Another Sniper build tread

Discussion in 'High Tech for Old Iron' started by Trond-Jarle Pedersen, Jan 13, 2021.

  1. Morning,

    I though that since we have no threads on Sniper EFI install I would make yet another.

    I will convert my 72, Skylark Custom that is as close to stock as could be with its 350 4-barrel, single exhaust.
    90% original paint but new rag-top.
    Only prior visible non-OEM modification to this is lowering springs and the removal of the Air pump
    (it locked up and is not mandatory in NYW, still have all parts needed to add a new back on)


    I Bought the car in Central Valley California in 2011. it is a well maintained original that now have 76k miles on the clock
    It came with original purchase documentation and I am second (third if you count the daughter of the original owner)

    With the exception of normal maintenance I have not done a lot to this car since it is is so solid and just plain works.

    Normal maintenance have included:
    New shocks and springs all-around
    New ball joints and all bushings
    New valve seals
    Oil/Coolant etc. all around a few times :)

    However, since I have run out of winter projects and I scored a Sniper locally I figured it was about time to upgrade it a bit.

    My goal is to visually keep the engine bay visually as stock locking and hide as much of the EFI as I can.
    I also pledge to not do any modification that can not be reverted, and I will keep all parts pulled off it so it can be put back to the original condition.

    I am only working on the car in the weekends and this project will probably take a couple of months with weekly updates.

    To keep this thread not to "image heavy" you can see additional images here:

    So, with that said here we go:

    I will go the full length on this project using mostly the Holley Sniper product line.
    As said I got a Sniper locally which of course lead to several additional purchases...
    New fuel system with Holley's in-tank OEM style pump
    Complete HyperSpark ignition system

    Before Christmas I did some checks on the engine to ensure it was healthy.


    I measured timing chain stretch by turning the engine clockwise, marked the balancer at zero degrees and rotated the crank CCW until the rotor moved, 12 degrees is excessive so new timing chain here we come...

    While i was at it I also pulled the stock intake manifold, removed EGR, bead blasted it and painted it semi-gloss silver
    (Could not find engine paint that was close to the correct color locally)


    A quick test fit of the Sniper on top of the manifold shows that I need a spacer and not just the seal-plate that Holley suggest.
    The alternative is of course to cut of the transmission part of the throttle leveler, but I prefer not to do so due to warranty reasons.

    Parts laid ready for assembly:

    Build plan/coming in the next weeks :
    1: fuel system including pump and lines
    2: wiring
    3: first start
    4: Ignition system replacement
    5: cleanup and final work
    Last edited: Jan 13, 2021
    docgsx and buicksWILD like this.
  2. 72gs4spd

    72gs4spd Well-Known Member

    I did mine last year you will definitely see a difference if I did on my 120K+ motor. I did have a Quadrajet Power rebuild on it and was very pleased. My only advice is to go with an in tank pump. I used Tanks Inc. They use Walbro pumps or at least the 340lpr is. Good luck.
    Trond-Jarle Pedersen likes this.
  3. I have had cars with aftermarket EFI and external pumps before and will definitely be using an internal pump on this.
    I have a Holley OE style EFI fuel tank module ready to install, the main advantage I see with that module is the fact that I do not need to run an return line (in addition to the noise reduction)
    Although not best from a performance point of view it is more than sufficient for this engine.
    Last edited: Jan 13, 2021
    gobuick likes this.
  4. Electra Bob

    Electra Bob Well-Known Member

    Curious - did you go with the Sniper square bore or Sniper Quadrajet body?

    Sniper Quadrajet plus Hyperspark has worked well for me.

    Definitely do the EFi install with the stock ignition first then add the Hyperspark after.


  5. It was an impulse buy when I saw a local ad for a new one for a very low price so it is a shiny squarebore
    If I where to buy directly from a dealer I would have gone with a goldchromated spread bore.

    Then I went and spendt 2x on fuel and ignition system..

    Might as well...
  6. Electra Bob

    Electra Bob Well-Known Member

    You'll be glad you made all the upgrades.

    The Electra ran better with the Sniper and better still with the addition of the Hyperspark ignition.

    docgsx likes this.
  7. Redmanf1

    Redmanf1 Gold Level Contributor

    docgsx likes this.

  8. That is the one I will be using,
    Starting on that and the rest of the fuel system tomorrow
    Expect an update on it and how it is to mount on Monday.


    Trond Jarle
  9. Good progress this weekend.

    Started with emptying and pulling the tank

    And scored a build sheet (?) that was stashed on top of the tank,
    But not sure if I would call this a build sheet, it differs quite from what I have found in other GM products.

    Pulled the original tank module and compared it to the new Holley OEM style in-tank module, looks good
    One note: the outermost pipe portion of the new tank is not 3/8, it is only 5/16, it then tapers up to something that is a bit less than 3/8 before it goes down in the tank.

    The pump module came with new O-ring and lock ring so a complete solution
    The only thing I was not to impressed with is the size of the output pipe, even the large portion of the pipe is slightly smaller than a normal 3/8 hard line and the clamps was a bit loose.
    Fixed this with an adjustable fuel-injection hose clamp (not shown) in addition to the press on clamps

    Tank up and connected to the original hard line
    (the pump wiring is not connected and just hanging down)

    I mounted the fuel filter where the original hard line was split
    As I was under the car I also sprayed the underside with a transparent wax coating since the underside was original and untreated.

    From the frame to the car it was another small portion of hose, before meeting up with a new hard line going to the top of the engine.
    Added some length to the hose to allow for the engines movement.
    I used a pipe beader to make beads on the new pipe so no AN couplings on this end.

    I wrapped the new hard line in wire-braiding to protect it a bit and added a pressure gauge.
    Flushed and pressure tested the system.
    The pump is surprisingly quiet compared to the systems I have used before

    Overall impressions of the Holley OEM style in-tank pump:
    Nice kit that is easy to assemble and fits in the tank without modifications
    Very quiet pump
    But the output pipe should be a larger diameter, no point of having a 5/16 pipe at the end since the Sniper requires 3/8.
    Also the pipe should be 3/8 and not undersized.

    Some more pictures can be found here:

    Next weekend: pull and connect all wiring to the EFI
  10. Redmanf1

    Redmanf1 Gold Level Contributor

    Great info... What if you cut the small end off to that second bevel??? Looks like it would seal fine, kind of like a stock line end..
  11. That is what I did, cut it and added a new bead to the end.
    No pics of that but this is how the bead looks.
    If I did not have the beading tool I would probably cut the end so that I kept the original bead/bevel.
  12. Redmanf1

    Redmanf1 Gold Level Contributor

    Thanks for the info..
    Trond-Jarle Pedersen likes this.
  13. Redmanf1

    Redmanf1 Gold Level Contributor

    I am looking at the holley terminator X Max stealth 550-1014 and the holley OEM style fuel tank module 12-303 for my 496.
  14. Ooo,
    That Terminator is sweet.
    But would a returnless system as the 12-303 be suitable for the Terminator?
    I think the returnless might be a bit limiting if you are going to run nitrous and definitively not suitable for boosted applications.

    (the in-tank regulator can of course be blocked and a return added to the tank if you want to modify it)

    If I was living in hotter climate I am not sure I would be running with a returnless system due to the risk for vapor-lock.
  15. Redmanf1

    Redmanf1 Gold Level Contributor

    I will not be using a power adder so it should be fine. I called and talked to a Holley tech.. He suggested this model would be less sensitive to RF noise.
  16. The pump is a 255lph so then it should be fine.
    And the lack of pump noise is also very nice,
    but I assume that with a 496 you also have a free flowing exhaust so that might not be that important for you...
  17. Redmanf1

    Redmanf1 Gold Level Contributor

    I am running stainless works headers with a full stainless MagnaFlow exhaust. It's not that loud. This is more of a cruise car and it's a convertible with AC and loaded with options. No RaceTrac for this girl
  18. Are you going for the Hyperspark timing or a different solution?

    AC, that reminds me:
    To wire up AC to the Sniper or not...
    It is not like it is really needed but...
    Oh well, guess I'll figure that out next week.
  19. Electra Bob

    Electra Bob Well-Known Member

    Three thumbs up for Hyperspark. It's darn close to plug-and-play and once it's set up the Sniper takes care of ignition timing from there on.


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