause pinging if it's excessive but if your total with vac advance is 22 then your timing is retarded and certainly not excessive.
I'm thinking either your readings are incorrect or your ECM is messed up. it doesn't look like fuel starvation and what you're describing isn't adding up.
What does the ECM do? I saw it does something with starting. The one in my truck looks like it has been replaced somewhat recently, shiny and clean wires.
Engine control module. I'm not familiar with your set up so I'm not sure how it works. generally the symptoms you have wouldn't be contributed to the ECM but what you have going doesn't make sense.
Just to cut to the chase I'd set your total mechanical to a safe 30 then hook up the vac advance and see what it all comes to. if it starts and runs good take it out and see if it pings. assuming you're confident with your readings if that doesn't work I'd start trying something new. like stock ignition .
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