Buick 350 2bbl W/ 4bbl Edelbrock AVS

Discussion in 'Small Block Tech' started by 1970BlackBird, Apr 12, 2020.

  1. 1970BlackBird

    1970BlackBird 1970 Buick Skylark Sedan, "Rosaline"

    So, in lieu of the availability of parts, as a temporary measure, I used a 2bbl to 4bbl manifold plenum on which I mounted a 4bbl AVS Edelbrock. With this measure, my 70 ran way better. Is there a reason for this and are there any repercussions as to the engine with this adapter/carb setup? Oddly enough, the flat spot of the off idle is null, the vacuum is perfect and unwavering and she is so smooth.
     
    Last edited: Apr 12, 2020
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The adapter would be a restriction which you would see on a dynamometer or at the track. You might not notice it on the street.
     
  3. 1970BlackBird

    1970BlackBird 1970 Buick Skylark Sedan, "Rosaline"

    Im curious as to why the Vac went from erratic to steady. Interesting, restriction in what way?
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Maybe you had a vacuum leak before, that got corrected with the adapter. Restriction to air flow. You have a 4bbl carburetor trying to breathe through a 2bbl intake adapter. It will be a restriction to maximum air flow that the 4bbl carburetor is normally capable of. I know you are probably happy your engine runs better, but it isn't optimal. Sorry to burst your bubble.:)

    Can you post a picture?

    Is this it?

    https://www.speedwaymotors.com/Mr-G...r-Kit-4-Bolt-2-Barrel-to-4-Barrel,287959.html
     
    Last edited: Apr 12, 2020
    70skylark350 likes this.
  5. 1970BlackBird

    1970BlackBird 1970 Buick Skylark Sedan, "Rosaline"

    Yes, this is the adapter
     
  6. alec296

    alec296 i need another buick

    The edelbrock runs rich down low and leans out cruise. It may seem to run fine. Get an air fuel meter.
     
  7. 1970BlackBird

    1970BlackBird 1970 Buick Skylark Sedan, "Rosaline"

    I had a bit of a wobble on my vac gauge with two two barrels I had tried. Oddly, the "adaptation" has perfect,unwavering vac. It sounds smooth. Though, im curious as a daily, could it hurt anything? My mileage dosen't seem to suffer
     
  8. 1987Regal

    1987Regal Well-Known Member

    It may not be proper or efficient but I can't imagine it would hurt it. Unless it is severely rich or lean .maybe your old two barrels bad throttle shaft bushing or a bad gasket. With Your 4 barrel (or 2 barrel) on you could always pull a few spark plugs out and see what color they. They should be tan/Brown is perfect white is lean, black is Rich. Sounds like you want just a runner, I don't mean anything by it other than you just want it in a rough ballpark to use it
     
    70skylark350 likes this.
  9. 1970BlackBird

    1970BlackBird 1970 Buick Skylark Sedan, "Rosaline"

    They are tan/brown. They used to be slightly black. I find this fascinating!
     
  10. 70skylark350

    70skylark350 Jesus loves you unconditionally

    I agree with the others, your performance issues were probably caused by the old two barrel, had you rebuilt or replaced with another two barrel you probably would have the same results you had with this new set up.
    aside from looking much cooler with the four barrel, you would only see the negative effects of a four barrel without the performance gains. the two barrel intake is choking off the air flow, more air equals more power. You would still be dumping more fuel in though so I would thing your air fuel ratio has got to be off?
    But hey if your happy with it, that's all that matters, go with it...... I have a four barrel intake in Pittsburgh.......
     
  11. DEADMANSCURVE

    DEADMANSCURVE my first word : truck

    i believe , from tech info somewhere , that the qjet 4bbl to square bore 4bbl adapters cost about 50-100 cfm . I would imagine the one you are using could be even a bigger difference .
    so , that's probably a 650CFM #1806 or #1805 AVS carb ? I've used a couple on my truck ( 360 mopar ) , ran good . probably fine for you if you are happy with it . with engine mod's you may run outa air a little bit top end .
    a TA intake would be nice with that . you'll need an adapter for the oem cast intake .
     
  12. 1970BlackBird

    1970BlackBird 1970 Buick Skylark Sedan, "Rosaline"

    I have used other kinds, but the vacuum had a bit of a jump, with the 4bbl on the adapter, it went away and ran quicker and smoother then I had ever seen. Its a curious thing. It wasn't overly rich, nor was there an issue with top acceleration. In fact, I got 10-15 mph more out of her.
     
  13. 1970BlackBird

    1970BlackBird 1970 Buick Skylark Sedan, "Rosaline"

    Its a 650 I believe, quite nice actually. Starts up and is crisp from the get go. No gas saturation in the oil
     
  14. nekkidhillbilly

    nekkidhillbilly jeffreyrigged youtube channel owner

    mine is currently the same setup. it dont run bad at all. i will be pulling it off later to drop on a 4 bb intake though and a efi unit.
     

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