Verifying Holley Jet Sizes
Thread Starter
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Verifying Holley Jet Sizes
A few days ago I was checking some of my Holley jets and discovered several that weren't stamped correctly; #70s that were actually #72's, #72's that were actually #74's, and #74's that were actually #76's. Before screwing in Holley jets I recommend you verify their actual sizes by measuring them with number drills.
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Intermediate
Joined: Jul 2010
Posts: 49
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From: Grand Rapids Michigan
Holley categorizes jets by flow, not actual jet size. The chart shown is reference info and indicates the nominal size typically associated with jets in the specific numbered category. However, entrance condition, orifice finish, length, exit condition, and specific size within the tolerance can influence the actual flow a jet will produce. That's why they flow them and then stamp the number.
Re-sorting jets by measuring with drills has a higher probability of error than Holley marking the jets incorrectly.
Re-sorting jets by measuring with drills has a higher probability of error than Holley marking the jets incorrectly.
Melting Slicks
Joined: Jun 2011
Posts: 3,114
Likes: 598
Holley categorizes jets by flow, not actual jet size. The chart shown is reference info and indicates the nominal size typically associated with jets in the specific numbered category. However, entrance condition, orifice finish, length, exit condition, and specific size within the tolerance can influence the actual flow a jet will produce. That's why they flow them and then stamp the number.
Re-sorting jets by measuring with drills has a higher probability of error than Holley marking the jets incorrectly.
Re-sorting jets by measuring with drills has a higher probability of error than Holley marking the jets incorrectly.
Once I got the AFR range and proper color on the plugs I was good to go. The numbers are useful only to know what AFR I got with the specific numbered jets.
