Atomic EFI install

Discussion in 'High Tech for Old Iron' started by gs_jimmy, Feb 26, 2018.

  1. gs_jimmy

    gs_jimmy Well-Known Member

    Well I started on my update of the 1969 GS California over the weekend. Over the last couple of years the Holly 750 was running progressively richer, and the MPG was getting worse. So after building my LSx S10 I came to the realization that a more modern fuel delivery was needed.

    The car: 1969 GS California, with a 1971 GS455 Stage 1 motor and TH400 trans, rearend is a 3.31 geared Chevelle 12 bolt with Posi. Currently has a Holly 750 cfm 3310 Carb with manual choke.

    So I ordered up a new fuel tank and sender to replace the existing and original '69 unit. My issue here was that after I blew up the 4 speed, the car sat for a couple years un touched. since it had around 1/4 tank of fuel, rust set in. The fuel pump has been pumping dirt & debris ever since I started driving it again. Since an electric pump and EFI will have major issues with this stuff, a new tank is being installed.

    I did drop out the old tank on Sunday, and prepped for the new one to go in. I found that the old one has a dent in the center, and was starting to rust out on the lower drivers side section near the tank strap. After dropping the tank, I ran all of the old fuel out of the system. I then moved up front and pulled off the Holley Carb and manual choke.

    Once that was all done, I drained and replaced the old oil (very black and smelled of gas). Made a trip to the parts store to get new PCV, Plugs, air filter and MSD cap & rotor for the HEI. Tonight this all gets installed. Once I have it all up and running, I will reset the timing to 8*, currently at 6* and kinda doggy.

    Later today I will be ordering the EFI master kit (Atomic 2900 Master Kit) This appears to be the most complete system for the money. I will start by running this in a returnless configuration. A little harder on the pump, but since this is a pulse pump configuration, the "stock" Stage 1 @ 315 hp will be fine.

    My goal here is to clean up the fuel delivery that is running rich and delivering 8-12 mpg, to a system that will give me 15 mpg, clean tail pipe emissions, and a car that doesn't "stink" of unburned fuel & exhaust. More on that one later.

    Any thoughts on this set up?


    After this is all sorted out, I will be moving to an OD Trans for further MPG and performance gains (next year?)
  2. Harlockssx

    Harlockssx Brother Graw Mad

    If you're already delving into your fuel system, why not run it with a return line? It's already well established that they don't like it and the fuel control center is prone to failure when running returnless, why take the risk? Just a thought...
  3. Swagon

    Swagon Well-Known Member

    This system really needs a return, ive managed without but its optimal with. Also are you dead set on the atomic? Im actually getting rid of mine because its lack of tuneability doesnt agree with my cam and engine. also id sell it with a msd box for $800.
  4. gs_jimmy

    gs_jimmy Well-Known Member

    Ok, then here is a dumb question: Can I plumb in the 1999-2004 Corvette regulator and then add in the return line? My research is telling me that the system runs 30 to 60 PSI as a pulse system (returnless). The LS1 Vette is running at 58 PSI (constant) with an LS1 5.7. This is the same as the LM7 5.3 swap I just did.

    So it would seem that this is a cost effective way to add the return feature. I'd do this after I have the car up & running.

    Dalton, I literally ordered the system last nite and got the shipping notice already. I am not super concerned about total tenability, but rather a reliable system that I can install & forget. The Stage 1 really likes to drink gas with the Holley on it. I figured that the MSD system is going to really clean up the tune on fuel delivery. I also looked at Holley and FItech. Their master kit is not nearly as complete. We are not going for the last bit of performance, but rather a cruiser now. I have watched the episode of Roadkill with your wagon a couple times now, along with the MSD production video on the Malibu. This all seems to be the best bet for my goals.

    BTW - Did you ever get the manifold temp sender taken care of? Freiburger and Finnigan were really hammering on the fact that the radiator was not the best place for that sender. Mine has been replaced in the last few years, so I'm not expecting it to be frozen in place.


    GS California

    Drivelines so far:

    350 / 2 speed & 2.56 open
    350 / TH350 with a shift kit & 3.31 POSI 12 Bolt
    350 / Muncie M20
    455 Stage 1 with HEI/ Muncie M20 & 3.31 & headers & Holley 750
    455 Stage 1 with HEI / TH400 / 3.31 12 bolt (I blew up the 4 speed, all related 4 speed parts to Lakota in '09)
    Next up: the MSD swap and then a TH700R4

    I've owned this car since 1982 (First car), rebodied in 1997 due to severe rust (non-repairable frame & superstucture) about 60% of the current sheetmetal is the original car. Car was from MN & WI prior to me getting it.
    Swagon and 300sbb_overkill like this.
  5. Swagon

    Swagon Well-Known Member

    I wouldn't see why that regulator wouldn't work! thats a good idea really. For a real mild cruiser its the perfect setup IMO, but now I have a roller cam and the sp3 intake and it doesn't like it. and I did figure out the sender deal, it was a pain to get the fitting out of the intake but I got. Set up has changed since then though. rebuilt 350 with 10.5:1 comp, TA roller cam, roller rockers, sp3 intake, worked heads(waiting on aluminum's), and headers. doing a th400 swap blew up the th350 after 140mph luckily on decel lol.
    300sbb_overkill likes this.
  6. gs_jimmy

    gs_jimmy Well-Known Member

    Ouch, that hurts. What happened to the 400?
    Swagon likes this.
  7. Swagon

    Swagon Well-Known Member

    There was actually never a 400 in the car, previous owner thew that air cleaner on, they actually took a single inlet base and made their own ram air style base kinda cool actually. It had a tired remand 350 from a 72 dated car, and I rebuilt that.
  8. gs_jimmy

    gs_jimmy Well-Known Member

    Here is the spec on the cam: TA Performance rendition of the Stage 1 cam shows 210* intake and 224* exhaust @.050 with a 113* LSA. So the big roller cam is messing with the Atomic ECU parameters. It won't like cams over 250* . Anyway, since I'm still "stock" not really anticipating to much trouble. If the Roadkill guys can install in the parking lot.............
  9. Swagon

    Swagon Well-Known Member

    you should have no issues at all, timing control is kinda a pain to get working(feel free to message me when you get to that point if you choose to do that). my cam specs are 230/237 @.50 on a 110lsa.
  10. BillA

    BillA Well-Known Member

    Personally, I would have ordered a new tank with an electric in tank pump already installed. You can get those for $400-$700 depending on the brand. More expensive than a replacement tank for sure but you can save a few bucks on the EFI system by foregoing their inline pump. The in-tank setups provide for return and vent lines too. Do not skimp on the fuel system, especially with EFI. Build it now as if you're going to add power in the future. Ask me about my experience on the chassis dyno last Friday.:(
    Harlockssx likes this.
  11. ilikebmx999

    ilikebmx999 Well-Known Member has some cool efi tank/pump stuff.
    sriley531 likes this.
  12. gs_jimmy

    gs_jimmy Well-Known Member

    Guys, this is a limited budget. Looking at 1500 - 1600 total spend for everything.
    Atomic EFI $1250
    Fuel Tank $120
    Sender $20
    16" E. Fan $24
    Plugs $16
    MSD Cap/rtr $35
    PCV $2
    WIX Air Filter $8
    Oil & Filter $25
    New A/C foams $15
    TH400 filter kit $29

    TOTAL so far $1544.00

    Still looking to add in the ZQ8 or Jeep GC steering box along with the Poly bushings and end links ($200ish). Going to hunt down a known good TH700R4 and will get it rebuilt over next winter. That will also mean a console kit to update those dents & lens.
    300sbb_overkill likes this.
  13. gs_jimmy

    gs_jimmy Well-Known Member

    OK, last night, I replaced the plugs, cap & rotor and PCV. Plugs were really black and smelled very rich. So my suspicion about the carb is confirmed. I also had a cheap cap & rotor (aluminum terminals/thin plastic). Was at the end of the service life, so on went the MSD stuff. Heavier plastic, good brass terminals. Already have the good MSD plug wires on the car. My EFI is due in on Friday, so that means a good weekend of playing with the car. most likely won't get it done completely, but should be close.

    Still will need to fab the fuel pump mount to keep it lower than the fuel tank outlet. I think once I do have things up and running, I will get the Corvette regulator and go with a return line. One other thing I do need to do is drop the trans pan and fix a leak (annoying issue). This is a total junkyard find from 10-15 years ago. I've changed the oil & filter 2x now and everything seems to be clear and running fine. It did loosen up the shift shaft, so I'll fix that while I'm there too.
    Harlockssx likes this.
  14. Ken Warner

    Ken Warner Stand-up Philosopher

    Nothing mentioned about upgraded electrical system or installing an MSD. Most of these EFI systems will choke on anything less than a clean tech signal. If you are still running. 40ish amp external regulated alternater then be prepared to fight all manner of mystery problems due to electrical brown outs and bad grounds.
    ceas350, 1973gs and Harlockssx like this.
  15. TheSilverBuick

    TheSilverBuick In the Middle of No Where

    Out of all the bolt on TBI systems out there today the Atomic is the one I like from an engineering/fuel distribution design. Unfortunately there isn't much out there compared to the competitors on how they are working out. Either silence is good news and they work or it just means there aren't many out there. I like the idea of it plugging into a transmission controller too for those going to an overdrive.
    Harlockssx likes this.
  16. gs_jimmy

    gs_jimmy Well-Known Member

    Ken, thanks for letting me know this. I have the HEI, so a clean tach signal is there. But I am still running the external regulated alternator. If I get a bunch a weird stuff, I'll remember this!
  17. gs_jimmy

    gs_jimmy Well-Known Member

    The EFI System just showed up today. Looks really nice, can't wait to get going on the install
    TheSilverBuick likes this.
  18. gs_jimmy

    gs_jimmy Well-Known Member

    Last night I mocked up the TB onto the intake, loosely installed the air cleaner base and did some figuring. Looks like the TB is about the same height as the Holley 750. Both sit on an aluminum adapter plate. So it appears that I should take the width of the plate out of the new foams. Think that this will provide a better seal to the hood. I was running the BBB foams and they got severely distorted (crushed). Any thoughts on that one? I'm also looking into converting to the 100 amp internal regulated alternator to avoid any brown out situations with the EFI.

    This weekend I'm going to see what kind of progress I can make on the install. Wish me luck.

    BTW - my other project is the restoration of War Memorials, specifically M60A3 Main Battle Tanks that are now on display throughout Wisconsin & Minnesota. To date I have done 4 of them. Here is the link:

    These are cosmetic only, the tank can never be functional again.
    Harlockssx likes this.
  19. gs_jimmy

    gs_jimmy Well-Known Member

    Ken, in regard to your comment. I did some looking, appears that the car will be an external reg, 55 amp alternator. So, if I bump up to the 85 amp internal regulated unit (1978 Malibu w/5.7) that should keep me clear of any issues, correct? Car has 1 cig lighter and a small radio. No huge draws on the system. Will be putting an MP3 system in the glove box later this year. Only other draw is the EFI. Battery is new, forward harness was replaced when I did the engine swap (SBB was too short in many places and had been hacked over the years)
  20. Ken Warner

    Ken Warner Stand-up Philosopher

    I would think 85 amps should be up to the task given your details.

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