And just 3* of idle timing is also retarded.
That slanty, to be any efficient at all will want plenty of timing for city driving, as well as cruising; plenty. Maybe as much as 40 or 50 degrees at 2000 rpm under light throttle conditions. That cannot happen without a well tuned Vcan, integrated with a fast and generous mechanical curve. You will also want to set the valves just right. And the power valve. Possibly even the float level. But if your cylinder pressure is in the basement, it's hard to pick up mileage under stop and go driving. Your combo can use a lot of tuning.
I can get great mileage out of my 2bbl. Not a lot better than the old single bbl that was on originally on it, but that's not why I put it on there..
So forget jets,for now, they have nothing to do with fuel mileage.
To get mileage in a given chassis, you need 3 things; 1) a decent cylinder pressure, and 2) the exact right ignition timing, and 3) the exact right A/F ratio, and 4) the exact right driving style.
-So, start with a very accurate valve adjustment, and a cylinder pressure test. I would also do a leakdown test if pressure is not pretty even. Normally, if pressure is down, there's not much that can be done, but in your case with the poor timings situation..........
-Next, Get the Vcan installed and working properly. The factory made all kinds of cans including a 20 * can. See if you can find one. If not,Find a can that brings in at least 14, as a bare minimum. I went to a local jobber, and he let me thumb through an old catalog. I wrote down several PNs and eventually got an 18*one, which I modded to 22*.
-Next, let's work on the dizzy! Put a T-lite on it and see what she makes, Just rev it up 'til she stops advancing, and grab the number. If you don't have a dial-back lite, you will have to mark your balancer at 10* intervals, all the way to 60*, or just get a stick-on timing tape.I would, of course, prove the TDC mark before beginning. Then If you don't get at least 36* of non-Vcanned advance, make it so. Then check the idle timing. You will want to see at least 8 to 12 degrees of true, proven, idle timing. Irregardless, grab the number.Now, Let's see what you got.
-Finally. And lastly. We will set the carb. But there's almost no advantage talking about that, much less doing something, until the timing is at least close.
-And then there's you. #4. If you can't keep your foot out of it, or circumstances don't allow it, or you live in hill country, or high country, don't expect much for fuel mileage. The slanty is severely W/P (weight to power)handicapped. It can return excellent results under steady-state cruise conditions, but it takes either; a lot of throttle, or a lot of runway, to get her up to speed; and that takes fuel.And if you need to do it 20 times a mile, well, you get the picture....
- So there you go. You got some homework to do. Come on back when the results are in, and the new parts are on.And BTW, if the plugs are old, well, that won't help.