Carb jetting
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Carb jetting

  1. #1
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    Default Carb jetting

    We just put together or new motor and we need to figure out the jetting.

    The motor is 522cuin with dart aluminum heads and roughly 9:1 compression. The cam is a custom solid roller with roughly .650 lift and 116 lobe centers. We purchased a used tunnel ram with dual 750 DP and we're running dry rewards headers. What jets would you start with?

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    S&S
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    I know it sounds cliche, but I've always tried stock jetting as a starting point, especially on used carbs. Just to see where you are really at. Here is a list of most Holley jet sizes: http://www.holley.com/data/TechServi...%20Listing.pdf If it's fat at idle, might try putting a SMALL strand of wire in each of the idle feed restrictors and go from there.

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    We ran it yesterday and it seems pretty close. The only issue we had was a slight hesitation of idle. We never gave full throttle, but it felt good at half throttle, and it idled great as well. I checked the plugs when we got back and it definitely isn't rich, but it's hard to get an accurate reading because we idled it quite a bit getting it back to the ramp.

    i think our plan is to change the cams on the accelerator pumps and go upa couple sizes on the jets

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    Quote Originally Posted by husqy510 View Post
    We ran it yesterday and it seems pretty close. The only issue we had was a slight hesitation of idle. We never gave full throttle, but it felt good at half throttle, and it idled great as well. I checked the plugs when we got back and it definitely isn't rich, but it's hard to get an accurate reading because we idled it quite a bit getting it back to the ramp.

    i think our plan is to change the cams on the accelerator pumps and go upa couple sizes on the jets
    How's the adjustment at the accelerator pump-arm?
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

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    Quote Originally Posted by HammerDown View Post
    How's the adjustment at the accelerator pump-arm?
    X2. Make sure fuel is being pumped out the squirters with even the slightest movement of the throttle blades. If not, most times adjusting the pump arm will get it. Sometimes, simply putting the cam in the number 2 position will get it where it needs to be.

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    it looks like accelerator pumps are working as soon as we touch the throttle, so we may look into larger squirters.

    We bumped up the jets a little as well. Went from 75s to 78s on the primaries, and 78s to 80's on the secondaries. We'll see how that works.

    What plugs do you guys recommend? We're running a supermag III.

    Thanks, Ian

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    Quote Originally Posted by HammerDown View Post
    How's the adjustment at the accelerator pump-arm?
    That was a issue I had once, didn't notice the nut came off and for some reason it kept coming of till I used some lock tight
    With Spray there is a way!!!

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