350 carb on 305 block

[ricksl1]

82' mercruiser, well swapped out the origonal (305) carb it was acting up, running lean ..with a 350 carb remaned same yr ..ran GREAT in yard for 10 or so mins. After hookin up choke fiddeling around with other things ..came back started up and now it smoking ( rich) ...tried adjusting jets .. regapping plugs to 040 ( running pertronix flame thrower system) ..still smokin maybe not as bad ..sure plugs are a little fouled ...was gonna swaps the two jets around from carbs, but the new carb has bigger threads ,so no go there .. the motor is basically a mutt 350 4 bolt main ..the previous owner left the origonal 305 intake w/rochester carb ..still runnin rochester ...any idea on how to lean it out a little bit , outside fouling plugs and it runs good

 

[fabrimacator21]

Re: 350 carb on 305 block

Any idea on what the cfm's are for the 305 and 350 carbs? The 350 carb should be fine with the 305.

Might need some different jetting though.

 

[ricksl1]

Re: 350 carb on 305 block

really dont know the cfm's on either ..just thought being an older chevy engine i could simpely swap it out ...acctuator pump is the prob with older carb its sticking ,and only pumping on one side..Dang , just rebuilt it last yr ,worked fine then ..what exactly do the jets at the bottom if the carb adjust ?? air or gas ?...just tryin to get it to run a little leaner

 

[fabrimacator21]

Re: 350 carb on 305 block

Really don't know for sure what the jets do... I believe that it's just the size of the "sprayer". I don't know much about carb internals... more of a fuel injection guy.


I'm sure some else can shed some light.

 

[45Auto]

Re: 350 carb on 305 block

Not sure what you're referring to by "adjusting the jets". If you're referring to the 2 idle air adjustment screws in the front of the carb, all they do is adjust the amount of air at IDLE for a smooth idle. They have NO EFFECT on anything once the butterflies start to open.

What color is the smoke?

 

[gadget73]

Re: 350 carb on 305 block

The screws at the bottom are idle mix screws. The fuel/air is set by jets and metering rods. You have to remove the top of the carb to change those over. If you're going to all that bother, you'd be better off just rebuilding the original 305 carb since you'll need a gasket set either way.