Holley Jets
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Joined: Sep 2004
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From: Minnesota
Holley Jets
I have a Speed Demon that Lars had setup. He changed the primary jet to 65 and the secondary jet to 72. The original jets were #62 and #70. Now the confusing part. When I look at Holley's website they list the part number 122-62 as being .061 jet size and the 122-70 as being .073, which I'm assuming are the part numbers for the original jets. So, when Lars say's the the new jet's are 65 and 72, is that the jet number or the jet size? Because the 122-65 would be .065 jet size and the 122-72 is a .079 jet size. I don't see a .072 jet size. So I would guess that the new jet part numbers would be 122-65(size .065) and 122-72(size .079).
Holley Website:
http://holley.com/search.asp?query=c...eModel=&page=5
The reason I'm asking is that I need to increase the jets now that I changed the cam and heads and I need to know where I'm starting. I'm thinking that I need to go up 1 size but the Holley numbering system is confusing.
Holley Website:
http://holley.com/search.asp?query=c...eModel=&page=5
The reason I'm asking is that I need to increase the jets now that I changed the cam and heads and I need to know where I'm starting. I'm thinking that I need to go up 1 size but the Holley numbering system is confusing.
Last edited by captainmorgan; Sep 1, 2008 at 10:49 AM.
Melting Slicks
Joined: Dec 1999
Posts: 2,116
Likes: 156
From: Mid West
Cruise-In III Veteran
The jet size is stamp on the side of the jet. Don't worry about the actual hole diameter, they don't match up with the jet size. The size is based on flow rate, not diameter.
Also, because of tolerances its usually recommended to go up 2 or 3 jet sizes at a time. The standard jets have a large tolerance and going up 1 size may not yield any change. Holley does sell more precise jets, but they cost more.
Also, because of tolerances its usually recommended to go up 2 or 3 jet sizes at a time. The standard jets have a large tolerance and going up 1 size may not yield any change. Holley does sell more precise jets, but they cost more.
Melting Slicks
Joined: Aug 2008
Posts: 2,200
Likes: 3
From: Lehigh county Pennsylvania
The accepted convention, when talking Holley jets, is to use the number stamped on them, such as #65 or #72.
If you're getting into drilling out jets and need to describe a hole by drill size to a specific diameter, use the decimal as in .073 and the inch " character; .073" Then there's no confusion.
BTW, from this Holley catalog page:http://holley.com/BrowseCatalogs.asp...Holley&Page=87 a number 122-72 is .0755" inside diameter, NOT .0790".
If you're getting into drilling out jets and need to describe a hole by drill size to a specific diameter, use the decimal as in .073 and the inch " character; .073" Then there's no confusion.
BTW, from this Holley catalog page:http://holley.com/BrowseCatalogs.asp...Holley&Page=87 a number 122-72 is .0755" inside diameter, NOT .0790".
Last edited by 69 Chevy; Sep 1, 2008 at 08:30 PM.
