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Technical Chevy 350 won't stay running unless on half choke

Discussion in 'The Hokey Ass Message Board' started by Tex Flick, Sep 30, 2017.

  1. Tex Flick
    Joined: Sep 30, 2017
    Posts: 29

    Tex Flick


    So, I have a '59 GMC with a Chevy 350 in it (My Grandpa put the 350 in it years ago) with a Holley 4412 2 barrel carburetor that I'm having some issues with. I'll start from the top so you guys know the history: This pickup has sat for at least 10 years. I decided I was going to get the thing running one day and I couldn't get it to run. So I took the carb off, bought a rebuild kit for it, cleaned it and put it back on and still wouldn't run. I came to the conclusion that it was the fuel pump not getting fuel to the carb, so I put a new pump on and it started after priming it. Now, it won't run unless it's on at least half choke. I've messed with a lot of carbs on 3 wheelers and 4 wheelers and motorcycles, but never a 2 barrel Holley before. If any of you could shed some light as to what's going on that would be much appreciated.

    chryslerfan55 likes this.
  2. the base gasket may be leaking. Way too much air coming in
    rfraze, dan c and chryslerfan55 like this.
  3. Tex Flick
    Joined: Sep 30, 2017
    Posts: 29

    Tex Flick

    I don't think it's that that was one of the first things I checked.
  4. Tex Flick
    Joined: Sep 30, 2017
    Posts: 29

    Tex Flick

    Could it be some of the old gas that's in it? I know there was a quarter tank (if the gauge is right) of 10-year-old gas in it before I topped it off with fresh.
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  5. upspirate
    Joined: Apr 15, 2012
    Posts: 2,191


    I'd drain, flush, and fill with new....easy to eliminate that area.
    Sounds like one or some of the passages/air bleeds are still blocked.
    I had a guy rebuild a carb for me once that was off a running S-15 truck that he said took 3 days of soaking in good cleaner before all the passages came clean and throttle blades unstuck. I'd been driving that vehicle for 4 yrs and never realized the secondary (2 bbl) was stuck shut.....just thought the lack of power was due to the 1.8 small 4 cyl engine
    clunker and Tex Flick like this.
  6. krgdowdall
    Joined: Apr 3, 2015
    Posts: 102

    from Alberta

    Did you change the fuel filter? The 4412 has a cindered brass filter in the inlet, that usually isn't included in a rebuild kit. It can look good but be plugged. Does the truck have an in-line fuel filter on it? I have seen the paper type filters dry out and collapse causing fuel starvation.
  7. Truck64
    Joined: Oct 18, 2015
    Posts: 4,056

    from Ioway

    Sounds a little like the carb is needing cleaning out again? Old varnished fuel is nasty stuff. All those air bleeds and tiny orificeseses have ta be clean.
    upspirate likes this.
  8. I had a 283 doing the same thing. I pulled the intake manifold and resealed it.

    Problem solved.
  9. rfraze
    Joined: May 23, 2012
    Posts: 2,003


    Vacuum leak. Spray starting fluid lightly around intake and carb until it revs up, indicating where leak is.
    Fordor Ron and sunbeam like this.
  10. Tex Flick
    Joined: Sep 30, 2017
    Posts: 29

    Tex Flick

    Thank you all for the suggestions, I will try them when I get home from work.
  11. I have had past experiences with a stale batch of fuel or a fresh can of bad gas station fuel requiring lots of choke to keep the engine running, but clearing right up with a fresh batch from another gas station.
    Yes, a bad batch of fuel would be the first thing I would eliminate before digging into other things.
    Yes, ditto on looking for vac leaks from cracked hoses etc.

  12. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,222


    Gas turns into varnish and plugs everything up. The tank needs to be thoroughly cleaned out/sealed, the pickup sock replaced, all the lines cleaned/flushed, and all new rubber connecting hoses replaced. To clean out metal fuel lines, I've used an old speedometer cable (the inside cable), chucked into an electric drill, and run it in/out, followed by flushing. The cable is flexible enough to make it through most fuel line bends. Almost all new gas has ethanol in it, that is hydroscopic, meaning it absorbs moisture, so you want to use an additive such as Stabil, to help prevent future rusting due to moisture. New fuel filters, and rebuilding the carburetor again (due to old gas/crud) are needed. If you want to use a remote gas tank, like a boat gas tank, just to see if it improves things, would't be a bad idea.
    I am Butch/56sedandelivery.
    upspirate likes this.
  13. dirt t
    Joined: Mar 20, 2007
    Posts: 4,601

    dirt t
    from Kingman,AZ
    1. HAMB Old Farts' Club

    First thought is a large vacuum leak.
  14. midnightrider78
    Joined: Oct 24, 2006
    Posts: 918


    I second this. Old fuel is a royal pita to get thoroughly cleaned out. Also, as an alternative to soaking the carb for days at a time, you may want to see if there is somebody local that can ultrasonic clean it. I have had 2 motorcycle carbs and one atv carb cleaned this way and the difference was night and day. Plus it's fast(less than an hour in these instances), cheap($45 for the motorcycle carbs) and you don't have to worry about chemical clean up or disposal.
    upspirate likes this.
  15. dave lewis
    Joined: Dec 12, 2006
    Posts: 1,358

    dave lewis

    If you are close I can help you clean everything up..
    Betting it's the old gas for sure.
    Putting new gas in the tank on top of the old stuff just thins it enough to cause trouble..
    I've actually experienced ( severs times !) Valves getting stuck and pushrods bending due to the varnish drying overnight..
    Not fun.

    My advice when starting anything up that has been sitting.. clean out the tank FIRST !
    this is the voice of experience talking...LOL

    Sent from my SAMSUNG-SM-G891A using The H.A.M.B. mobile app
    rhtfo and upspirate like this.
  16. upspirate
    Joined: Apr 15, 2012
    Posts: 2,191


    I've had an outboard engine not run right on gas that went stale after only 4-5 weeks.Couldn't get it to start or stay running.When I took the cap off, I couldn't believe how bad it smelled. New fuel ,cranked right up.....this was before ethanol also.

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