Holley 1940 Main Metering Jets
Don't ruin your engine. Printed specifications for jets were printed many years before the introduction of ethanol so you need to use trial & error to get the correct jet size. Test by looking at your spark plugs. Gray burning plugs are good, black is too rich, white is too lean. Change 1, or 2 jets sizes and repeat the test.
These jet sizes assume 0-5000 feet in elevation. For 5000-10000 reduce by 2, for 10000-15000 reduce by 4.
Some Holley jets were marked using 3 digits. Example 630 would equate to .063. Part numbers below denote the orifice size with the third digit, 120-40-63 = .063"
These jet sizes assume 0-5000 feet in elevation. For 5000-10000 reduce by 2, for 10000-15000 reduce by 4.
Some Holley jets were marked using 3 digits. Example 630 would equate to .063. Part numbers below denote the orifice size with the third digit, 120-40-63 = .063"
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1/4" thread Custom Assortment. You choose 8 different sizes.
Part Number 120-40A
(1)
$55.00
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1/4" x .040"
Part Number 120-40-40
$5.95
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1/4" x .041"
Part Number 120-40-41
$5.95
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1/4" x .042"
Part Number 120-40-42
$5.95
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1/4" x .043"
Part Number 120-40-43
$5.95
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1/4" x .044"
Part Number 120-40-44
$5.95
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1/4" x .045"
Part Number 120-40-45
(1)
$5.95
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1/4" x .047"
Part Number 120-40-47
$5.95
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1/4" x .048"
Part Number 120-40-48
(1)
$5.95
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1/4" x .049"
Part Number 120-40-49
$5.95
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1/4" x .050"
Part Number 120-40-50
$5.95
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1/4" x .051"
Part Number 120-40-51
$5.95
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1/4" x .052"
Part Number 120-40-52
(1)
$5.95
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1/4" x .053"
Part Number 120-40-53
(1)
$5.95
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1/4" x .055"
Part Number 120-40-55
(1)
$5.95
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1/4" x .056"
Part Number 120-40-56
(1)
$5.95
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1/4" x .057"
Part Number 120-40-57
(1)
$5.95
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1/4" x .058"
Part Number 120-40-58
$5.95
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1/4" x .059"
Part Number 120-40-59
(1)
$5.95
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1/4" x .060"
Part Number 120-40-60
$5.95
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1/4" x .061"
Part Number 120-40-61
(1)
$5.95
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1/4" x .062"
Part Number 120-40-62
$5.95
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1/4" x .063"
Part Number 120-40-63
$5.95
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1/4" x .064"
Part Number 120-40-64
$5.95
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1/4" x .065"
Part Number 120-40-65
$5.95
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1/4" x .066"
Part Number 120-40-66
$5.95
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1/4" x .067"
Part Number 120-40-67
$5.95
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1/4" x .069"
Part Number 120-40-69
$5.95