Holley Jets, number or hole size?

Discussion in 'Small Block Tech' started by Mark Demko, Sep 2, 2019.

  1. Mark Demko

    Mark Demko Well-Known Member

    I forgot which number is important when ordering.
    I have .080 primary now, I want to go a tad leaner, Im thinking .077
     
  2. 73 Stage-1

    73 Stage-1 Dave

    One jet size is a “tad,” two is a real change. If everything is working well, I’d stick with changing jets two sizes at a time until you dial it it into a single number change.

    Are you reading the spark plugs or have an air/fuel gauge?
     
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  3. Bens99gtp

    Bens99gtp Well-Known Member

    I think 2 number size is about 2%. The number size from holley doesn't not directly mean a hole size as several jets can share the same hole size but have different entry and exit angles effectively increasing or decreasing flow. If the slots get puckered up that too can effect flow size.

    Bigger numbers flow more than smaller numbers
     
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  4. Mark Demko

    Mark Demko Well-Known Member

    A/F gauge.
    Its showing 12.5 12.8 13.0 around town
    Highway (32/3500 rpm) no leaner than 13.5
    Car drives flawlessly, plugs look ok, darkish tan.
    I just wanna lean it a tad, so just go leaner by a couple numbers then?
     
  5. Mart

    Mart Gold level member

    With the dual plane and divider cut down, I ran 77 / 90's on the last setup. With a Wilson 2" tapered spacer.
     
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  6. 69a-body

    69a-body Well-Known Member

    I've been round and round with this. Trying to lean out my carb and watching vacuum readings at cruise. Usually two jets will show obvious changes and you can correct or compromise one back if it is too much. Probably little gain though. 10% ethanol stoich is like 14:1. Ignition timing also determines how lean you can burn. It's a balancing act for sure.
     
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  7. Mark Demko

    Mark Demko Well-Known Member

    Currently I have 80 front 90 rear in my AED on the SP3
    I have absolutely no issues now, but I wanna see how the A/F changes and how the engine responds taking some fuel away.
    BUT, I gotta keep a keen ear for detonation:eek:
    Like 69a-body said its a balancing act
     
  8. Mark Demko

    Mark Demko Well-Known Member

    IMG_4455.JPG IMG_4456.JPG Heres a couple plugs, they look pretty clean/lean already, maybe I shouldn't mess with it!
     
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  9. Mart

    Mart Gold level member

    Fat is safe, lean could be mean....:D
    You could play with timing some.
     
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  10. Mark Demko

    Mark Demko Well-Known Member

    True!
    I think I'll leave the fuel alone, and move the distributor around for something to do!
    Im only at 32/33 total
     
  11. Bens99gtp

    Bens99gtp Well-Known Member

    Looking at those pics you can see the timing line is close to the turn, might be able to go 2 degrees, fuel does look s touch dark on the base ring.......but if adding timing I wouldn't pull fuel
     

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  12. sriley531

    sriley531 Excommunicado

    Those plugs look pretty nice, not sure I'd mess with it Mark. Like others said, a little fat is safe, and since your plugs look so clean I'd be content with that AFR IMHO unless you're at the track chasing every .01 you can. I'd throw a few degrees at it and see what she does.
     
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  13. 69a-body

    69a-body Well-Known Member

    My experience with a Holley has been , once it's tuned the temp changes and you start over. Problem is you need to be a little fat since there is no progressive fuel enrichment until power valve pops. So really it's always a compromise. A well sorted quadrajet in my opinion always will win in efficiency.
     
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  14. Mark Demko

    Mark Demko Well-Known Member

    Good point!
    That's why I ask here, you "more seasoned" guys know better than I do;)
    11 to 1 with iron heads is always in the back of my mind, no issues yet, and I certainly don't wanna create any:cool:
     
  15. Mark Demko

    Mark Demko Well-Known Member

    I think I'll just play with the timing then!
    A theory I have is the looser the convertor, the more timing the engine should tolerate up to a point, being the engine is seeing less load down low, until the convertor starts loading the engine, say 3400 rpm and up, in my case.
    This theory hold any water??
     
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  16. Stevem

    Stevem Well-Known Member

    Holley jets have a pretty good spread of tolerance to them so you should always go 2 numbers different from the way you want to head to a definitive change take place.

    If most of the color time on your plugs is from crusing then leaning the jetting may not buy you much improvement, as you might want to try a .5 higher rated power valve first!
     
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  17. Mark Demko

    Mark Demko Well-Known Member

    I bumped my total to 36 deg. Took it for a ride, didn’t hear any pinging, it’s tough to listen for it as the mufflers are quite obnoxious when you lean into it, also the engine does not run much more than 175, that’s with a 160 T stat, even when it was 90 plus out.
    Well we’ll see what she does next trip to the track, gonna put 5 gals. of 110 in just as Larry suggested at Quaker:D
     
  18. Bens99gtp

    Bens99gtp Well-Known Member

    We are going to Norwalk this weekend....be nice to not be the only buick there.

    You can always use avgas its about 105 octane and only about 5 bucks a gallon. We run it only in out car, have for decades
     
    Last edited: Sep 3, 2019
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  19. Mark Demko

    Mark Demko Well-Known Member

    Whats going on at Norwalk this weekend?
    I "plan" on going to 42 next Friday afternoon for TNT, haven't been there since the remodel.
     
  20. Bens99gtp

    Bens99gtp Well-Known Member

    Nothing special just a sat night. I am going to big no box event there at the end of the month.....so figure I would go get some track time there,

    I've been to 42 on a thursday night and went to the finals and sat a few weeks ago and went to the semifinals, but those are the only 2 times I've been out and still trying to get these shocks dialed in
     
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