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Carb adjustment for mile high running?


rockitdoc

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If it is a newer fuel injected unit, it will probably take care of itself.

If an older carbureted unit, different carburetor manufacturers had suggestions for altitude adjustments. Typically, with the lower energy content of E-10, the adjustment seems just about right for what would be one size lean on real gasoline.

More information on what you have would help in formulating a more precise answer.

Jon.

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Your '41 carb originally came with #54 main jets and a 7.5"hg power jet. This jetting was supposed to be good up to 5000 ft. Many reconditioned carbs and 4 bolt versions were equipped with #57 main jets and these would probably run a tad rich at your elevations. suggest you check to see what you have? Leaner main jets ,#52 or #53 along with a "leaner" power jet, 6.5" hg would probably be ideal for you. These parts are available thru Charlie Price at Vintage Speed along with complete repair kits.

Slower burning modern fuels may also contributes to seemingly overrich mixtures in older low compression engines.

Edited by peecher (see edit history)
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Your '41 carb originally came with #54 main jets and a 7.5"hg power jet. This jetting was supposed to be good up to 5000 ft. Many reconditioned carbs and 4 bolt versions were equipped with #57 main jets and these would probably run a tad rich at your elevations. suggest you check to see what you have? Leaner main jets ,#52 or #53 along with a "leaner" power jet, 6.5" hg would probably be ideal for you. These parts are available thru Charlie Price at Vintage Speed along with complete repair kits.

Slower burning modern fuels may also contributes to seemingly overrich mixtures in older low compression engines.

Thanks Peecher. I'll take it apart and find out what's in there. I assume it's stock, but I just don't know.
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Be sure to check the "old" power valve for leaks. These devils are notorious leakers if "old" and modern fuel has been used. Gas dampness in the cavity below the power jet in the carb body is a sure indicator. A leaking Power jet will indeed make the engine run rich.

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  • 1 year later...

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