AVS2 compared to Street Demon?

Fuel and Air Systems

  1. 7milesout

    7milesout Well-Known Member

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    68 Coronet RT - I don't mean to sound snobbish. But with my spreadsheet that calculates EVERY SINGLE ROD AND JET COMBO available, which allows precise jetting data to be compared to all other available rod and jet data, which correlates extremely close to my readings on the AFR gauge, there is no better rod / jet primary or secondary jet size available that would make an improvement.

    And watching the AFR gauge under all circumstances, the only way to improve this slight off idle stumble would be at the sacrifice of some other currently great driving aspect. As I've mentioned, I've got this tuning down to an art (at least for Edelbrock carbs). Under all circumstances (except this off idle stumble), the car drives flawlessly. Any change to my current jetting would yield poorer drivability. It is maxed out given the mechanical limitations of the rods and jets available.

    It's so good in fact that if anyone here has a mildly warmed up LA 360, I would be happy to share my rod/jet main and secondary set up. You could try it and see if it doesn't make your overall street and WOT performance better. I'm counting on the switch to the annular boosters to clear up this lean stumble. I've read that it does just that.


    7milesout
     
  2. 68 Coronet RT

    68 Coronet RT 68 GTS # 508 in Registry

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    Well all I can say is if all your spreadsheets and what ever you have says you are good I don't know what to tell you if you haven't at least tried something other than what your sheets and AFR are telling you. All I know is I had the same issue with my brand new 650 AVS-2 and everything was telling me it was perfect and all it turned out to be a timing issue. Why don't you take the time and call the Edelbrock Tech line and talk to them.
     
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    • 7milesout

      7milesout Well-Known Member

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      I've tried LOTS of different jets and metering rods. Until I wised up and made the spreadsheet. I only made the spreadsheet to reduce the guessing and iterations of changing things. It's not perfect, but it and the AFR gauge are very in-sync. So, it has eliminated iterations of changes. It also clarifies to me with data, what any little change of metering rod and/or jet from where my carburetion is now, will go. In one way or the other, it would be worse if I made any changes. Meaning, my carburetion is optimized. No perfect, but optimized based on available metering rods and jets. I have also designed a metering rod that would improve my current carburetion but I haven't been able to find a company that could / would make these rods. At least, at a reasonable cost.

      I did call the tech line and talked to them about this stumble. They were not helpful. As I guess this is a well documented issue with this carb, and is at least partly the reason for the annular boosters. Overall, this lean stumble is fairly minor. And is only noticeable if I'm pulling away from a stop like a granny. All other throttle inputs are very nice, crisp and linear. A whomp to the floor from a stop results in tire smoke. So, I'm not dissatisfied. Just wish I could eliminate it altogether.
       
    • 68 Coronet RT

      68 Coronet RT 68 GTS # 508 in Registry

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      7milesout
      If you are having these issues with the 1405 carb why keep messing with it if you have a brand new AVS-2 sitting on your shelf ? Make the change and you won't regret it unless you like driving yourself crazy
       
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      • Go Mango

        Go Mango I drive it like I stole it

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        My original Carter AVS
        If I'm reading this right, you have an AVS2 and your still adjusting the other carb. I'm thinking I would try the new one. Maybe the annular discharge will help?
         
      • 7milesout

        7milesout Well-Known Member

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        You and GoMango are correct. I do have it on the shelf. But I'm friggin OCD. I get my mind made up about something, and I just can't change my mind. I guess that's OCD, or stubborn … or stupid. Maybe a combo of all 3! :D

        I made up my mind that this Scamp is going to run a 13.99 E.T. on it's current set-up (with lots of tuning) before I bother putting the AVS-2 on there. I have 2 hurdles in hitting the 13.99 second target at the moment.

        1. El Scampo is vapor locking. I have put thermoshield tape on the fuel lines near the headers. It helped a little. I raised the float height from the Edelbrock spec (7/16ths?) to 5/16ths. That's the gap of the float to the rubber gasket on the upper housing (in the manual). I haven't had a chance to try that yet because...
        2. The ammeter pegs out from time to time.

        Guys - I know you guys are busy as beavers too. But I still have a full time job, 3 sons, 2 parents with cancer, and a wife that as mean as a rattlesnake. I'm having a difficult time finding time for El Scampo. Plus I'm a bit miffed at El Scampo for all the vapor locking. The one time (last fall) I had a full pull all the way down the track, I accidently short shifted a bit into 2nd gear. And ran a 14.179. If I hadn't short shifted I might have hit my 13.99 goal. I'm resisting adding an electric pusher pump (near the tank / rear axle) to push cool fuel on past the hot spot(s). That's next though if the deeper puddle of fuel doesn't work.

        I've got to sort out the electrical problems (I have a couple ideas) before I drive it again, as I don't want to burn it up.


        7milesout
         
      • 68 Coronet RT

        68 Coronet RT 68 GTS # 508 in Registry

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        Back in the old days we use to run cool cans when we had that vapor lock issue. What are you running for fuel ? Non ethanol ? or Ethanol. The reason I ask is some engines when they run hot will boil the ethanol enriched gas causing a vapor lock and hard hot starting. I run 91 Non-Ethanol and never had a vapor lock issue and last year my Dart always ran 210 to 220 everyday because of a cooling issue that I had. That's another story, I resolved that with a Direct fit Cold Case radiator. We had a couple of 75 degree days here and granted that's not hot outside by any means but she never got above 160 so my over heating issue is fixed so far.
         
      • 7milesout

        7milesout Well-Known Member

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        I'm able to find 90 octane non-ethanol in a few places around me, and that's what I always run. This vapor locking is so consistent, and the AFR gauge tattles, and makes things obvious. I don't know how anyone trying to blast down the quarter mile can live without an AFR gauge. Anywho…

        It was 6 to 7 seconds it would run out of fuel. Now it is more like 7 to 9 seconds (with the tape heat shield). But, on the line, the fuel in the bowl is fine. It leaves the line nice, full power, at least at partial throttle (because I have skinny 14" tires). AFR gauge shows perfect AFR. So it is not boiling in the carb. Once at full throttle the power is awesome. Until it falls on its face and the AFR gauge slams up to 20+, at which point I back out of it. It is heating the fuel line near the right header while I'm gently power braking it on the line. Then the mechanical fuel pump cavitates from boiling fuel and fails to replenish the fuel in the bowl. The bowls drain down consistently and when there's not enough fuel, it falls on it's face. On the street, it never vapor locks. An 1/8 of a mile track it would be fine.

        I'm hoping that raising the floats extends the time out to where it would run out of fuel. And that maybe the fuel pump could still spit enough fuel to keep it going to the end of the track … maybe airflow (moving down the track) would cool things off and the fuel pump would start becoming more effective. I doubt it's going to work, but I'm resisting the electric pump.


        7milesout
         
      • 68 Coronet RT

        68 Coronet RT 68 GTS # 508 in Registry

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        I'm hoping that raising the floats extends the time out to where it would run out of fuel.

        Are you sure it's vapor locking and not just running out of fuel ? What Intake, Cam ( Lift and Duration) and gears are you running ? Stock bore, what heads ?
         
      • 7milesout

        7milesout Well-Known Member

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        The only reason it would run out of fuel is for the vapor locking.
        • Intake: Stock (will procure and install an rpm air gap after AVS2).
        • Cam: Dunno mate. P.O. said it was something like a 280 / 280. Not super aggressive, but more so than stock. Whatever it is, the stock intake is the biggest air pinch point.
        • Gears: 3.23, I changed from an open diff to an Eaton TrueTrac. 8-3/4 (the good number) diff.
        • Bore: Stock
        • Heads: I'm assuming stock LA 360 heads.
        • Trans: 727
        • New fuel tank, new sender, and new fuel pump. Gas free flows down the line like Niagra Falls.
        • TTi headers, complete new exhaust.
         
      • 68 Coronet RT

        68 Coronet RT 68 GTS # 508 in Registry

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        The only reason it would run out of fuel is for the vapor locking.

        Not necessarily you could be under carbed but in your case I don't think that's the issue. If you have a temp gage what is the engine temp when you are running ?
         
      • 7milesout

        7milesout Well-Known Member

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        According to the gauge, it is cool as a cucumber (meaning, at the thermostat set point, not higher). I should mention, the radiator got a good cleaning at a radiator shop. Coolant is all fresh. I usually mix about 60% (distilled) water. As a tidge more water pulls off heat better. And, it really doesn't get very cold in the dirty south.
         
      • 68 Coronet RT

        68 Coronet RT 68 GTS # 508 in Registry

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        Something doesn't sound right, do you have a fuel pressure gage.
         
      • 7milesout

        7milesout Well-Known Member

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        Something's not right all right … it's vapor locking. No fuel gauge, but brand new fuel pump.
         
      • 68 Coronet RT

        68 Coronet RT 68 GTS # 508 in Registry

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        You might want to send Rusty Rat Rod a PM he's on post #3. He responded to the original post maybe he can help you out. Sooner or later you will put that AVS-2 on and you will say why was I even bothering with that other carb. Good luck my friend
         
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