Street Demon 750 carb review

Discussion in 'High Performance Modifications' started by biker, Jun 14, 2018.

  1. biker

    biker Veteran Member

    Just installed a 750 street demon with the composite fuel bowl. Most reviews I had read and watched were favorable, so I thought I would give it a shot. The poor reviews seemed to be the result of user tuning, except for one I saw where the carb was shipped and installed with a gasket improperly installed, causing a leak.

    Stock fuel line will not fit, since the fuel inlet on the carb is at the back passenger side. Comes with adapters to fit different fuel lines, including quadrajet style. There is no filter in the carb, so I installed a filter in the new line that I had made at a hydraulic shop.

    There is no 3/8 vacuum fitting on the front of the carb. There is ported vacuum, which I ran the vacuum advance to. Relocated PCV to back passenger side for easier access to manifold vacuum port at rear of carb. Brake booster port back there as well.

    Throttle linkage adapter included, worked perfectly with my 81, stock clip and throttle return springs worked perfectly.

    Carb bolted on to my Performer RPM Qjet manifold perfectly. Gaskets and adapter plate included.

    I have a very low dropped air cleaner base that allows me to use a normal 14x3 Wix race filter. The choke housing on the Street Demon interfered with the base, but just barely. I cut into the base, and had it properly tig welded to seal it up. Fits great. Hood closes, no problem.

    Initial start up was great. Auto choke works perfectly, easily adjustable if needed. I didn't need to. As soon as bowl was full, engine fired and went to fast idle. Once up to temp, easily kicked down off fast idle, watched electric choke open up nicely.

    Very minor adjustments to idle mixture and idle speed, settled at about 950 rpm for my engine.

    I was worried that there might be some lean stumbles or other quirks, but it works flawlessly. Great throttle response, wide-open throttle and hot/cold starts. No drama whatsoever.

    My modified quadrajet ran great at WOT, but was always leanish at idle and low speed driveability was finicky. The Street Demon runs fantastic and was easy to install. I wouldn't hesitate to put one on anything.

    Brent.
     
  2. Scaleytail

    Scaleytail Member

    33
    4
    Jun 12, 2016
    North Aurora, il
    Basically felt the same about 650 Speed Demon with the black poly bowl. Throttle response was wicked quick. A user friendly carb over all. Thinking in the future to change to the 750 Demon on my new engine over the Holley 3301 I have now.
     
  3. John Wright

    John Wright Veteran Member Lifetime Gold Member

    14,148
    81
    Aug 9, 2002
    Rustburg, Va
    Hi Brent,
    I have a friend who just put one of those on his 73 Corvette. He basically said the same thing that you did. Crisp revs and no stumbles anywhere in the rpm or load ranges. I noticed that his choke isn't set right and wasn't opened all the way up(motor was hot from driving over to my house), but I'm sure he can adjust that pretty easily.
     
  4. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    9,372
    240
    Nov 4, 2004
    Ringgold, GA
    Brent, what's your engine combination?
     
  5. biker

    biker Veteran Member

    Yes. Spring tension is adjustable at the housing just like a quadrajet. Does he have power to the choke? If the wire isn't hooked up or powered, it will at least slow or maybe prevent opening.
     
  6. biker

    biker Veteran Member

    Small block 383, 10.1:1 with 540 lift hydraulic roller cam and Performance Distributors HEI. ATK aluminum heads and a 4 speed super T10. I was worried that the cam duration might make it finicky, but I have 7" of vacuum at idle which seems to be enough to hold the primary needles closed. Very smooth transitions with primaries and secondaries. Very crisp, and settles down nicely at idle.

    Just thought I would post a real world review after seeing some negative stuff out there.
     
  7. Zstar

    Zstar Veteran Member

    1,208
    249
    Mar 23, 2014
    Ocala, Florida
    I have a 650 Street Demon and completely agree with all of the above.
    Very easy to tune.
     
  8. John Wright

    John Wright Veteran Member Lifetime Gold Member

    14,148
    81
    Aug 9, 2002
    Rustburg, Va
    His is the 650 Street Demon. I didn't pay any attention to whether he had power to it or not...that may have very well been his problem. I told him that to adjust it was a matter of loosening the screws slightly at the spring and rotating it until the choke opened all the up when warm and retighten the screws around the spring.
     
  9. PalmbchZ28

    PalmbchZ28 Veteran Member Gold Member

    678
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    Jan 29, 2017
    West Palm Beach Fl
    Nice review Brent thanks for posting.
     
  10. 1980RS

    1980RS Veteran Member

    1,745
    44
    Jun 17, 2006
    MN
    Glad to hear your Demon carb worked out for you. Most of the early troubles were from poor machining but after that was taken care of most of the Demon's turned out to be pretty good. I have used several from 650 to 850 with A/D boosters all worked well but the 750, I did not have enough time to tune it that day but after a little fiddling around I am sure it would work fine. I do know the mighty Demon's work really well in race applications.
     

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