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2 barrel or 4 barrel

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by paddyjim, Jun 9, 2002.

  1. paddyjim

    paddyjim Registered Member

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    My son and I are replacing the old worn out 305 in our Blazer with a reconditioned 350 Marshall engine. We have pretty much ageed on everything as far as bolt on products are concerned (headers, guages shocks etc.) But we have run into a little snag as far as intake and carbs are concerned. We both belive that an Edelbrock performer intake with an Edelbrock 650cfm sitting on the top would be the right thing to do. But my son is a little short on cash. He has been talking about putting on a factory cast iron (pre emission) 2 barrel intake, with a stock gm 2 barrel. I am not sure whether that is a good idea or not. Is it possible to "under carburate" a 350? He is more concerned about it being economical that than a high performer. Will probably be the daily driver grocery getter. I am looking for some opinions on the subject. 2 barrel or 4 barrel? Any information would be greatly appreciated.
     
  2. big d

    big d 1/2 ton status

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    2 barrel would definetly be more economical. truth be know, 4 barrel arent really used (secondaries) unless you really kick it in the ass. i imagine a two barrel would probabley be easier to rebuild and cheaper also. i dont really know about the edelbrock performer manifold and two barrel carb bolting up together (designed for performance along with a 4 barel carb) but i imagine it could be done- alot of adapters out there available at any auto parts store. my two cents.
     
  3. Thunder

    Thunder 3/4 ton status

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    Well if he is looking for economy, go with the 2 barrel.
    I had a 71 Olds cutlass with a 350 and a 2 barrel carb It got around 22 MPG It was no race car but it did have plenty of power. . I'v also had a few trucks with v8s and 2 barrel carbs and they ran just fine.
    The old Rochester 2GC carbs that were used on older GM V8s were a good carb. They also work well off road.
     
  4. XHitman396

    XHitman396 1/2 ton status

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    the rear 2 barrels in the 4's aren't even used except for open throttle high rpm's (as far as i know) so go with the 2 barrel
     
  5. 350S10NJ

    350S10NJ Registered Member

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    I know you said money was an issue right now, but a 4 barrel Q-jet will be better on gas than any 2 barrel as long as you keep your foot out of it. Here is why, the primaries on the Q-jet are smaller than 2 barrel and will use less fuel.
    I have tested this and found it to be true in both my truck and boat
     
  6. HarryH3

    HarryH3 1 ton status Author

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    I used to have a Dodge 4WD 1-ton van with the factory 360 and 2 barrel carb. It got 6 mpg. /forums/images/icons/shocked.gif I installed an Edelbrock Performer intake and a Holley 600 CFM 4 barrel carb and not only did the engine run better, but mileage improved to 11.5 mpg. /forums/images/icons/cool.gif

    With the 2-barrel, just going up a long, slight grade on the highway would have the throttle blades open so far that manifold vacuum was zero. It was so bad that if the a/c was running, it would start blowing through the floor vents because there was no vacuum left to keep the air flow control flaps in the correct position. Once I would top the grade and let off the loud pedal, the vacuum would go back up and the air would start coming out of the dash vents again. /forums/images/icons/cool.gif Once I installed the 4-barrel, all of that nonsense stopped. /forums/images/icons/laugh.gif
     
  7. muddin4fun

    muddin4fun 3/4 ton status

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    IMO, a blazer is too heavy to be running a 2 barrel. As long as you don't floor it it will only run on 2...but if you need the power it's there.
    I'd go with the 4
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    This is correct for sure with a Q-jet, but not so on square bore carbs. I'm only pointing this out because an Edelbrock was mentioned.

    A 750CFM Q-jet (pretty standard in the late 70's on Chevy's) has 250CFM primaries, which results in good throttle response and economy when tuned. A squarebore 600CFM carb(like an Edelbrock) has to flow 150CFM per barrel obviously. So 300CFM on the primary side.

    I'd say stick with a Q-jet. I can't believe people are still SELLING used 4 barrel cast iron intakes...more often than not, they simply get tossed when someone changes to aluminum. In other words, you should be able to get a cast iron intake for nothing in my opinion, and at worst, $20. Heck, if you were willing to pay shipping, I bet someone would send you one for shipping and handling alone if you advertised in the parts for sale/wanted section. I know I would if I had one laying around!
     
  9. Blue85

    Blue85 Troll Premium Member

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    I also suggest a Q-jet. Tiny primaries, huge secondaries, central fuel bowl, easy to find and cheap in junkyards. The only thing better is fuel injection. And when more money comes later, swap the intake manifold and maybe have a shop tune the Q-jet for exactly what you want.
     

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