Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Aftermarket TBI installation

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Mastiff, Dec 24, 2003.

  1. Mastiff

    Mastiff 1/2 ton status Premium Member

    Joined:
    Jul 21, 2002
    Posts:
    2,755
    Likes Received:
    48
    Location:
    Tucson, AZ
    I've been thinking about putting an aftermarket TBI on my 83 blazer, something like a commander 950 from Holley. I notice that my mechanical fuel pump is the kind with a vapor return line on it already, so there are two lines going to/from the gas tank. Is there any reason why I couldn't use this line as the return for the fuel injection system? If I could, it'd make the install a million times easier. Is there an obvious way to tell which line is "from" and which is "to" the gas tank?
     
  2. TopOff

    TopOff 1/2 ton status

    Joined:
    Jan 16, 2002
    Posts:
    1,760
    Likes Received:
    0
    Location:
    Folsom, ca
    I never heard of a mechanical pump with a vapor return line. But I wouldn't know either.

    As long as emissions aren't a problem for you, I would double check with the vapor return line and make sure the line into the tank isn't plugged or otherwise have a charcoal canister on it.

    Ideally the return line will stop at the top of the fuel-tank (as opposed to the bottom and submerged in fuel).

    Also, almost all the TBI and fuel-injected lines require a 3/8" feed line and a 5/16" return line.

    The line sizes are important for proper fuel-pump feeding and fuel-line pressure(s) for the injectors as at all RPM ranges.

    I would still want a vapor line on your gas tank so it doesn't ballon out and cause an explosive situation.

    I am running the Howell-TBI setup. I plumbed in a 5/16" return line. I fabbed a "T" into my overflow tube on the fuel-tank filler. This is probably giving me a little grief but nothing I noticed outside of my fuel-tank filler cap getting more fuel-splashings than normal.

    Good luck.
     
  3. 75-K5

    75-K5 3/4 ton status

    Joined:
    Apr 28, 2002
    Posts:
    5,353
    Likes Received:
    0
    Location:
    Anderson, Indiana
    My mechanical fuel pump has a vapor return line, just FYI /forums/images/graemlins/cool.gif
     
  4. Mastiff

    Mastiff 1/2 ton status Premium Member

    Joined:
    Jul 21, 2002
    Posts:
    2,755
    Likes Received:
    48
    Location:
    Tucson, AZ
    [ QUOTE ]
    My mechanical fuel pump has a vapor return line, just FYI /forums/images/graemlins/cool.gif

    [/ QUOTE ]

    At least I'm not crazy. /forums/images/graemlins/thumb.gif

    I think it's just called a vapor return line, but it actually runs back fuel not needed by the carb. Something about sending the hot fuel back and bring up fesh fuel to prevent vapor lock. I'm not real sure though. That's why I'm asking. It sure seems like it should be good for the EFI.
     
  5. Mastiff

    Mastiff 1/2 ton status Premium Member

    Joined:
    Jul 21, 2002
    Posts:
    2,755
    Likes Received:
    48
    Location:
    Tucson, AZ
    [ QUOTE ]
    Ideally the return line will stop at the top of the fuel-tank (as opposed to the bottom and submerged in fuel).

    [/ QUOTE ]

    Howcome? I've never heard of this. I'm not sure how I could tell anyway.

    [ QUOTE ]
    Also, almost all the TBI and fuel-injected lines require a 3/8" feed line and a 5/16" return line.

    The line sizes are important for proper fuel-pump feeding and fuel-line pressure(s) for the injectors as at all RPM ranges.

    [/ QUOTE ]

    I'll have to check what's already there. It's pretty scary that the whole system could cease functioning because of 1/16" in line size. If it's that critical, I guess I could replace it as far as I could and leave the rest.

    [ QUOTE ]
    I would still want a vapor line on your gas tank so it doesn't ballon out and cause an explosive situation.

    [/ QUOTE ]

    I think I have the vent in addition, this is something different.

    [ QUOTE ]
    I am running the Howell-TBI setup. I plumbed in a 5/16" return line. I fabbed a "T" into my overflow tube on the fuel-tank filler. This is probably giving me a little grief but nothing I noticed outside of my fuel-tank filler cap getting more fuel-splashings than normal.

    [/ QUOTE ]

    I've never heard of that. What is the purpose of the overflow tube?

    How do you like the Howell setup? I looked on their site, but all the kits they listed were for everything but Chevy. Maybe I looked in the wrong place. Do you have a link?

    I liked the idea that the Holley also worked the spark advance through the ESC connector on my distributor. Does the Howell do that? It also uses the knock sensor, which may or may not be a good thing.

    Thanks for the info.
     
  6. SUBFAN

    SUBFAN 1/2 ton status

    Joined:
    Mar 23, 2003
    Posts:
    2,334
    Likes Received:
    0
    Location:
    Davenport, Ia
  7. TopOff

    TopOff 1/2 ton status

    Joined:
    Jan 16, 2002
    Posts:
    1,760
    Likes Received:
    0
    Location:
    Folsom, ca
    The return line should have NO obstructions. If it is in the bottom of the fuel-tank, when the fuel-tank is full it can get excessive pressure. If the return line is obstructed you can get unpredictable results. Primarily you can get a bad idle (more fuel gets returned), a too rich PE (power enrichment). As you try to fix one problem, you may get a bad result of another because of a plugged return line.

    THe feed line needs to b3 3/8" for proper feeding of a V8 and to keep the fuel-pump cool.

    The fuel-injection systems use 5/16" return line and are programmed for that size fuel return and line pressure.
    A 1/16" line is REALLY small for a fuel line. The fuel will not return fast enough and you may burn out the fuel pump, and your TBI will certainly run too rich for excessive fuel pressure at the injectors.

    My overflow tube is really just another smaller line running in parrallel with my fuel-tank filler. It's probably a CA emissions thing.. /forums/images/graemlins/1zhelp.gif

    I am not sure if your stock ESC will work with the Howell computers or not. I think it will with the right harness, I am just not sure.

    I like the howell system. I have had it for over four years with not even a hiccup on any of the systems or components. The reason I really like the Howell setup is because almost all the components can be found at my local auto-parts (Napa, Kragen Pep-boys etc.) as the parts (TPS, O2, MAT, MAP, and temp sensor) are all off of a 87 - 96 chevy truck with TBI.

    The best benefits for me on the Fuel-injection was when I hit a trail with my carb for the weekend I went through a complete tank of gas with my Edelbrock carb. With the fuel-injection I only used a 1/2 tank of gas on the SAME trail and on another weekend! I could hardly beleive it. Idling around all day with Fuel-injection is the way to go vs. CARB.

    Additionally for the trail, I got an extra fuel pump ($100+), extra computer chip ($100), and an extra computer ($150), spare HEI distributor, module, cap, rotor and coil. I could have not gotten an extra computer and chip, but you never know. /forums/images/graemlins/laugh.gif

    However, I never got the chip programmed correctly for my camshaft/engine. I didn't know the specs on my camshaft when I had them program my chips.

    For the money, I would rather have gotten a factory system (for less $) and prgrammed it all myself.



    THere is a great deal of information on diy-efi.org and thirdgen.org. I wasn't aware of these when I build my Howell-TBI for my 383. Of course I get to program another chip for my BBC 402. But I can still use the same Howell/Holley TBI unis (750cfm) for my BBC. /forums/images/graemlins/thumb.gif

    Good luck.
     
  8. Mastiff

    Mastiff 1/2 ton status Premium Member

    Joined:
    Jul 21, 2002
    Posts:
    2,755
    Likes Received:
    48
    Location:
    Tucson, AZ
  9. SUBFAN

    SUBFAN 1/2 ton status

    Joined:
    Mar 23, 2003
    Posts:
    2,334
    Likes Received:
    0
    Location:
    Davenport, Ia
  10. Mastiff

    Mastiff 1/2 ton status Premium Member

    Joined:
    Jul 21, 2002
    Posts:
    2,755
    Likes Received:
    48
    Location:
    Tucson, AZ
    [ QUOTE ]
    That sight lacks information. I would get a factory TBI set up for less money, and modify it from there.

    [/ QUOTE ]

    Pardon my stupidity, but where would I get the factory TBI setup to start with? I wouldn't trust myself to try and harvest one from a salvage yard. I'll look more at the sites you listed, but they don't always make it clear what they are selling exactly.
     

Share This Page