Page 1 of 3 123 LastLast
Results 1 to 10 of 25

Thread: Fuel Starvation Issues

  1. #1

    Default Fuel Starvation Issues

    I have a 383 SBC with a 550-512 Sniper sitting on top of a 177 Roots blower and it's using E85 for fuel. Last year Steve Morris made a great tune and it dynoed out around 775 FWHP. This engine is in a mud truck and I'm in the throttle for upwards of a full minute at times.
    I ended up melting the ring lands off the top of five pistons do to what looked like lean conditions. As luck would have it, I also found that the HyperSpark rotor had snapped its locating tab
    and that's what stopped the engine. Upon tear down, I had found the damage to the pistons. to my surprise, the cylinder walls have no damage. I think the rotor had snapped first before the pistons had anymore time to decide they did not want to be a part of the team.

    I installed my backup engine into the truck and put the blower and Sniper on it. This engine only makes about 550 HP. After about an hour, I had another rotor snap the locating tab off? I installed another rotor an all has been well on that issue. BUT, the engine started acting like it was starving for fuel when under boost (10 psi). It'd darn near die, and I'd have to select neutral and feather the throttle to let it catch up.

    My conclusion is that the A-1000 fuel pump is not large enough, or it's failing. I'm looking at the Holley 12-1800 to replace it.
    I use a 100 micro pre-filter and a 6 micro up front. The supply lines are aluminum -10AN up to the Sniper. My return line is an -8AN.

    Also, I'm not sure if I may have messed up with the regulator. I have it set at 60 psi. and I'm adding fuel per pound of boost through the EFI program on my laptop. Is this the correct way to add fuel with the Super Sniper, or am I suppose to set my Holley external regulator which is on the return side, at 70 psi? I'll be rebuilding the 383 SBC over the winter, and do not want to have a lean condition next year.

  2. #2
    Join Date
    Dec 2009


    Leave the fuel system at 60 psi, and tune the Base Fuel & Timing Tables. (Related Forum Post)

  3. #3


    @Danny Cabral: Thank you sir. That's what I did. Thought maybe I did it wrong.

    I cannot find an accurate answer if the Holley 12-1800 pump will be enough to supply the 775 HP supercharged engine on E85.
    I had found that the Aeromotive A-1000 was only good for 700 HP on a blown EFI feed engine. I feel this was the main reason for running lean.

  4. #4


    Quote Originally Posted by unforgiven View Post
    I cannot find an accurate answer if the Holley 12-1800 pump will be enough to supply the 775 HP supercharged engine on E85.
    I had found that the Aeromotive A-1000 was only good for 700 HP on a blown EFI feed engine. I feel this was the main reason for running lean.
    You should have the answers in your tune file and datalogs. The datalogs will show you how much fuel the engine is using at WOT. Your engine is probably using around 500 lbs/hour of fuel at WOT. If so, then you need a fuel pump that can supply more than 500 lbs/hr at 60 psi. You might need to convert to GPH or LPH depending on how the manufacture rates the pump. The Holley 12-1800 shouldn't have any trouble feeding your engine.

    You have the Super Sniper 4500 which means that you have the three additional data input lines. Sounds like you need to hook up a Holley fuel pressure sensor to your Sniper so you can datalog the fuel pressure. The Holley sensor is kind of expensive, but it's much cheaper than an engine rebuild. Once you hook the fuel pressure sensor up to your Sniper you can set an alarm so if the fuel pressure drops the engine shuts off. You can do the same thing with oil pressure.

  5. #5


    Hello Andy. I have the 550-512 Super Sniper 4150, not the 4500
    Yes, I have a datalog for the smaller 350cc engine.
    It shows 570 lbs/hr at 7.4 lbs boost at 5900 RPM.
    I do not have a datalog from the bigger 383cc engine. I just have Steve's dyno sheet.
    I do see where Holley states that the 12-1800 flows 140 GPH @ 60 psi.
    So if my math is correct, it looks to be enough for my engine with some extra for safety.
    140GPH x 6.6 ( weight of E85)= 924 lbs/hr.
    924 lbs/hr / .9 (BSFC of E85)= 1,024.6 HP.
    This looks like it will work for me with room to grow.

  6. #6
    Join Date
    Nov 2014
    Ont. Canada


    Sorry to hear about your meltdown. Datalog all your passes. Instead of guessing it went lean, you would've known if it went lean, if you had a datalog of the pass. It surprises me how many people ask for help and have not used the datalogging function. Datalogging oil & fuel pressure on a severe duty engine is always a good idea.

  7. #7
    Join Date
    Dec 2009


    Overlay the datalog onto your Config File, and pay special attention to the center paragraph in blue print:
    Originally Posted by Danny Cabral
    Quick Datalogger Information:
    Always provide data, not just symptoms. Is the AFR & ignition timing optimized? Overlay the datalog onto your Config File.
    Ensure the Target A/F Ratio table is properly programmed for your engine. Ensure the ECU is "Learning" (Learn Table LINK).
    Scroll through the datalog to the problem area. Then look exactly where this happens on the Base Fuel & Timing Tables. Scrutinize:
    RPM, MAP, MAT, TPS, CTS, IAC, Target AFR, AFR Left, CL Comp, Ignition Timing, Duty Cycle, Fuel Flow, Fuel Pressure & Battery.

    Using the Holley Sniper EFI software (LINK), look at where the live cursor moves to during this occurrence, and
    manually tune that area of the Base Fuel Table (enrich or lean) & Base Timing Table (optimize ignition timing).

    I find the most helpful datalog function, is overlaying the datalog on your Config File.
    I'm in the habit of using the datalog Overlay feature every time I review a datalog.
    Click on "Datalog" (on the top Toolbar), "Activate Overlay", then "Open Data Log".
    You can literally "playback" a recorded event, and watch it as it happened on any screen.
    Minimize (shrink) the datalog window, and move it to the bottom of any Config File screen.
    Then click & scroll anywhere on the datalog, and watch it playback on your Config File (EFI software). (Holley EFI Datalogger Instructions) (Datalog Information - Read "NOTES") (How To Record & Email A Datalog) (Closed Loop Datalog Tuning - Posts #2, #4 & #6) (Holley Sniper EFI Datalogging Tech Video)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  8. #8


    @81TransAm: Yeah it sucks. But it's part of the game we play. I was more worried about the $3000 block than I was about the pistons. I got darn lucky that nothing came apart, or did any damage other than the pistons.

    The truck is racing around in mud pits, it's not a 1/8th or 1/4 mile hit. It's under throttle for upwards of 15-20 minutes at a time ('s driven around under various loads), so heat is a major factor. The heat stays around 190°F for the most part. The AFRs are 7.1 under boost. (I can't thank Steve Morris enough for the great tune he made for the engine.) The whole setup is a learning curve for me. I'm slowly learning the Sniper EFI software and how to use it.
    Last edited by unforgiven; 10-30-2020 at 09:37 AM. Reason: Needed to clarify The under throttle comment

  9. #9


    @Danny: I do not really know how to make adjustments in a tune yet.
    I'm really green at what I'm looking at let alone where I need to make adjustments. But I'm not afraid to try.

  10. #10


    The Sniper will Learn, but if the Target A/F Ratio table isn't set appropriately, the damage can and will occur. I have learned the hard way there's power to be made at 12.8ish AFR at WOT, but not for long. For a supercharged engine I know it needs to be fatter than 12.5, but how much I don't know. I keep my WOT after around 12.3-12.5 to make sure the engine stays together this time. Good luck. You'll figure it out with research & practice.

Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us