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Need TBI 350 build advice

Discussion in 'Engine & Performance' started by redneck_reed78, Apr 20, 2020.

  1. redneck_reed78

    redneck_reed78 Full Access Member

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    I have a 1987 GMC R3500. TBI 350, TH400, 4.56 gears. I am looking for more out of the engine. I realize that TBI is not ideal for making more power but I want to keep it as much original as I can as the rest of the truck is basically as it came from factory. I mostly use the truck for pulling trailers. I found a used Edelbrock performer 3704 intake. Looking for suggestions on fuel modifications, which cam to go with that will work with the TBI system, and what kind of machine work could be done to the stock heads on this engine? Not looking to drop $500+ on vortec heads. Any other tips and advice is appreciated. Have been away from this website a few years, glad to see it's still seeing traffic!
     
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  2. AuroraGirl

    AuroraGirl Supporting Member Supporting Member

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    I have no reason other than personal desire to say this

    but

    build a 292
     
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  3. 1987 GMC Jimmy

    1987 GMC Jimmy Automobile Hoarder

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    I would say check out SPR Performance TBI assemblies. They hog out the bore of the base to 46 mm IIRC, do an adjustable regulator, and put heavier injectors. You can get a fresh unit, but it’s cheaper to have your current unit worked. I would say a 454 unit might be worth exploring, but it might be bit much for the 350 cubes. @Daveo91Burb For a fuel pump, you’ll likely need one meeting 1994-95 454 specs. They’re about thirty pounds of pressure, IIRC. Delco, Delphi, Spectra will all likely have their own version of that one. Check Walbro also, but theirs might be double that pressure. For a cam, check out Comp’s computer line in Jegs or directly through Comp. I’d prefer roller in this case, but there are some good hydraulic flat tappets in that family.

    With respect, if fooling with the factory swirl port heads is a compulsory component to all this, I’d say your barking up the wrong tree. Vortec isn’t the end all - be all; you have aftermarket cast iron and aluminum options. I’d even rebuild old Chevy fuelies that have accessory holes before looking twice at the TBI heads. I understand not wanting to have to get the expensive GMPP TBI intake to go with the Vortecs. Way cheaper to go with a pre-87 head design.

    Finally, it’s more than likely you’ll have to reburn the PROM after all that. I’m assuming your intake deletes the EGR, can’t remember which model does and which one keeps it. I would also point you to look at the Holley/Weiand TBI intake variants. They’re aesthetically slick compared to the Eddies that look like the cast mold for the top portion was inspired by a loaf of Texas toast.

    I would say that it wouldn’t be out of the question to make 400 hp/tq. out of a TBI motor following this roadmap or something similar effectively doubling the stock specs. It has its limits that carburetors and MPFI laugh at, but that’s respectable, and TBI has enough of a cult following that these little speed parts are feasible to keep making and developing. I love it. I’d love to build a hot TBI one day.
     
  4. Rusty Nail

    Rusty Nail Whatever!

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    Ya me too.


    I've done the hard part for you @OP. I'm pleased to share this with the world. :D



    Here is a good idea for a TBI 350 I believe it is well thought out because it's my plan.

    Bought OE aluminum L98 heads 87-92 and had em built new valves and old-school 302 "z28" half inch springs...screw in studs with guideplates. Look! Wicked factory heads.
    Add Comp 1.52 self-align roller tips.

    About $800 all in? Thats close but I buy GOOD parts.

    Bought Holley Pro-Jection Intake used and was running a Caprice. $125 maybe. Not much, used.

    Plan includes giving money to these guys:
    Prolly drop $400? there. The fuel pressure regulator spring mod thingy is a must-have.

    https://www.ebay.com/i/201000972987?rt=nc&_trkparms=aid=1110001&algo=SPLICE.SIM&ao=1&asc=225080&meid=d8dbc3e8546242728ecae85a4cb3c105&pid=100694&rk=2&rkt=28&mehot=none&sd=191796802591&itm=201000972987&pmt=0&noa=1&pg=2386202

    AND

    1994 Z-28 LT-1 camshaft.

    Using a 1993 camshaft is possible , but the 1994 camshaft is superior.
    We Lose the cam gear after 94 model GM camshafts scross the board. wont bolt. Must be the 1994 LT1Z28 camshaft to be cool.

    Shops give the lifters and spider away..no need to buy. Donor motor maybe a whole car might show up one day...?

    Gotta have a roller block like in Caprice , Roadmaster , & something else..Camaro/Firebird. Corvette block. :waytogo:

    a roller LO5 engine 87-92.

    Installation of Vortex fuel pump is also possible into TBI fuel tank but unnecessary in this application with the right Throttle Body parts from those Austin dudes.

    Add simple TBI adapter and it will ALL bolt together.
    LT-1 electric fans damn near drop-in bolt together.

    ** prolly best place to start getting more TBI powa. Take the fan off your water pump and buy headers and a new exhaust system.
    Utilize an "H" pipe.

    That's not 400 horsepower but it might be 325 ? with headers..pretty simple and mighty powerful. You could dump money in the short block yeah but again - not necessary. All that stuff in one part might even start. This build is a $1500 aluminum top.
    U said $500 I built a different engine but the same principals apply lol.
    A real simple chip MAYBE...,order online..cheap...I have an ADS Super Chip and wouldnt be too surprised if we put all that together, turned the key and it started. The 113 heads are no EGR passage be aware. The option is 083s or 113s.

    Sure a custom tune Prom eventually) but it might run like that.may be unnecessary too.. The TBI distributor fits/seals and everything..intake is huge IRL...It will bolt together i'm tellin ya. I'd have to try it and know if it would run on the ADS chip.. havent thought about it in awhile..but Lloyd my machinist and I put it together already. .. was lookin at chips and being finished thinkin about it.


    There aint a cooler TBI build out there .
    :cool: If you find one, we're all ears but you aint gonna lol.

    I researched into this to satisfaction and started collecting parts. I pass on 454 TBI.


    Word up.:mad:
    :think:


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    There are two different ProJection intakes and correctly chose #48.
    There was that one edel intake # u got but it's insufficient for this build. Serious shortcomings. I'm biased to Holley but only because it's better.. I dont recall exactly what is was - but you may find some caveat to the manifold you have Sir.

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    TBI especially but (most iron) heads are a waste of time and money.
    I actively seek #083. =BEST RPO iron sbc head ever made.

    #191s? #193? Whatever the #, tbi heads
    Not reasonable. I'd get different ones cuz them aint worth the head gaskets. :(

    s-l400 (15).jpg

    Corvette parts. Tune port parts. Z-28 parts. SBC parts. LT-1 parts. Truck parts. A guy could put all of that together if he was so inclined but it's totally my style. ;)
    :waytogo:
    Hope this helps!
     
    Last edited: Apr 29, 2020
  5. Rusty Nail

    Rusty Nail Whatever!

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  6. redneck_reed78

    redneck_reed78 Full Access Member

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    Awesome I appreciate the feedback from y'all... Little update on this project:

    Snagged a set of nicely rebuilt 96-99 vortec heads from a long time machinist, set up to run up to .500" valve lift (Smoking deal on them!!) and an appropriate Jegs intake manifold and a TBI adapter plate.

    I have been reading up on the Harris TBI site and other forums and I do plan on getting a ported TB as mentioned above and I'll be keeping in mind what I will need to do for more fuel pressure. Will also end up probably having Brian Harris do a chip for me as well since he is such a help I'll give him my business for sure..

    Taking my bottom end assembly to a friend that builds engines as a hobby, and will figure what I need for a rebuild kit; Bore feels really smooth but measuring doesn't lie. If I'm able to do so I'll probably run the stock pistons that are in it (of course new rings, bearings, etc) unless I'm told they will be a big drawback.

    Other than that I just need to figure out what camshaft I want to run, as there is hundreds of options. I really like the Summit K1103 and Brian did tell me that he can make it work with the computer if I go with that... I know very little about cam specs but to me it looks like a good middle ground between a gnarly sounding idle :peace:, and still have enough low down to get the tires roasting and pull a trailer on the stock converter? I just have a hard time doing all this work to a motor and then having it idle smooth and stock like... and of course I'm staying non-roller for now due to buget

    If I can squeeze 300 hp before 5000 rpm and 350 lb ft under 4000 rpm I'd be freaking thrilled; 4.56 gears already in it she should scoot! Let me know what you guys think about that or what you would do for what I have going. Thanks so much!

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    Last edited: Apr 29, 2020
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  7. RecklessWOT

    RecklessWOT Full Access Member

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    Awesome! My 87 'burb has a popped motor and I've been planning on a crate engine, but when I pull it out I'm gonna see if I can rebuild the original engine first depending on what's fucked...

    I too bought 4.56s for it before it died (though a shitty 700R4, we'll see how long that lasts), but I really don't want to get crazy withengine swaps and whatnot and plan to keep it a 350(ish)TBI under the hood. Watching this thread closely, can't wait to see what comes of this!


     
  8. Rusty Nail

    Rusty Nail Whatever!

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    Srsly dude

    LT-1 electric fans damn near drop-in bolt together.
    Electric fans are your friend. Make it happen.

    ** prolly best place to start getting more TBI powa. Take the fan off your water pump,buy headers and a new exhaust system.
    Utilize an "H" pipe.

    Imo improving TBI fuel pressure benefit cannot be understated.

    1. E-fans. LT1 Camaro parts, shroud and all is a good match.
    2. Headers with H pipe
    Mine are 1.5"
    3. Fuel pressure spring

    ^^^ that is how you begin making TBI power

    Then get to axing the swirl port 191/193s
     
    Last edited: Apr 30, 2020
  9. redneck_reed78

    redneck_reed78 Full Access Member

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    @Rusty Nail nail I agree there. I'm definitely trying to make those things happen to not hold it back. I have exhaust taken care off and plan to do just what u mention.
    Might be another month before I get to some of the rest although I understand that it will be a big restrictor without doing them. I'm just on a tight budget due to not working right now, so I have to space out things, can't do it all at once.

    @RecklessWOT I will definitely keep this thread updated for sure! Unless there is major hiccups I should be in the ballpark of $1500 with everything. And Crate motors are good for some application but your looking at easily over $2000 to get something decent power
     
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  10. Rusty Nail

    Rusty Nail Whatever!

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    Hey that's cool man I get it.
    I'm sure it'll be awesome. I know there is alot of good help here. :waytogo:
    Youre in the right place.
     
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  11. redneck_reed78

    redneck_reed78 Full Access Member

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    Brought it to my builder today and he tore it down. He's bringing the block to a shop to clean it up, bore it out and resurface the deck. Going to be about a month before I get it back but I won't forget to update this thread.. Thanks for everyones input so far
     
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  12. 4WDKC

    4WDKC Full Access Member

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    dont do it. stock heads are terrible along with the intake and cam, the engine is out of breath at 3k rpm. i did heads, cam ,intake on the one I had and then still needed to tune it, by the time you get it back you could ls swap it, with an od trans and be able to drive the interstate.
     
  13. RecklessWOT

    RecklessWOT Full Access Member

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    Yeah sure you could LS swap it, but then you have to deal with all the BS that goes into an LS swap. Personally I'd rather spend the extra money and NOT have an LS in my truck. I already have a newer truck with a 6.0, for my square I prefer a simple setup, no need to get crazy with modern engines and have to deal with the nightmare that is OBD2. The LAST thing I would do is put an LS in my square. The sound of the mini starter is enough to turn me off. Then there's the wiring... LS swaps are not for everyone, cost is not the only factor.
     
    Last edited: May 11, 2020
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  14. 4WDKC

    4WDKC Full Access Member

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    while ob2 isnt the best trying to the tbi system that is tbi requires modifying your ecm to use the larger chips or expensive hardware to burn expensive chips that may or not be wiped when you need to re burn them while tuning. He mentioned keeping the tbi system so its not carb swap to make it simple.
     
  15. redneck_reed78

    redneck_reed78 Full Access Member

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    Update on this:
    Just got it back from the shop and started piecing it back together. Quick summary of what I ended up with:
    Vortec heads, Summit K1102 cam, bored w/ new pistons and moly rings,etc. Nothing wild but I'm excited about it.
    I've been working on putting on all the belt drive stuff and stuff on intake.
    Waiting on my throttle body to come back from SPR Performance, it's being rebuilt and bored out. Getting there.

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