carbs

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  #1  
Old 01-06-14, 11:46 AM
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Question carbs

i have a holley carb 4 barrel the list # is 6772-2054 on a 4150 i think is what kind of carb it is. any help on what kind of jet i should use in the denver area? the stock jets are #66 and i get around 6 mpg with a 390 bob to 402 on an f100 1971. any help
Thanks Matt
 
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Old 01-06-14, 11:51 AM
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Welcome to the forums Matt!

I can't help you with the jets but I used to have a Bronco with a 460 that got 6 mpg I tweaked the adjustments on the carb and timing and was able to get it up to 8 mpg.
 
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Old 01-06-14, 12:27 PM
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A search for "holley carb jet recommendations" gave some good info. Reading the plugs or using a sniffer in the tailpipe will need to be done. Too lean and you will go to 0 miles per gallon as you redo the engine.
 
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Old 01-06-14, 12:34 PM
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Likewise, my 1970 F150 with 460 got about 6 mpg. As far as jets, you need more fuel than air since you don't breathe real air out there anyway i really think tweaking what you have may work. It will just be a richer mixture.

Daughter lives in Highlands Ranch, and we just left, so I know about the air,
 
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Old 01-06-14, 12:48 PM
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In the thin air...you need to reduce the jets to keep a good air fuel ratio. Rich mixture means wasted gas. I guess a rule of thumb is one jet size below stock for each 2000ft above sea level. Thats assuming the carb still has the original jets calibrated at sea level and 70 degrees. Still need to read plugs.

Also a good idea to go through the whole power valve, accelerator pump calibration as well.

This looks like a very good info source...FAQ Rejetting Holley Carbs
 
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Old 01-06-14, 02:10 PM
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Had it backwards. Thanks Vic. Need more air. But, then, your octane ratings are much different.
 
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Old 01-06-14, 06:17 PM
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you reduce the AREA of the jet 2% for every 1500 feet you are above sea level.
 
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