Help in reading jet size

surfsup · 01-09-2005, 09:18 PM

I removed one jet to check it’s size and I’m not clear on how to read it on the side it has 612 but the 2 is up side down so is it a 61 jet or a 612 jet I looked in the Holley web site and the carb came through with either one

~The Jester~ · 01-10-2005, 06:38 AM

"Size wise" it's a 61. The upside down 2 is a revision of sorts. I forget exactly what they did to the 2nd version, but what you got there is a size 61 "version 2" type thing.

surfsup · 01-10-2005, 08:13 AM

thanks i want to try a different size

Jeff Chambers · 01-11-2005, 08:06 AM

The 1-2-3 refers to the tolerance of the jet. Each jet is measured and compared to its theoretical perfect sizing. Don't quote me on this, but I think 1 is towards the low limit and 3 towards the high limit on the machining tolerances. Therefore, if you're trying to assemble a set of real close tolerance jets, you'd try to put all '1' in your jet kit. I seem to remember reading about this either on the Holley site or in one of my carb tuning books.

Rev · 01-11-2005, 08:57 PM

They used to just refer to them as "close tolerance" jets that cost a liitle more $$$. Now do they have 3 tolerance levels, LOL. I'm really just asking?

Rev

Jeff Chambers · 01-12-2005, 07:14 AM

I seem to remember reading this somewhere. Will try to find the article/book and clarify but this is how I remember it. I've been wrong before though so don't go out buying all #1's !

01-10-2005, 06:38 AM	#2
~The Jester~ Rat Killer Join Date: Aug 2002 Location: Cold ass Ohio Posts: 1,143	Re: Help in reading jet size "Size wise" it's a 61. The upside down 2 is a revision of sorts. I forget exactly what they did to the 2nd version, but what you got there is a size 61 "version 2" type thing. __________________ d-Con Racing "Nothing fancy, just 347 inches of RAT POISON!" MICE need not apply.....

01-10-2005, 08:13 AM	#3
surfsup Registered Member Join Date: Sep 2004 Location: jersey Posts: 147	Re: Help in reading jet size thanks i want to try a different size

01-11-2005, 08:06 AM	#4
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	Re: Help in reading jet size The 1-2-3 refers to the tolerance of the jet. Each jet is measured and compared to its theoretical perfect sizing. Don't quote me on this, but I think 1 is towards the low limit and 3 towards the high limit on the machining tolerances. Therefore, if you're trying to assemble a set of real close tolerance jets, you'd try to put all '1' in your jet kit. I seem to remember reading about this either on the Holley site or in one of my carb tuning books. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"

01-11-2005, 08:57 PM	#5
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Re: Help in reading jet size They used to just refer to them as "close tolerance" jets that cost a liitle more $$$. Now do they have 3 tolerance levels, LOL. I'm really just asking? Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe

01-12-2005, 07:14 AM	#6
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	Re: Help in reading jet size I seem to remember reading this somewhere. Will try to find the article/book and clarify but this is how I remember it. I've been wrong before though so don't go out buying all #1's ! __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"

01-09-2005, 09:18 PM	#1
surfsup Registered Member Join Date: Sep 2004 Location: jersey Posts: 147	Help in reading jet size I removed one jet to check it’s size and I’m not clear on how to read it on the side it has 612 but the 2 is up side down so is it a 61 jet or a 612 jet I looked in the Holley web site and the carb came through with either one

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