Double pumper tuning tricks?

Discussion in 'Tips 'n' Tricks Topic' started by Crusty75, Sep 29, 2016.

  1. Crusty75

    Crusty75 New Member

    Jun 16, 2016
    First off, sorry if this is posted in the wrong section, I had trouble deciding whether to post here or in the engines section. Chew me out if need be!

    A Holley 750 double pumper has fallen into my lap, and is going atop a mild 350 in my 1975 Camaro, replacing a tired and badly tuned Quadrajet that I'm just sick of messing with. It's got a th350 with an 1800 stall and a 3.08, not optimal, but I'll shift in manually most of the time most likely anyways. It'll get a 2400 stall in the future.

    This is obviously way too much carb for this engine, but I think it'd be silly of me to not at least stick it on and try it out and see what I can make it do, especially since a complete revamp of the engine is in the works anyways. Worst case I just pull it off and trade it for a 650 VS carb.

    The carb and a Weiand intake that comes with it was out of a buddy's special ordered 1972 Chevelle SS 350 that as far as I know wasn't much hotter than my 350.

    I don't have the carb yet, my buddy still has to find it and dig it out, but I'm assuming that it'll need a rebuild.

    What tips and tricks do y'all have to make this junk run? Any particular rebuild kits that are better than others? I know fuel mileage of any sort is unrealistic, but I'd like to at least maintain double digits, but drivability is top priority. If I really needed good MPG numbers, I shouldn't be driving a Camaro!

  2. giggity

    giggity Veteran Member

    Mar 18, 2013
    Pearland, texas
    you will suffer throttle response on the engine most likely. Use a Holley rebuild kit, there are tons of resources available like you tube videos on DYIs.

    Gas mileage? LOL

    Keep your foot off the pedal and you will get mileage.
    BackyardCustoms likes this.
  3. MagicRatt

    MagicRatt Veteran Member

    Aug 24, 2004
    Southampton, Pa.
    Get a Holley book...great bathroom reading material!! I bought my holley book 30 years ago and I still find little bits and pieces of info to use. Also, it's important to know how much vacuum your motor pulls while in gear for proper power valve selection. I have my 750 set up with a 6.5 valve in the front (motor pulls 14 inches vacuum) and plugged PV in the rear with a 8-10 step up jet size on the secondary side.

  4. APEowner

    APEowner Veteran Member

    Dec 9, 2013
    Albuquerque, NM
    Frankly, I think you're better off getting QJet tuning tips. It's a much better carb for the rest of your combination and if you can't get a relatively simple carb like a QJet tuned correctly it's going to take you forever to get the Holley to run right. There's just so much more to adjust, and therefore have out of whack, on the Holley.
  5. Quadrajet Power

    Quadrajet Power Member

    Feb 19, 2015
    Waring, Tx
    I agree with the Quadrajet being best for driving and performance for you when they are set up correctly.

    For the Holley, you can replace gaskets, floats, needle/seats and give it a shot. You can adjust how quickly the secondary side comes in for you also.
  6. MagicRatt

    MagicRatt Veteran Member

    Aug 24, 2004
    Southampton, Pa.
    I've used both style carbs over the years (36 of them) and have had success with both. I prefer a Holley because of how simple they are to tune, not to mention the amount of parts, jets, gaskets, knowledge I have collected over the years. If you want to invest some time and resources, give it a try. A Q jet will work fine (if tuned correctly) on the street for everyday use. One other thing to consider is your intake. Try to stick with a dual plane design if you can. Also, a future gear swap to a 3.55 or 3.73 would give you some pop in the seat of your pants. This reminds me of the early 80's with my 67 chevelle and always trying different combo's to try and get everything out of a mild 350. Ahh, the good ol days.......


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