need to know what the proper jet size and power valve is ofor a chevy 305 ho motor? what is on it now its burning rich? help guys please. thanks,matt

 

MorTec, Inc. Home Page will have the stock jetting and PV for your carb.

 

Its really a trial and error deal to get it just right, but I would start around 67 primary jets, 75 secondary jets, and a 6.5 power valve. Make adjustments and changes as needed from there.

 

ok guys . it has 66 jets in the front and 75 in the rear 6.5 poawer valves. the set screws are at about 1.5 turns out. it still has black smoke coming out the tailpipes. not allot but you can smell the gas coming out the tailpipes. the plugs and all that are new.the plugs are split fires. what else can it be? maybe too big of carb? thanks guys,matt

 

Its not too big, 600 is just fine. I would change the plugs for regular AC Delco or Champion copper plugs though. Those gimick plugs like the multi-electrode plugs never work nearly as well as a regular plug.

Now, is this a vacuum secondary carb, or a mechanical secondary carb (double pumper)? What accelerator pump cam(s) do you have on the carb? Just need to know the color of the cam, as they are color coded. I would suggest using the white cam on the primary side.

Also, does your carb have just one power valve on the primary side, or one on the primary side and one on the secondary side as well? If you have two power valves, I would suggest removing the secondary power valve and replacing it with a plug.

When does it smoke black? Cold start? Warm idle? Acceleration?

 

Might want to look into this first. What do the spark plugs look like? Check your fuel level, bad float, blown power valve, fuel pressure to high, bad needle-seat... could be any one of these. Easy way to check PV turn the air fuel screws all of the way in; if the engine starts and idles without stalling, most likely a leaking or bad power valve.