Carb tuning ??

Discussion in 'Engine Topic' started by Aceshigh, Apr 3, 2010.

  1. Aceshigh

    Aceshigh Veteran Member Lifetime Gold Member

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    My rocket 350 ran fine before I rebuilt my Holley 1850 (4160) 4 barrel Vac Sec carb. I rebuilt it for the educational experience at the end of last season. Now it's Spring and I'm trying to start the car and tune the carb. Not having alot of luck. I'm pretty sure I used the same size power valve and jets in this.

    I got a vacuum gauge hooked up to where the full vacuum line is under the front bowl. This vacuum line is usually connected to a vacuum canister on my firewall in my Olds 442. When I can get the car started I have to keep my foot on the pedal to keep it alive. The idle mixture screws are 1.5 turns out from the start. If I adjust them 1 full turn counterclockwise (more open) I'm not seeing any changes in my vacuum gauge OR in the idle. THe car still refuses to stay running on it's own without me holding the pedal down.

    I get about 13 on the Vacuum gauge with my foot keeping the car alive via pedal.
    I don't have a tach in the car so I don't know what EXACT RPM I'm at.....maybe 1100-1500 tops.

    I've watched both these video's and I'm not sure what else I can do.
    Any input is appreciated.

    How To: Setting Idle Mixtures
    How To: Setting Curb Idle Speed
     
    Last edited: Apr 3, 2010
  2. hhott71

    hhott71 R.I.P 11/19/18 Lifetime Gold Member

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    I'm sure you've checked the obvious things like Ignition timimg and for a vacuum leak etc.

    You may have had a bug crawl in an air bleed. A quick way to clear them is with high engine vacuum.
    Here is how to do that, Get a shop towel in your right hand and open the throttle with your left enough that it seems to be 1500-1800 rpm or so.
    Now smoother the carb primaries opening with the your towel wrapped right hand, as you do that open the throttle further.
    If it works it was a dead bug-dirt in an air bleed. If not it cost you 30 seconds of time.
     
  3. Rick WI

    Rick WI Veteran Member

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    Is the choke setting correctly when cold?
     
  4. Aceshigh

    Aceshigh Veteran Member Lifetime Gold Member

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    I am not sure what the EXACT choke setting is since I put on an electric choke.
    I didn't hook up the wires yet and was doing it manually.....I kept the choke plate open about maybe 1/8-1/4"

    I tried it wide open too, mind you this was on a 70 degree day....didn't think the choke would play a factor much
    but like I said, I'm not really knowledgeable with carbs at all. I'm shooting in the dark here.

    Ignition timing wasn't touched. So I am just assuming since I touched the fuel portion, it's gotta be the carb.

    Vacuum leak?? Honestly, I'm not too savvy on this aspect. So no, I didn't.
    I just disconnected what hoses went to the carb , rebuilt it, reconnected everything.
    All hoses were labeled so I didn't mix them up.

    I'll try the bug deal though because my hoses WERE uncapped while I was doing the carb, so that's possible.

    When you say "Smoother the carb primaries" .....are you saying cover the primaries with a towel over my hand WHILE I open the throttle more?
     
    Last edited: Apr 4, 2010
  5. Dave Nelson

    Dave Nelson Veteran Member

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    Ace , when you rebuilt the carb did you blow all the passages out with air? Sounds like you have some crud blocking one or more of them. Before taking carb apart again spray some 2+2 carb cleaner in the idle air bleeds they can clog easily. If everythink was ok before you rebuilt the carb you could possibly have the wrong metering block gaskets or they may be installed incorrectly.
     
  6. hhott71

    hhott71 R.I.P 11/19/18 Lifetime Gold Member

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    Yes as the engine is losing speed from being smothered, that way you have 350cu in trying to suck you thru the carb. It'll dislodge any dead bug carcass and its cheap and easy to try.
     
  7. muscl car

    muscl car Veteran Member Lifetime Gold Member

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    there's something definately wrong as you've only got 13"hg vacuum at 1300rpm .............. you should see alot more vacuum than that !!!:eek::eek: . any motor should start right up and idle nicely with the a/f screws at 1 to 1-1/2 turns out
     
  8. Aceshigh

    Aceshigh Veteran Member Lifetime Gold Member

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    Alright, so I'll disconnect all the hoses and blow them out with air just in case any bugs got in them.

    Thanks for that suggestion.

    I blew EVERY passage out 2x with 120lbs of compressed air.

    As for the proper metering block gasket.....I matched it up with the old one.
    I'm pretty sure I only got one primary metering block gasket with the kit.
    I have another secondary one, but it's brown and both the one's I put on were blue IIRC.
    It's possible I made an oversight there.....but I'm pretty sure i checked that 2x as well.

    This is the carb rebuild kit I bought Part # 37-1542 which is says is for 4160 models and mine is an 1850 4 barrel Va secondary which is a 4160
     
    Last edited: Apr 4, 2010
  9. Aceshigh

    Aceshigh Veteran Member Lifetime Gold Member

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    Okay.....so something is definitely blocked then.
    I guess I gotta rip it apart again....dammit.

    Thanks guys.
     
  10. Dave Nelson

    Dave Nelson Veteran Member

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    Before you take it apart , spray the idle air bleeds , and take a fine strand of wire to insert in the bleed hole.
     

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