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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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mo balls than $cents$
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11,734 Posts
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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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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Highaboosta
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3,431 Posts
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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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
 

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steelcomp was here
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26,512 Posts
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.
 

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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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