Jet size markings
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Jet size markings

  1. #1
    AARP Member Rocket-J's Avatar
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    Thumbs up Jet size markings

    Holley's marking system does not follow the actual jet size, which is fine if you use only Holley jets. Some manufactures mark their jets with the actual sizes, so unless I have purchased the jets myself, I see no way to know the size. I have not found any measuring tools.
    Any advise out there? Al

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  3. #2
    058
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    Al, Holley sizes their jets by flow, not hole dia. Std. Holley jets have a flow variation of about 3% so that can mean a #80 jet can flow the same as a #79 jet if you stack the factory tolerances. Jet changes are usually made in 2 step increments to get past this variation. Get a book that has the Holley jet listing by numbers such as "Super Tuning and Modifying Holley Carburetors" ISBN # 0-931472-08-3 by S-A Design. Pg. 46 has std. Holley jet listing & hole dia. and close limit jet listings as well.

  4. #3
    cfm
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    If your looking for the Part# and orifice size look here:
    http://www.holley.com/types/Jets%20a...r%20Bleeds.asp

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  6. #4
    gn7
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    This one of the problems using non Holley jets, some suppliers just drill them to whatever hollley says they are and leave them at that. If you look at some holley supplied jets you may see little champhers on one side or the other on some but not all jets, even of the same size. This is how holley trims the FLOW, as 058 stated, they are flowed not just drilled, so to answer your question, you really can't compare some one else's jets to any one else's and be certain of the variance. Comp Cams Max jets are a totally diff deal and are sized by the actual drill size. As 058 also stated, the only way to be certain you are really making a jet change using virtually anybodies jets, is to make a change of a least 2 sizes due to tolerances unless you are using holley TIGHT TOLERANCE jets that come in sets of 3 and have a low, med & hi flow for the same jet size, but they are a little spendy. A little long winded but I hope this helps



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    AARP Member Rocket-J's Avatar
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    Thumbs up Thanks Guys.

    It sounds like I should get rid of my older jets, that I am not sure of thier brand, and only by Holley. At least then I would know if I did indeed make a change or not. Thanks. Al

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    Default jets

    Holly has a great set of jets. from #64-#99, two of each size. Summit for $38.95. hard to beat the price

    Jerry

  9. #7
    gn7
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    Quote Originally Posted by billet racing View Post
    Holly has a great set of jets. from #64-#99, two of each size. Summit for $38.95. hard to beat the price

    Jerry
    and if you don't need that wide an assortment you can always sell the ones you'll never use. Ill buy the 90-99, let me also add that most jets are Holley jets sold to distributors who then but there name on them, but you just never really know.They are just too expensive manuf. just to try and undercut Holley



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    Last edited by gn7; 03-17-2008 at 08:12 PM.

  10. #8
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    You can always use Comp Cams line of Max Jet. These jets are marked in thousandths according to orifice size. They allow you precisely tune the metering circuit. Numerous Holley jets in different sizes are actually cut and finished with the same reamer giving the end user a false sense of flow.
    Repeat, Repeat. Sorry Al, should of read your whole reply.
    FLATTIES ARE FOR DRIVERS; ALL OTHERS ARE FOR RIDERS!!!! M AND D PERFORMANCE / WHITE TRASH Team Wet Dream

  11. #9
    AARP Member Rocket-J's Avatar
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    Default That's the problem, WT

    WT
    It is very easy to mix up the accuratley marked jets with the Holley jets. I really don't care if they put the alphabet on each jet, as long as I know where I am and where I am going. Thanks for the info.
    Billet
    Jeg's has a Holley jet package of 11 pairs for $15.
    i.e. 70 to 80 kit
    80 to 90 kit
    90 to 100 kit.
    All come in a case. Great price.
    gn7
    It's the larger ones that I need. I have lots of small ones. Want a bracelet?
    Thanks again for all the help. Al

  12. #10
    gn7
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    thats where most people make the mastake, assuming that they number on them is in any way based on the bore size like the max jets are. Holley jets are numbered by FLOW which means that two numbers can have the same bore size and yet flow differently, confusing, yes. But once you understand their system it doesn't much matter.



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  13. #11
    058
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    Only use Holley jets in a Holley. If you go by hole diameter you will chase your tail. It was said time and again Holley jets are rated by flow not hole. Example: a #80 jet has the same size hole as a #81 and #82, all .093" hole dia. and a #83 is only .001" bigger @ .094" but the next number is a #84 which is a .099" dia. hole. edit: One more thing Al, do NOT drill a smaller jet for more flow, not only this will render the number on the jet useless and unless you have a memory that would make an elephant proud you cannot commit it to memory and a drilled jet will totally screw up the fluid flow thru the jet. In other words a larger hole can flow less than the orig. hole. Holley goes to extreme measures to finish machine the entry and hole surface of the jet.
    Last edited by 058; 03-17-2008 at 09:17 PM. Reason: Edit to add:

  14. #12
    gn7
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    I would say that pretty much drives the point home right there. Hell I wish I would've said that



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  15. #13
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    Quote Originally Posted by gn7 View Post
    I would say that pretty much drives the point home right there. Hell I wish I would've said that
    Hell....I was hoping to turn this into another Prop nut thread.... Its been a long winter.

  16. #14
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    Quick side question.

    I have a couple jets that have an "H" on them. I think they say 80H. What does the "H" mean?

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