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Stromberg 97 Guru needed!

Discussion in 'The Hokey Ass Message Board' started by WasteGate, Dec 4, 2007.

  1. WasteGate
    Joined: Apr 1, 2007
    Posts: 21

    WasteGate
    Member
    from Houston

    The setup:
    I have 6 Stromberg 97's on a 871 blown 427 (Long laundry list of go fast parts).
    The problem is I cant get the idle down below 1200rpm. Granted that is livable. but I would like to have the idle about 700rpm so you can hear the cam talk when I open the exhaust.
    I disconnected all the carb linkage and backed the idle screw completely off and the lowest it will idle is 1200rpm.
    I have spent hours with a UniSync adjusting the carbs and have them all within a 4 point spread. They are running at about 14 to 18 atmosphere, with each bank running the same. The air/fuel ratio runs 13.4 on the driver side and 14.6 on the passenger side. This tells me (A novice) that the A/F mixture is right. I can lean it out but the headers start to glow at idle.
    I know there is an Idle Jet, but per the Hotrod Co. it only comes in one size. I need to change the main jets (parts on order) because under normal driving the engine is to rich, and from the basic diagrams that I have seen the Idle tube feeds from the main jets. This to me would say that changing the main's will affect the idle. Would that be a correct statement? Maybe not. I am going to pull the carbs off tonight to see if there is anything obstructing the butterflies or if the linkage is binding. I don't think there is, I could be wrong.
    Thanks for the help. If you need more info let me know.
    Wastegate
     
  2. uncle max
    Joined: Jan 19, 2006
    Posts: 901

    uncle max
    ALLIANCE MEMBER

    2 cents.
     
  3. strombergs97
    Joined: May 22, 2006
    Posts: 1,888

    strombergs97
    Member
    from California

    Hello..What happens when you put a load on it...does the RPMs drop..I think 1200 is good with that kind of air and fuel..Max is right about the throttle shafts.Spray some carb cleaner on the shafts and see what happens to the idle..Spary it every where you could get a vacuum leak..
    4 cents..
     
  4. WasteGate
    Joined: Apr 1, 2007
    Posts: 21

    WasteGate
    Member
    from Houston

    Uncle Max
    Thanks for the reply. The 97's are the new ones. All the gaskets are new and I tried the carb cleaner trick already and the idle stays steady, which tells me I don't have a vacuum leak. I contribute the difference to the Blower. it evidently pulls harder on one side. Which would lean out the other (thats my guess). Have you ever ran a roots style blower with multiple carbs, and were you able to get both sides running even?
    I have yet to pull the carbs off to see if there is any binding. I will probably do that tomorrow since it wont be as cold out.
    I sent an email to Clive at Stromberg-97. He says the new Idle jets are .031, but has a set of old jets that are .027. I'm not to concerned about the A/F difference between sides, under accelerating load and hard acceleration the AF evens out. Im trying to get ready for some dyno pulls and want to be at least near the ballpark when i get there. Our club is going to video the dyno pulls and post them on the internet. I will put a link up with the numbers. When we do the hits.
    Thanks for the insight.
    Strombergs
    When it is in gear it only drops about 500 rpm. and there is no difference in the AF. I have a built TH400 with a 2800 stall so it does not move much in gear until you crack the throttle.
    Thanks for the reply's
    Wastegate
     
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  5. ratstar
    Joined: Feb 22, 2005
    Posts: 1,313

    ratstar
    Member

    Listen to uncle max he knows them inside and out!
     
  6. WasteGate
    Joined: Apr 1, 2007
    Posts: 21

    WasteGate
    Member
    from Houston

    Ok so I pulled the carbs off last night and found that when the Power valve was set to the Winter setting the carb would not shut the butterflies completely (Found this on 4 of the 6 carbs). I could have put a bigger spring on them, but that would have made the petal uncomfortably stiff! When it was set on the Summer setting you could physically tell tell a difference. There is no doubt that the butterflies close now. I will put it back together after I get some different Main jets. I'm not going to touch the idle jets because I can get the A/F mix set to an acceptable range at idle.
    This would also explain why I could not get both sides to run the same.
    See you on the road soon!
    Wastegate
     

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