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Thread: stacks stumble

  1. #1

    stacks stumble

    Need help tuning hilborn stacks, car idles ok seems to have good response revs clean but when throttle is rapped it blows a cloud of smoke.

    Took car for a road test and stand on it, it takes off and then lays over and dies then picks up and stumbles like a bad misfire.

    I've tried riching/leaning with no luck.

    Any advise on what to try would be appreciated.

  2. #2
    Senior Member RACING JUNKIE
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    Need more info. Injection size, gas or alcohol, nozzle size, and pump size. Hilborns are drop dead easy once you get the hang of them, off the top of my head i would say way too fat. Have you done a leakdown on the barrel valve setting. Hilborn recommends starting at 25% with the butterflys set at .002 open, all the ones i've worked on usually wind up at about 20% when well tuned, i've even seen them to like 17/18%. If you don't have a leakdown tester, roll the barrel valve closed until it stumbles when you bip the throttle, then turn it open turn 1 flat at a time until it doesn't. This will get you close on the barrel valve, the rest is in the return pill.

    JMO

    Zip.

  3. #3
    Engine is 268cu v6 chevy, bowtie heads 14.5:1 and a comp solid roller cam.

    alcohol injection is 2 1/16 b/fly with kinsler p510as nozzles, 80a-1/2, 140 pill, 100 h/s.

    when i first started leak was set at 20%, b/fly's were at .005 now look to be about 8-9, i'd have to recheck settings to be sure.

  4. #4
    Senior Member RACING JUNKIE
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    While you're checking, check the HS bypass pressure set it too to 60 lbs. I'm not a fan of useing a pill in the HS, but i know it's a Kinsler setup that does this. Most nozzles like 60/65 lbs pressure to dispurse the fuel properly. Hilborn flows theirs at 65 lbs. when they rate the flow. Too be honest with you the nozzles are pretty small for alcohol, they're border line between gas and alcohol. I realize that the injection is only 2 1/16", example we run 18AS with 2 3/8 and 2 7/16" injection a friend run a 350 sprint car and 2 3/16" and runs 18 AS nozzles. Below is a chart for cross ref. of Kinsler, Hilborn, and Enderle nozzles. Yours cross over to a 12AS Hilborn, this might be a problem, if you have any available try a larger nozzle. It takes lots of alcohol on the bottom end under load, and then the HS leanout takes over, we also run -1/2 pumps.


    Zip.


  5. #5
    Senior Member MASTER BUILDER
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    Hey Zip, That Sprint car has a 305 and not a 350 my motor is a 350 and between you and Melvin and me a little it is deadly,I mean deadly. Later J.Smith 4621 racing :lol:

  6. #6
    Hey Zip my settings were a bit off, about 32 leak and 9 on the b/fly's. I'll reset it and start again toomorrow. The nozzle size is what hilborn recommended(12as), i'll have to buy more if you think i should go bigger.

  7. #7
    Senior Member MASTER BUILDER
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    qiksix, Not trying to but in on Zip, he is still in bed you know he is OLD, When you change those settings it's gonna make a diff. Zip and I are good friends and he has helped me with tuneup on my stacks also a sprint car friend set them up for me . Later J.Smith 4621 racing

  8. #8
    Senior Member RACING JUNKIE
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    Quote Originally Posted by qiksix
    Hey Zip my settings were a bit off, about 32 leak and 9 on the b/fly's. I'll reset it and start again toomorrow. The nozzle size is what hilborn recommended(12as), i'll have to buy more if you think i should go bigger.
    If you talked to Don Enriqes at Hilborn and he recommended 12AS's i would never second guess his recommendations, he is definately the Hilborn Guru. I've know him for yrs. and have talked hrs. with him on the phone and emails. In my opinion there are 3 or 4 EXPERTS in the stacks injection field, the other 2 are Mark Kinsler, and if you want to run a little juice/nitro Spud Miller. There's lot's of people that know how to tune them, but these guys are standouts. I've been tuning stacks and running blown cars for 45 yrs. but everytime i talk to either of these guys i learn something. when it comes to blown alcohol, its Mert Littlefield and Ralph Gorr.
    With that said, make sure you keep the butterflys at .002, anything more than that you'll milk the oil on idle, it needs to idle lean or you'll have to run an idle bypass, if you want to do that set it at 15lbs or less.
    The reason i recommended larger nozzles is, if you had 8 clyinders it would equal bigger than a 355" motor. I've never ran a 2 1/16" system but have tuned a couple, but they were on gas.
    Jimmy Smith, posted earlier, he has a set of 2 7/16" with 18AS nozzles. I used to own that injection and in fact made it into a 3 piece setup. Sat. nite he went 6 rounds and had 4--.698's, sun nite he went to the semi's in the .700 class. A tough,tough class, he qualifed #6 with a .7007, and broke out with a .69999, never had worse than a .702. Now this is a 3200 lbs car with a 355" with 13" slicks, with stacks on alcohol. That guy called me old in his post, :lol: He's 66 yrs. old and i'm 70 almost 71. Good thing i moved from Batesville Ms. to La. i can't wait to meet him at the tree, i'm gonna saw it down on him :P
    A little patience and we can work this thing out.

    Zip.

  9. #9
    Yeh pretty sure it was Don i emailed. The idle bypass the poppet from the rear of barrel valve, yes it's at 10psi. You mention to keep the idle lean but doesn't that hurt throttle responce, i thought it had to be fairly rich for the transition from idle to flat chat.

  10. #10
    Senior Member RACING JUNKIE
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    Not trying to but in, but I'm curious. What is the flow on an 80a-1/2 pump?
    No matter where you go, there you are.
    **IN GOD WE TRUST**


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