Holley Sniper Quadrajet Conversion - 1972 Electra

Discussion in 'High Tech for Old Iron' started by Electra Bob, May 8, 2019.

  1. Electra Bob

    Electra Bob Well-Known Member

    Still have a few odd jobs to complete but the main work is all done and the Electra is back on the road and safe to use according to the State of Massachusetts!

    I tend to get rather wordy when writing things up so to spare you all that I put together a more pictorial record of the project that you can find here: Holley Sniper Project

    Feel free to shoot me questions and comments both here and privately.

    Overall this was a fairly involved but pretty simple project complicated slightly by having to use a non standard fuel tank. I replaced everything from the filler cap to the manifold to have a nice clean and safe fuel system end to end.

    By far the most time consuming part was removing all of the old plumbing while lying on a cold concrete floor under a car supported by ramps at all four corners.

    Once everything was installed and final checks complete it was time to fire it up. I turned the key expecting to hear the fuel pump start so I would be able to set the fuel pressure and check for leaks... nothing! I shut down and started doing electrical tests on all fuses, relays and connections. Everything checked out. Huh?

    Turned the key again and this time waited for the Sniper screen to finish booting and went through the initial configuration. You get to set number of cylinders, capacity, target idle speed etc.. Once that was done and the system powered off and restarted the sniper decided to send power to the fuel pump. What a relief! I wrote Holley support and suggested they add a note to that effect in the manual.

    With the fuel pump running I could set the fuel pressure to 60 psi. Checked for leaks and found none. Pressure testing fuel lines is an absolute must do! I had to redo one hose end due to a leak.

    With fingers crossed I gave the key a further turn and... fired right up after being idle for a little over a month. A few seconds of roughness and then settled down to a smooth idle. Score!

    Longest trip so far has been to work and back, about 15 miles each way, so still lots of self learning to do for it to create a fuel map for the car. Overall I've noticed a bit more pep, smoother running from start up to idle and cruising and no more fiddling to set the choke and attendant fuel smell.

    Not expecting a huge improvement in gas mileage but 1 MPG more would be a ten percent improvement :)

    Houmark and Rockable like this.
  2. B-rock

    B-rock Well-Known Member

    great news! ill be doing the same on my 65/455. Glad to see a holly write up.
  3. garyd

    garyd Well-Known Member

    im doing this on a 75 park avenue
    did you replace metal lines because of rot?
    what improvements did you notice?
    where did you get your fuel pump blocking plate?
    im using the in tank holley pump as well.
    ill have more questions as i dig into it
  4. Electra Bob

    Electra Bob Well-Known Member

  5. Electra Bob

    Electra Bob Well-Known Member

    Several reasons for replacing the fuel lines not least of which was because of corrosion. The system needs to handle 60 psi and having to use an inline filter pre throttle body and a regulator post throttle body meant none of the existing under hood plumbing would be practical.

  6. Taulbee2277

    Taulbee2277 Silver Level contributor


    Great write up! I am anxiously following your thread and results. If I ever made one definitive 20th century upgrade to the GS it would be the same setup.
  7. Rockable

    Rockable Active Member

    Great job, Bob! I will use this when I do my 49 Buick with 455.
  8. Electra Bob

    Electra Bob Well-Known Member

    Quick update after having lived with the Sniper for a few weeks though the weather has been so bad I have not been out and about much.

    One thing I have finally learned is to keep my damn foot off the gas pedal when starting! I don't do the choke set pump any more but noticed I have a tendency to add some throttle when I hear it fire and this seems to cause it to flood.

    If I keep my foot off the pedal and let it do it's own thing it cranks and fires up OK and after a few seconds it settles into a good idle.

  9. Ken Warner

    Ken Warner Stand-up Philosopher

    Have to believe that like the FAST and Fitech systems I've used, if you turn the key to ON and give the O2 sensor a few seconds to warm up before cranking, most cold starts will be painless.
    sailbrd likes this.
  10. Electra Bob

    Electra Bob Well-Known Member

    Almost a month since my last update and the weather is definitely more conducive to cruising :)

    So the Sniper is a self tuning EFI system which means you can pretty much bolt it on, set up a few basic parameters which will configure a default base map and then let it do its thing and it'll run just fine.

    As you drive the car it uses feedback from the sensors to adjust fuel delivery in order to attain the target air fuel ratio. It averages these adjustments for given conditions and writes them into a learn table which it then uses in conjunction with the base table to provide future fuel delivery values.

    One of the monitor screen shows the Current Learn % which is an indication of how much fuel it is adding or subtracting from the base map. Although it is normal to see values +/- 20% it does mean it is having to constantly make those adjustments. The Electra would often show values around and sometimes a little over 20%.

    Well after having put a good few miles on in varying driving conditions the learn table should have pretty much narrowed down the adjustments required and guess what? Yup - we can write these into the base table so it reflects the needs of the vehicle and how it is driven.

    Today was going to be a nice sunny day so I decided to drive the Electra to work. Before starting up I used the Sniper controller menu to update the base table with values in the learn table. On the ~15 mile drive to work on nice quiet back roads I never saw the Current Learn % value go over 2 %.

    Though purely a subjective assessment I did feel like the car ran even smoother. Still two thumbs up for the Sniper Quadrajet!

    ravensbud likes this.
  11. BennyK81

    BennyK81 Well-Known Member

    Do you hear the fuel pump when you turn the ignition on?
  12. Electra Bob

    Electra Bob Well-Known Member

    Yes - I hear the pump get up to pressure at key on but once the engine is running I don't hear it. In the Electra it is of course it is in a different time zone...

    With the aid of another pair if eyes and ears under the hood I did discover there is a fairly constant pulsing in the fuel lines that can be heard at idle. Been meaning to ask Holley if this is normal. Again, don't hear it under normal driving conditions.

  13. Steve73GS

    Steve73GS 73 GEE YES

    Hello Bob or anyone else running Holley Super Sniper,
    What did you do for Air filter and base/top? Keep stock or something different? K & N, Holley, etc?

  14. Electra Bob

    Electra Bob Well-Known Member

    Steve73GS likes this.
  15. Steve73GS

    Steve73GS 73 GEE YES

    Looks good Bob. I was also going to go with drop base because of height concerns, am hoping 4 inch filter will fit, we'll see. Thanks.
  16. Electra Bob

    Electra Bob Well-Known Member

    Using a straight edge across the cross braces shows the 3" filter has just enough clearance from the hood. Unless you have more hood clearance I don't think you'd get away with a 4"

    Steve73GS likes this.
  17. Electra Bob

    Electra Bob Well-Known Member

    Grabbed the closest thing to a straight edge and snapped a pic this morning. This is the 3" drop base filter on the Sniper Quadrajet on a stock manifold.

    Steve73GS likes this.
  18. Steve73GS

    Steve73GS 73 GEE YES

    Thanks for the pic Bob. Hmmm, looks pretty close on yours. Hard to tell exactly with my pic ( I don't have car...it is being worked on), thought I might have room but now I have doubts. There was no issue with the base fitting over the EFI? I suppose it's standard but wanted to confirm before ordering. I called Holley and K & N (prefer K & N filter) but neither could tell me definitely. Holley makes a kit with drop base, filter and lid which I'm sure would fit since it's designed for EFI but the K & N provides much less restriction, just not sure about fitment on the K & N.
  19. Electra Bob

    Electra Bob Well-Known Member

    No issues with the base fitting the Sniper.

    As far as air flow -keep in mind the stock filter horn inlet is only about 2 inches in diameter so any of these provide way more.

  20. Steve73GS

    Steve73GS 73 GEE YES

    Good point. So really, the only thing to consider at this point is whether to go with something unmarked and generic looking (Summit, K & N, etc) or the Holley with the fancy "Sniper" marked on it? Have a fair amount of bling and manufacturer's names on engine already so will go with generic look to tone things down some.

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