Rejetting for more boost
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Rejetting for more boost

  1. #1
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    Default Rejetting for more boost

    I'm upping my boost from 10% to 17%. Do I have to rejet the carbs [850 holleys]? Pat

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    Quote Originally Posted by Wicked Performance Boats View Post
    I'm upping my boost from 10% to 17%. Do I have to rejet the carbs [850 holleys]? Pat
    u dont mention the sz of the blower?...anyways...there was a thread on here about the same subject & i think the 850's power valves were blocked off & the jets upped to 86-88 squared ...i would start around that point!

    FastRat

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    Blower is 6-71, no power valves, jetted at 82 primaries, 83 secondaries now. Pat

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    pat, on my blown 475(9 to 1 compression) runnin a 6-71 19% i ran 86 squared, no pv's in the rear, 6.5's in frt.. plugs were purdyyyyy

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    Highaboosta Unchained's Avatar
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    Question

    What does the O2 sensor read ?

    Twin Turbo 1800 HP V-Drive lake boat

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    Quote Originally Posted by Trigger View Post
    No one cares about your buddies old antiquated garden hose technology.
    Quote Originally Posted by MAXIMUS View Post
    I think I could run more boost but it's a real hand full right now

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    Hondo Jet blown540's Avatar
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    Quote Originally Posted by Unchained View Post
    What does the O2 sensor read ?
    LoL, seriously though I'm looking for a good price point wide band, my lightning headers allready have bungholes. What's a good unit for spot checking/tuning?

  9. #7
    ptz
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    Quote Originally Posted by blown540 View Post
    LoL, seriously though I'm looking for a good price point wide band, my lightning headers allready have bungholes. What's a good unit for spot checking/tuning?
    fast makes a nice one wide band style for around 5 bills.. might check ebay.
    you could use an egt from autometer for around 130 bills...
    they also do an afr with leds...for a few more skins.

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    Quote Originally Posted by IMPATIENT 1 View Post
    pat, on my blown 475(9 to 1 compression) runnin a 6-71 19% i ran 86 squared, no pv's in the rear, 6.5's in frt.. plugs were purdyyyyy
    Thanks I'll take some jets with me. Pat

  11. #9
    Highaboosta Unchained's Avatar
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    The Innovate Motorsports unit is one of the most popular. I've had mine in the boat for 6 seasons now. It has built in datalogging and more features than you could ever use.
    IMO the days of making a guess at A/F mixtures are long past.

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    Quote Originally Posted by Trigger View Post
    No one cares about your buddies old antiquated garden hose technology.
    Quote Originally Posted by MAXIMUS View Post
    I think I could run more boost but it's a real hand full right now

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    Rejetting should only be required if the carbs are at pretty much the top end of their airflow range, yours shouldn't be. If you have a too rich midrange cruise to get the top end right, add replaceable highspeed air bleeds and go about .004 smaller for starters. Otherwise the carbs will be mostly self compensating. Keep a good eye on your fuel pressure whenever you up the boost. TIMINATOR
    MODESTY IS A CRUTCH FOR THE INCOMPETENT!

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    Hondo Jet blown540's Avatar
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    Good info, thanks guys

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    senior member turbo wog's Avatar
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    once it's too fat, you'll know for sure wich way to go

  15. #13
    steelcomp was here
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    Just went through this on the dyno yesterday. If the jetting is correct now, upping the boost that much won't change it. The carbs only react to the amount of air passing through them as they provide a ratio of air and fuel. Once that ratio is correct, the amount of air passing through the carb won't change that ratio.
    If God is your co-pilot, change seats!
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  16. #14
    Senior Member 500BBC's Avatar
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    Quote Originally Posted by blown540 View Post
    LoL, seriously though I'm looking for a good price point wide band, my lightning headers allready have bungholes. What's a good unit for spot checking/tuning?
    What kind of headers? You don't mean the water jacket bungs do you?

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