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Thread: Holley TBI adapter

  1. #1
    Fuel Injected! PJG1173's Avatar
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    Holley TBI adapter

    what are you guys thoughts on this adapter? I haven't been too impressed with the way the transdapt 1/4" plate style adapter fit. matter of fact I had to use a spread bore to square bore adapter to make my adapter work where the intake wasn't blocking the throttle blades. is this a better alternative? I can get one of these through amazon for $50.
    http://www.holley.com/17-45.asp

    large17-45v2.jpg
    87 4Runner, 15" spring lift, 3" body, chevy vortec 355, 5.29 gears, 38.5x15.5x15" Boggers, 280hr, 16168625 running $0D
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    EFI GearHead ! EagleMark's Avatar
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    I've liked all the Holley adapters I have used over the 1/4 plate adapters! More money but at least they are machined straight not just a flat piece of metal. The flat 1/4 inch metal adapters I use a gasket and sealer both sides to avoid vacuum leaks.

    Also make sure to mount your TBI with the bolts your going to use and snug them down and make sure none of the bolt protrudes through the adapter, hitting the intake causing it to separate and cause a vacuum leak. Get shorter bolts or use washers.

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    thats what I'm afraid of... I check for vac leaks all the time since it started to warp just from tightening the adapter bolts before I even put the TB on it. yes I also not happy that I had to shave the TB bolts to keep them from hitting the intake. I am not a fan of using rtv on things that come in contact with gas, so i just used the gaskets that came with the adapter.
    87 4Runner, 15" spring lift, 3" body, chevy vortec 355, 5.29 gears, 38.5x15.5x15" Boggers, 280hr, 16168625 running $0D
    93 S10, 12" spring lift, 4.56 gears, F/R lockers, 36x12.5x15 TSL's, long tube headers, 266HR cam, p&p vortec heads, $0D Marine MPFI.
    05 Silverado, 2' lift, 4" exhaust, Bully Dog programmer,

  4. #4
    EFI GearHead ! EagleMark's Avatar
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    Sensor safe gasket sealer both sides of bottom gasket, light coat, wipe clean inside after tightening up, let it dry overnight and it will be fine. Top to TBI I don't like to use sealer but them dam 1/4 plate adapters it's just about mandatory... you'll have way better luck with the Holley.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
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    Thats the adapter I am using. I have not had any problems with it, and it fit like a glove. Its roughly 1/2 inch think if I remember correctly.
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    Yes , the Holley is about 1/2" thick and it is of good quality .

    I bought one a while back , it worked out good .

    For some of the latest ones I have done though , I have just made my own.

    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    2006 Forest river-Sierra 37' 5th wheel
    1999 Astro Van, L31 Vortec , 4x4 conversion
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    1992 454SS "Eh Stock" , Blower & '7427 swap .
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    awsome just what I needed to hear. one is on the way.

    Tom,
    how did you make your own? I have thought about attemting to make one myself. Do you have access to a machine shop, or did you just get creative with some random tools?
    87 4Runner, 15" spring lift, 3" body, chevy vortec 355, 5.29 gears, 38.5x15.5x15" Boggers, 280hr, 16168625 running $0D
    93 S10, 12" spring lift, 4.56 gears, F/R lockers, 36x12.5x15 TSL's, long tube headers, 266HR cam, p&p vortec heads, $0D Marine MPFI.
    05 Silverado, 2' lift, 4" exhaust, Bully Dog programmer,

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    Quote Originally Posted by PJG1173 View Post
    Tom,
    how did you make your own? I have thought about attemting to make one myself. Do you have access to a machine shop, or did you just get creative with some random tools?
    I used a piece of 1/2" Aluminum and patterned it after the Holley piece , My TBI is 2.2" Bore so I would have had to modify the Holley piece anyway , so I just thought it simpler to make my own.

    I made it in a Machine shop I have access to , but I suppose a sawzall / cutoff wheel and a hole saw would produce the same results , a little touch up with a sanding roll and it would be as good as the Holley unit.

    TOM
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    2006 Forest river-Sierra 37' 5th wheel
    1999 Astro Van, L31 Vortec , 4x4 conversion
    1994 Pontiac Sunbird "Work ride"
    1993 K-3500 "Ex-diesel" 454/4L80E - '7427
    1992 454SS "Eh Stock" , Blower & '7427 swap .
    1992 S-10 434 SBC/Tremec - '7427
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 454/700R4
    1977 Olds 98 Regency 403/700R4

  9. #9
    EFI GearHead ! EagleMark's Avatar
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    TBI spacers and adapters

    There are also a couple differant TBI units. one with 2 holes seperated and one that has center open.

    Divided.


    Open


    I beleive the open ones came on Camaro and Caprice. With that in mind and proven results of CFM Tech spacer that has a split opening for divided TBI
    http://marine-performance-parts.com/...eanerstud.aspx

    We used the divided TBI and made the adapter open while also machining the intake for straight shot passages when we made the TBI adapter at the machine shop for my sons 345 IH motor.

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    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
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  10. #10
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    what would the advantage be to the open one?
    87 4Runner, 15" spring lift, 3" body, chevy vortec 355, 5.29 gears, 38.5x15.5x15" Boggers, 280hr, 16168625 running $0D
    93 S10, 12" spring lift, 4.56 gears, F/R lockers, 36x12.5x15 TSL's, long tube headers, 266HR cam, p&p vortec heads, $0D Marine MPFI.
    05 Silverado, 2' lift, 4" exhaust, Bully Dog programmer,

  11. #11
    EFI GearHead ! EagleMark's Avatar
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    Airflow can be used from both sides, balenced. There is a difference in intake manifolds as well between the 2. The IH maifold was also machined/seperated like the adapter to match the intake of open TBI.

    But if you don't have your intake off like we did during a rebuild then just use the CFM adapter with open TBI gasket.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  12. #12
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    Hmm I'll have to look at that. i don't think the divider in my plentum comes all the way up to the top of the flange. the adapter under my tbi adapter is open, so I guess I am already good there. I can't find a good enough pic of the holley adapter to see if it is divided all the way down or not.
    87 4Runner, 15" spring lift, 3" body, chevy vortec 355, 5.29 gears, 38.5x15.5x15" Boggers, 280hr, 16168625 running $0D
    93 S10, 12" spring lift, 4.56 gears, F/R lockers, 36x12.5x15 TSL's, long tube headers, 266HR cam, p&p vortec heads, $0D Marine MPFI.
    05 Silverado, 2' lift, 4" exhaust, Bully Dog programmer,

  13. #13
    EFI GearHead ! EagleMark's Avatar
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    Quote Originally Posted by Nasty-Z View Post
    I used a piece of 1/2" Aluminum and patterned it after the Holley piece , My TBI is 2.2" Bore so I would have had to modify the Holley piece anyway , so I just thought it simpler to make my own.

    TOM
    That adapter above we machined above on the IH is also 1/2 inch aluminum. Even with that stock TBI bolts are to long and hit intake manifold! So you can imagine how bad they are with 1/4 inch. If a guy is unaware and tightens them down he'll bend the adapter causing a severe vacuum leak. If done on an aluminum intake the steel TBI bolt will damage/gouge the intake as well causing a vacuum leak.

    If we had a 10 commandments of EFI one would have to be "Thou shalt not have vacuum leaks" ! If we had a 10 commandments of EFI conversion one would have to be "Thou shalt measure your TBI bolts in adapter" !

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

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    I made it in a Machine shop I have access to , but I suppose a sawzall / cutoff wheel and a hole saw would produce the same results , a little touch up with a sanding roll and it would be as good as the Holley unit.
    That's how I made the adapter for my monoblade TB on the 302 intake and the IAC valve housing on the Toyota engine.

    I also used studs threaded into the adapter plate then ground slightly below flush to prevent any contact with other parts. Makes it nice when setting the TB back on.

  15. #15
    EFI GearHead ! EagleMark's Avatar
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    Quote Originally Posted by 1project2many View Post
    I also used studs threaded into the adapter plate then ground slightly below flush to prevent any contact with other parts. Makes it nice when setting the TB back on.
    Never thought of that? Great idea!

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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