I’ve Gone Full-Sniper on my ‘72 ‘Lark Ragtop

Discussion in 'High Tech for Old Iron' started by SkylarkRagtop, Jan 16, 2023.

  1. SkylarkRagtop

    SkylarkRagtop A life beyond full

    I’ve had this 72 Skylark since ‘94. Because I liked the Quadrajet I bought the Holley Sniper Quadrajet (that roar is real and I always liked it), a new Tanks Inc EFI tank with pump and sender, and a regulator on the firewall (the QJet versions of the Sniper do not have an internal regulator). In addition to reduce the pulsations in the line I put a Radium Engineering fuel pulse damper on both the feed and return lines of the throttle body. I tried one on the return first, made the feed pulse more, and vice versa with just one on the feed. Two of them cuts the pulsing by maybe 90%.

    I also got the full hyperspark ignition system as well, timing controlled by the ECU. I’d gotten the EFI installed, checked that it was all good, and then put the ignition in after. The lighting storm from trying to run it on spark plug wires dated 1994 was amazing. I quickly shut her down before she fried herself and made up the MSD 8.5 set I’d bought. After that, the Wizard was run, and we went off for a test drive.

    Nice, but meh. I read this board and put in some start, idle, cruise, and WOT timing values I found to see what’d happen. Went out for another test drive and I ended up scaring myself silly. Holy crap was she fast! Bone stock 350, TH350, a 12-bolt non-posi rear that I’m told came out of a station wagon or something. Karen never ever did burnouts before. Not even with braking and revving. Now? Put your foot to the floor from a standstill and smokey burnout ensues leaving a strip of my new tire on the pavement.

    I couldn’t get the IAC where everyone says it’s supposed to be, until I backed out this tiny Allen head screw that sits up against the lever of the secondaries. I guess that was keeping the secondary butterflies open just enough to raise the idle to the point where the IAC was not needed so it was always at 0. The slotted IAC on the primary butterflies was all the way out, not even touching, and it wasn’t until I turned that Allen screw that I could follow the procedure and get the IAC to 2 at idle. For some reason, the car runs worse that way, even after starting the wizard and re-learning again. All I’d done was let the secondaries close all the way. Or maybe on the Q-Jet version they’re not meant to? All 4 butterflies on the regular sniper move in unison and there are progressive linkages to tame that for drivability, but Q-Jet version comes with that setup. What’s the point of that screw anyway?

    So I’m getting a little frustrated because that first test drive had no bog, no flat spots, nothing but smooth power anywhere you wanted it and awesome drivability… but 0 IAC and an idle that didn’t want to go below 750 or so. then I touch that screw and screw it all up.

    Does anyone here have a configuration file that’s been working for their stock 350/4bbl that I can take a look at to get a sense of what kind of tuning I’m supposed to do? I used to tune my car by ear, nose, vacuum gauge and timing light. I think it’d help if I could visualize what’s known and supposed to work for this engine.

    Thanks for reading this novel-length post and I look forward to participating more. There was barely an internet back when I got this car. My Year One catalog was on paper!

    Here’s some pics. Please forgive the horrible bodywork from 1994 when a friend and I did body and paint in my home garage (because I had no money). Then there’s was a pic of where the handheld lives, and the location of the Allen screw I was talking about.

    Attached Files:

    Last edited: Jan 16, 2023
    patwhac, Dano and Max Damage like this.
  2. Bens99gtp

    Bens99gtp Well-Known Member

    I'm not familiar with these units......but is the adjustment on the secondary the only or is there an adjustment up front.

    Now this also tells me there can be a vacuum leak somewhere else too.

    If it was me I'd put the secondary back to where it was to get my better drivability back and look for a vacuum leak and if not live with it at 750 idle........ultimately you have to live with what makes your motor happy not living making the piece of paper happy.

    I opened the secondaries on a holley b4 to let more air in so I could close the front to delay the mid signal booster pull. The main circuit was coming too soon.....I delayed that successfully, but I never could get a good balance of idle.

    Often times a compromise has to happen, and you might have to choose the least problematic issue to live with
  3. SkylarkRagtop

    SkylarkRagtop A life beyond full

    There’s a slotted screw that can be used to raise and lower the idle by pushing on the primary throttle lever. The secondaries are linked to come in about midway through the throttle travel, or however a Quadrajet carb works. The Allen screw I referred to seems like a “stop” screw on the secondaries the way it’s set up, so once opened by the throttle, it springs back against that screw that was limiting if those plates could close all the way. That’s why my idle stayed high and the IAC didn’t have to chip in any air.

    I’ll see if any tuning changes make the engine feel like it did before I backed that screw out and went by the book, and if not, I’ll crack the secondaries a little at a time till it feels the way it did.

    I just had a thought: When you blip the throttle - way before the secondaries even budge - the injectors fire in all the bores. Where’s that fuel in the secondaries going to go if the butterflies are closed all the way until you’ve pushed the throttle open enough to open the secondaries too? Maybe that’s why it bogs… a dump of the collected fuel? Hmm. I’ll have to investigate.

    I think I might know where there is a little vacuum leak. I’ll have to see. She runs smooth at idle and sits there around 19-21 or so on the gauge. I think my PCV grommet is old. I put a breather on the valve cover where that hose was that went to the air cleaner. Otherwise I think she’s pretty tight, vacuum-wise.. spraying carb cleaner at the lines and ports doesn’t change idle at all.
  4. 72gs4spd

    72gs4spd Well-Known Member

    I have a square bore sniper but I’m very sure there’s a parameter for when the fuel injectors turn on for the secondary’s. It’s regulated by the tps.
  5. BillA

    BillA Well-Known Member

    I have a Holley Terminator set up and when I set the idle speed mechanically I bypassed the IAC by putting a piece of duct tape over the IAC air inlet. That is recommended by Holley. Did you so the same when you adjusted the idle screw?
    Last edited: Jan 24, 2023
    sean Buick 76 and Max Damage like this.
  6. SkylarkRagtop

    SkylarkRagtop A life beyond full

    Yes. I tried it the way Holley suggested in the instructions and the way EFI SystemPros suggested. Until I backed off the Allen screw that was up against the secondaries lever, nothing I tried got the IAC off 0. Once I closed the secondaries the methods worked. But oddly enough with the IAC set and that Allen screw backed off the car performed worse. I’m going to tinker with it and screw the Allen screw back in a little at a time and adjust the slotted screw as needed to try and get it running the way it was.

    I also got the USB dongle so I want to use my new $130 laptop (amazing how cheap these things can be now) to tune the maps for fuel and spark.

    I was hoping someone here had a configuration they’re happy with and could share the file so I can see where to start tweaking things.
  7. sean Buick 76

    sean Buick 76 Buick Nut

    Time for a Q jet upgrade
    Tomahawk likes this.
  8. SkylarkRagtop

    SkylarkRagtop A life beyond full

    That’d be old tech for old iron, but yeah… the Qjet I’d rebuilt in the 90s was pretty darn good. The lure of new tech is powerful. And while I don’t yet have it optimized the Sniper has been impressive. I need to learn more about tuning it.
    72gs4spd likes this.
  9. Phil

    Phil It really *is* a 350...

    I’ve been slowly squirreling away parts over the last year or so. I also bought the Sniper Qjet, the hyperspark distributor, coil and CD ignition. I’m going to drop and use the original gas tank. I’d be interested in seeing your tune and comparing the results.
  10. SkylarkRagtop

    SkylarkRagtop A life beyond full

    That’s good, Phil. I think you’re going to like it. Make sure you get the new thick plug wires and new plugs. It’s amazing how much juice that ignition puts out.

    Also, I’d be interested in knowing what the screw on your secondaries is set at. PM me if you need more info on what to look for. Out of the box, it made getting the idle dialed in a challenge until I backed that screw out.

    The tank on my car had a couple of blobs of putty on it from pinholes, and I didn’t even care to look inside it, so I got an EFI-ready tank. Not sure how other options would have worked out, but so far I’ve found the pump supplied with the kit to be noisy. First on screamed like a banshee, second one has an audible whir, but I’m currently working on a new 2.5” exhaust system install, using two Dynomax 20” Super Turbo 17749s. That’s a whole other thing. TA performance told me several times to get an offset in/center out muffler but that was not what I needed. Offset/Offset ones are in the box waiting for it to not be 20 degrees out.

    During the install I’m going to relocate the o2 sensor further upstream now that the pipe will be out and it’s not a bent up mess like what was in there. I have a feeling the car will run better with a more accurate read of my AFR.

    As for tuning, I’m learning little by little how to tweak things. After I get the exhaust done and some other stuff addressed I’m going to devote more time into tuning it.

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