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I picked up this carb https://www.ebay.ca/itm/144495270143 off Ebay after struggling with my Carter YFA 7051SA for months of fiddling around. But the design of it is drastically different visually and I'm curious if anyone has any ideas on how to best tune one of these? The idle screw is on the opposite and there are a couple vacuum ports I can't figure out what they do so I've capped them for the moment. I expect I'll figure it out with time but thought if someone already knows I can save myself and future people some time investigating this. Both of those ports go in but I'm not sure what they connect to.
The brass port is the bowl vent, nothing goes to it, it stays open. That square chamber on the front of the carb in the picture is the fuel bowl, it works like the tank on a toilet bowl. The fuel bowl has to breath as fuel is coming and going out of it, that is what the brass port is.
The large port pointing down is also a bowl vent. When the truck is stopped, the fuel in the bowl still breathes, and instead of filling up the aircleaner by using the brass vent, they hook a hose to this vent on the front and run it down to the charcoal canister, where the fumes are stored. Then there is another line from the canister back up to the engine where the engine sucks on the canister when it runs and pulls the stored fumes out of the charcoal and cleans it out, getting it ready to store more fumes later. It's more complicated than this, but that is what some of those vacuum lines running all over the place were for. If it runs ok plugged, leave it. If it's a little hard to start in hot weather, you can unplug this line and leave it open and see if it helps it starting in hot weather.
The port on the left side of the picture is the fresh air intake for the choke hot air system.
That carb looks like it is a feed back carb.
That plate on the right side held on with 2 screws is where the solenoids bolt up that the computer controls.
Dave ----
Interesting. When the engine cools off I might open that up and check. I may have been over thinking this and I might actually have it running. If I can trust my little aftermarket tach I have it idling nicely at 800 rpm.
Make sure the timing is set while the motor warms up, vacuum to distributor removed & plugged.
Once set hook up vacuum gauge to intake set idle by the tach, 800 is good.
Then adjust the idle mixture screw to get the highest vacuum reading.
You my need to readjust the idle speed when adjusting the mixture.
Dave ----
Yeah I realized I was doing it wrong and went back, I have it sitting at 18" of vacuum now consistently at around 850RPM. I backed both screws right out and then did them both a little bit at a time watching the vacuum.
Ok so the outer flair by the fuel intake and the brass one in the main body are definitely related, when I plugged both with my fingers the engine stalled immediately. I "believe" that outer port should run to the weird orange filter that is on the side of my air clearner? Or if I'm reading Franklin right I should just put some kind of filter to stop crud from getting in there and leave it open?
Ok so the outer flair by the fuel intake and the brass one in the main body are definitely related, when I plugged both with my fingers the engine stalled immediately. I "believe" that outer port should run to the weird orange filter that is on the side of my air clearner? Or if I'm reading Franklin right I should just put some kind of filter to stop crud from getting in there and leave it open?
Ok so the outer flair by the fuel intake and the brass one in the main body are definitely related, when I plugged both with my fingers the engine stalled immediately. I "believe" that outer port should run to the weird orange filter that is on the side of my air clearner? Or if I'm reading Franklin right I should just put some kind of filter to stop crud from getting in there and leave it open?
They are both bowl vents. Just leave them both open. The only problem you may have is if you hit the brakes hard enough, you might get a little fuel to spill out of the port up front. If you do you can put a rubber line on it.
Question on the same topic. I had my stock carb apart for a rebuild last year and have been chasing some flooding symptoms and vacuum leak ever since. I pulled it back apart after talking with Mike over at mikescarburetor. Adjusted the float and made sure the needle and seat were good.
As I was putting back in the truck I noticed that the silver vacuum port on the right of op’s photo is just an open hole. There’s no barb or plug. Guessing what was there came out during my rebuild without me noticing. So my question:
my canister is gone and the egr was blocked off by my old man not long after he bought it new. Given that, can I just plug this hole? Or is there a source of vacuum on the carb I should run this to?
Dent you can plug it if you want, no need for it to go to vacuum.
The reason that went to the canister was to trap and hold fumes till the motor was running and then would be pulled in and burned.
IIRC my Ebay carb dose not have that nipple so I removed the Tee and only have the canisters (dual tanks have 2) catching the vapor from the tanks to be burned.
You only need a few vacuum hoses hooked up.
Power brakes if you have them to manifold vacuum.
PCV to manifold vacuum.
HVAC controls if you have factory AC to manifold vacuum.
And ported vacuum on carb to dist.
Dave ----
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