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305 to 350 swap on 85 GMC Jimmy, Carb help

bkstradlingbkstradling Member Posts: 1
edited March 2014 in GMC
So I'm swapping out my engine in my Jimmy and trying to figure out what to do with my carburetor. What I'm mainly told is that I need to get it modified or machined so that it isn't running too lean, the 350 being a larger engine and all....
Anyways, it would be nice to just get a new one that fits on there right, but the problem is that my carburetor is a computer controlled carburetor which seems to be kind of rare. I do need to pass emissions... and am wanting a carb that will give me some good performance off road.
Any suggestions?


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    tommy42tommy42 Member Posts: 70
    I swapped 305 to crate 350 in a 82 blazer.Every thing bolted on the 350 from the305.The blaser run great.
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    1986blazer1986blazer Member Posts: 6
    i do not know what kind of carb you got, but if you plan on replacing the carb, you will need the rochester quadrajet wich will work fine and you sould be able to order it from autozone.
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    1986blazer1986blazer Member Posts: 6
    i have an 1986 k5 blazer 4x4 with 3.73 gears, and with the recent raping that we are taking from big oil, i need to do some modifications to get better fuel economy. please help i am willing to try anything the more ideas the better, if someone suggests changing gears i would like to know how high i can go without doing any damage to the drivetrain
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    okko1okko1 Member Posts: 327
    do you have an auto or manual trans. 373 with 4 speed auto is not bad. the problem is you have to make front to rear gear changes. the cost minus the assumed savings may justify leaving it alone. :shades:
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    paisanpaisan Member Posts: 21,181
    Do you need a truck? I'd look for a more economical car in terms of gas if you don't absolutely need the truck.

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    ahinsonahinson Member Posts: 17
    what is the timing for 86 chevrolet 350,ie 2,4,6,8,DEGREES .the sticker is gone on the radiator support that usually tells you. thanks. ;):cry:
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    burdawgburdawg Member Posts: 1,524
    Changing the gear ratios from 3.73 won't be much help. That is already a very good compromise between economy and effeciency. 3.42 was higher ratio for those years, not sure if it was available on a Blazer though. I had an 85 Suburban with 3.42, it was OK on fuel mileage (well, for a carbureted Suburban anyway), but absolutely was terrible at towing anything other than a light load.
    The best modification you can do is to your driving habits. Slow down, try to stay in higher gears, leave it parked more often.
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