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What Jets with a Holy 570?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by personaltrainer, Nov 23, 2004.

  1. personaltrainer

    personaltrainer 1/2 ton status

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    I'm in Atlanta (about 1,000ft elevation) and recently put a holley 570 with edelbrock intake on my truck. I do not really like the way it's running (it an improvement but i think I should have gotten more performance than that) and I've taken it back to my mech. to see if he can (again) get it running better. If he has no luck I was wondering if it could be the jets. I've heard of Holly sending the incorrect jets befor. He has a set of jets for it if we need them but I was wondering what #jet came in the 570 orginally and what I would need to switch to for a trial. Any ideas? Thanks.
     
  2. personaltrainer

    personaltrainer 1/2 ton status

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    come on.... no one knows?
     
  3. Thunder

    Thunder 3/4 ton status

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    Nobody much uses Holley here. They are a lousy carb for off road use. Lots of flooding problems
    If you want a offroad(or on road for that matter)Carb.Q jets are the only way to go.
     
  4. TWISTEDJACK

    TWISTEDJACK 1/2 ton status GMOTM Winner

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    What motor are you putting it on a stock 350/305 /forums/images/graemlins/dunno.gif Holley's are not slap one on and go carbs. They need to be tuned to each motor. It is hard to explain how to do it. I would go up at least two sizes to start with.
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    He needs to go leaner on jets if he's up in elevation where the air is thinner, not richer.

    I'd go two jet sizes smaller on the primaries and see what happens.

    Don't worry about what's supposed to be in it from the factory, just tune it from where it's at now.

    That is, assuming ignition is 100%.
     
  6. Thunder

    Thunder 3/4 ton status

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    If you are going to re jet a carb the first thing you should do is pull your spark plugs and look at them.
    Their condition will show you if you need to go rich or lean in your jetting. Or maby go to a colder or hotter plug.
    Here is a very good plug chart:http://www.4secondsflat.com/plug_chart.html There is a hell of a lot more to plug reading than what it shows but it does give the basics.
    I have found Most small CFM street Holleys are jetted a little on the lean side. They are a generic carb that comes out of the factory to fit a wide range of engines. I'm guessing your carb is a Holley Street Avenger. Right?
    Before you go messing around with the jets.
    You should check the float level they often dont come set right from the factory.
    If you are getting a bog on acceleration you may need a stronger vacuum secondary spring. you can get a bunch of diferent springs in a kit.
    As above posts say Holleys usually need to be tuned to your engine.
    Sorry if my first post was not what you needed but I am not a big fan of putting Holley street carbs on a 4x4. They simply dont work off road.
    Altho I have heard a lot of good things about their Truck Avenger series carbs.
     
  7. TWISTEDJACK

    TWISTEDJACK 1/2 ton status GMOTM Winner

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    [ QUOTE ]
    He needs to go leaner on jets if he's up in elevation where the air is thinner, not richer.

    I'd go two jet sizes smaller on the primaries and see what happens.

    Don't worry about what's supposed to be in it from the factory, just tune it from where it's at now.

    That is, assuming ignition is 100%.

    [/ QUOTE ]
    I really doubt it if it is on a decent 350 a 1000 ft elevation is nothing. The 600's come with larger jets than the 570 and that is where I start jetting down on stock motors. Also we are assuming that you have the right power valve.
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    [ QUOTE ]
    He needs to go leaner on jets if he's up in elevation where the air is thinner, not richer.

    I'd go two jet sizes smaller on the primaries and see what happens.

    Don't worry about what's supposed to be in it from the factory, just tune it from where it's at now.

    That is, assuming ignition is 100%.

    [/ QUOTE ]
    I really doubt it if it is on a decent 350 a 1000 ft elevation is nothing. The 600's come with larger jets than the 570 and that is where I start jetting down on stock motors. Also we are assuming that you have the right power valve.

    [/ QUOTE ]

    The 600s come with bigger jets because they flow more air to begin with. /forums/images/graemlins/doah.gif /forums/images/graemlins/deal.gif
     
  9. TWISTEDJACK

    TWISTEDJACK 1/2 ton status GMOTM Winner

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    [ QUOTE ]
    The 600s come with bigger jets because they flow more air to begin with.

    [/ QUOTE ] How many Holley's have you tuned??????????? At your young age??? Enuf said
     
  10. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [ QUOTE ]
    [ QUOTE ]
    The 600s come with bigger jets because they flow more air to begin with.

    [/ QUOTE ] How many Holley's have you tuned??????????? At your young age??? Enuf said

    [/ QUOTE ]

    Plenty. /forums/images/graemlins/deal.gif

    My statement is common sense.
     
  11. personaltrainer

    personaltrainer 1/2 ton status

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    okay okay. break it up guys..

    Sorry it took me so long to get back. I went out of town for T-giving. As for Holleys off road - like I said I'm IN ATLANTA and don't get out of town much to actually go off road. Occational hunting or fishing trip or whatever but no hard core wheelin. Mostly city driving for me.

    To answer some questions. It is a 350 and as far as I know the ignition system is fine. I was hoping there would be a "magic" number for the jets that would make it run great - guess not huh? Looks likt there are many variable involved in getting this thing running right. As for the size (570) - that is what my mech recomended for my application - think he's wrong??
    I'll check the plugs when I get it back today and go from there.
     
  12. Thunder

    Thunder 3/4 ton status

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    570 is fine. Acually the ideal CFM for a stock 350 is around 550 cfm so you are great as far as that goes.
    If you mostly use it for the street the Holley should work good for you, Once you get it dialed in
     
  13. personaltrainer

    personaltrainer 1/2 ton status

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    cool. I'm glad to know that - i was scared that my mech was steering me wrong.....
     

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