Holley Sniper W.O.T issue

Discussion in 'High Tech for Old Iron' started by RobertRobitaile, Jul 21, 2017.

  1. RobertRobitaile

    RobertRobitaile Well-Known Member

    Any One using Holley's sniper EFI? I have been fighting with it since May and not getting good results. My 455 has 25cc forged pistons I'm running stock 73 heads, a TA 290-94H cam and a edelbrock performer Buick 455 intake. Holley's tech guys have been trying to help as well but we are not making much progress. I am also running a MSD Distributor and have the Holley system running timing control. It starts, idles and cruses ok but it is awful at W.O.T. It wont even squawk the tires off the line and can barley pull past 4000 rpm. Any experience is appreciated. I have a 1" open spacer on it. The fuel pump it supplying 68 psi even at W.O.T under load. We had the same trouble before timing control was installed with the factory points distributor. Holley asked me to connect the timing control in order to make sure it wasn't an ignition problem. The fuel tank is like new inside and out only about 5-6 years old. I installed a Holley in tank retrofit pump and sending unit. The sniper wiring harness it supplying the power source directly to it. There are not any O2 leaks that I can find. The plugs look quite lean. Holley said an exhaust leak typically causes a rich condition. I have new Taylor wires new MSD Distributor and coil. Holley says their engineers are working on it but have not given me anything to test in 2 weeks now. I have a sent a bunch of data logs and also the global configuration file. The tech guy said he can clearly see the symptoms in the data log but can not understand why its doing it. I din't try to cheap out I got all the parts Holley recommended to work together. Just cant get good results yet
  2. Ken Warner

    Ken Warner Stand-up Philosopher

    So I'm assuming it ran fine with a carburetor? Have you checked to see if you are getting fuel in all 4 bores of the throttle body?. Double check the fuel filter(s)? Make sure you have things sufficiently grounded and redundant ground straps? MAY sound crazy but the same issues that cause stereo noise will anger the EFI. The FAST systems would stumble and grumble with pretty much anything but a tach output from an ignition box. I try to read a bit of what is going on with the Snipers from their Facebook page but most of the problems that pop up are the same across the board for all EFI conversions. Occasionally you get someone that actually has a bum unit, maybe you are one of them?
  3. RobertRobitaile

    RobertRobitaile Well-Known Member

    I have not checked to see if all 4 injectors are working but will do. Yes the car was running great before I put the efi on. Makes me wish I had left it alone. Most of the problems I have been able to find that other people are having are idle issues. Mine works fine at light throttle and idle. When traveling down the road at more then 1/2 throttle is has no go at all. if i slowly let off the car starts to pull harder. Its very strange
  4. Ken Warner

    Ken Warner Stand-up Philosopher

    As suggested in the other thread this could be a primary ignition problem but the fact that it ran fine before the EFI sure makes it look like there is something in the system causing your problem... FWIW once you get things ironed out with the EFI you will be happy to have it on there. Easy cold and hot starts, better throttle response from idle to at least deep into part throttle. If the carb was setup close you probably won't notice much difference at WOT. Controlling the AF ratio at low speeds will also help keep you from wreaking of hydrocarbons every time you go for a spin too! :)
  5. RobertRobitaile

    RobertRobitaile Well-Known Member

    That's one of the main reasons I put it on was to get rid of the odor my wife and daughter always complained about. I was even contemplating putting on a couple hi flow cats. Also I wanted to try and tune it for a bit better fuel mileage at cruse.
  6. brands5.0

    brands5.0 Active Member

    Did you figure out the problem?

    If not I was watching the show with the roadkill guys testing efi vs carb. and they used the Holley sniper and had issues with it on a dual plane intake. Swapped to a single plane and it ran fine.
    Julian likes this.
  7. Sabertooth

    Sabertooth New Member

    I'm having all kinds of problems with my sniper 2months the cars been down and nothing but extremely slow replies from tech support.
    My question is what are you running for WOT & cruise timing?
  8. Ken Warner

    Ken Warner Stand-up Philosopher

    Ballpark numbers are:
    14.1:1 idle too lean and you will get a lean surge
    13.8:1 part throttle
    14.0:1 cruise, too lean, see above...
    12.8:1 WOT

    Those numbers are by no means exact but they will get you in the ballpark. I think the defaults on the FiTech were in the same ranges and I'm betting the defaults in the Sniper are similar. The Facebook page(s) for the Sniper will have a lot of good info as will the Fitech pages. Both systems tend to have the same install problems which is probably what you are fighting with.

    And now I see you are asking about timing not fuel ratios...

    My bad.

    If you think.it's a timing function issue have you tried unlocking the distributor and using the weights and springs? At least for trouble shooting purposes... Otherwise about 40deg at cruise and 32 at WOT are good ballpark values. (more on cruise as compression will allow). If you are going to use the Fitch for timing you may want to look into phasing the rotor as well.
    Last edited: Sep 18, 2018
  9. gs_jimmy

    gs_jimmy Well-Known Member

    Run a compression check as well. Had similar issues with my system. Turned out to be a bad head gasket. Mine is going back together now and hope to be driving yet this fall. Let us know the issue when found
  10. NOTNSS

    NOTNSS Gold Level Contributor


    I'm late to this party (been in Montana all summer and not driven the car). I'm running the Sniper as well on my 455 but haven't had a chance to drive it for 'tuning' (installed in June) but if I recall correctly there is no provision for timing control on the Buicks... unless you did the lockout on the MSD. I got my Sniper here: https://www.efisystempro.com/sniper. Chris is very good at support and even if you didn't get it from him he has excellent articles on the website. Like someone above recommended, maybe get rid of the dist. lockout and run with springs and weight. EFI Systems recommends against the timing control on the MSD (or you can correct me).
    Again, mine is still infant so I can't report results either way yet. I'm trying to get a stable timing setup, seems to be jumpy so went to heavier springs in the MSD. Will keep playing with it.

    Good luck and keep us posted please.
  11. NOTNSS

    NOTNSS Gold Level Contributor

  12. KenC

    KenC New Member

    Hi guys, try this out: Replace the PCV valve with a fixed orface style, had a similar issue, the snyper will try to adjust the AFR mixture to mach the air coming in, if the PCV is letting in too much air you'll be over fueling, if you punch it and smell gas its either a vacuum leak or a PCV issue (Same thing)

    In my case I went with a fixed orface no ball or spring just a steady flow orface and my fuel usage dropped quite a bit, car got lots quieter, and lots more power and zero fuel smell.
  13. KenC

    KenC New Member

    Thank you, I tried to make this point on another board and got put down for it, I did that and and confirm it helps a lot, the other option is to use a spacer or have an air-gap manifold, having the intake split at the TBI just does not run smooth. so I second this.
  14. 72gs4spd

    72gs4spd Well-Known Member

    As for the PCV valve I used this one from Wagner on my 72 GS 350. Expensive but was much better than those one size fits all. AutoZone PCV valve that would vibrate at idle.

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