The ones it came with from the manufacturer. If only it were that simple, I would be out of a job. Guys like that make me money so I guess I won't complain. Rule #1 of carb. tuning eliminate all variable that are not the carburetor. Your main target is the distributor, is it a stock GM HEI, if so you will need to pay attention to the mech. and vac. advances. The mech. is usually stuck, rusty or worn out. In any case it will need cleaned and greased, also the springs are probably too stiff for performance use, install lighter ones. You will need to limit the vac. to between 8* and 12* degrees, I like the vac. can from 454 motor homes it's a 10* can and works well on street cars. If set up properly you have a advance curve of 12* to 18* initial timing, with the vac. advance disconected and the motor reved up to 3,000 RPM or whenever it stops advancing, you should see between 32* and 36*. Now plug your vac. advance in and repeat, now you should see between 40* and 48*. Make sure to plug your vac. advance into the small passenger side vac. port at the front of the carb. as it is ported vac. you don't have enough valve overlap to need the manifold source on the drivers side. After you get your timing somehwere in the ballpark hook up a vac. gauge to the driver side vac. port and take a reading. If the motor is warmed up and off the choke you should see about 15" of vac. with that cam. The more inital timing you have the more vac. you will see but don't just crank a bunch of initial into it to get a high vac. reading you will be going the wrong way. Set your curb idle speed to between 750 and 850 RPM, make sure it's not dripping fuel out of the booster venturiis, recheck your initial timing and make sure you have no vac. signal on the front passenger side vac. port. Your forgot to mention if you have a 1405 or 1406, the 1405 manual choke carb is jetted .007 richer on the primary side, way too much jet area for a mild 305. If you have a 1406 just swap the main jets front to rear and install a different set of power piston springs, factory jetting is .098 front and .095 rear. Leave the stock metering rods alone for now, they should be okay, 75/47 for the 1406. You can use the plain silver or pink ones, the silvers will give you more power the pinks a little better economy. They are usually a little rich on the primaries even with the leaner factory jetting and a little lean on the secondaries especially with headers, cam and manifold. Just make sure to change out the step up springs, they sell for like $8 at the auto parts store. Also make sure to adjust your trans. kickdown properly, and check for wide open throttle, make sure your secondaries are open at WOT, with the engine off of course. Good luck let me know if you get it figured out.
Andy Stafford
Performance Tuning
509-521-2910
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