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350 TBI Heads, Swap?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by fjleiter, Apr 2, 2004.

  1. fjleiter

    fjleiter 1/2 ton status

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    Have a 1990 K5 with 350 Vin K engine, TBI of course...
    Looks like the motor is going to need a rebuild as well as the heads. Been looking through swap sheet, Ebay etc and looks like I can get rebuilt heads outright for about the same or even less than what it would cost to have mine redone. I know the '90 swirl port heads weren't very well regarded. What would be a good swap in GM heads (not aftermarket) that won't cause problems but will be a good match for this engine. Want to retain the TBI obviously, wouldn't mind early style heads if I can find a TBI intake or adapter that will allow me to run the TBI on a non-tbi intake. Also don't want to screw up compression to bad, I believe the '90 heads are 64cc. Any Ideas???? /forums/images/graemlins/1zhelp.gif
     
  2. Thunder

    Thunder 3/4 ton status

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    Are you going to modify your engine when you rebuild it? Cam intake headers ect?
    Or are you going to leave it stock?
    If you are staying stock. The stock 89 and up heads are really not that bad. They are an early vortec style. Altho they dont flow great for top end they do build very good torque. If you are staying mostly stock those heads are fine for your 350.It was the eariler pre 88-89 heads that were not so great. .

    If you are going to put in a higher performance cam, headers, intake, ect then get some aftermarket heads like World TrokerII centerbolts. They are made to work with TBI. and will give nice power gains. But remember. When you increase the flow you will have to do some mods to the TB to support the higher CFM the engine is capable of. And a new chip will prolly be in order too..Your stock TB only flows about 500 CFM. So you wont see all the power a modified engine is capable of if you try to feed it thru a stock TB

    Edelbrock,turbocity,Cfm-tech all sell adapters to fit a GM TB onto aftermarket square bore intakes. You can put a set of older style 202 heads on and use a cheap aftermarket intake. But you should still mod the TB to flow more. at least put an adjustable fuel pressure regulator on it. To boost the pressure so you dont get a lean condition at WOT.
     
  3. fjleiter

    fjleiter 1/2 ton status

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    Bottom end will be stock, RV style cam, stock exhaust manifold possibly headers into 3" exhaust and high flow cat. If intake is changed it would be to an Edelbrock
    performer type or one of the Holley TBI manifolds. Not going crazy as it still has to pass emissions (all of NY, even the upstate areas is switching to enhanced emissions testing as of June 30th 2004). Just want as much low end grunt as possible.

    [ QUOTE ]
    Are you going to modify your engine when you rebuild it? Cam intake headers ect?
    Or are you going to leave it stock?
    If you are staying stock. The stock 89 and up heads are really not that bad. They are an early vortec style. Altho they dont flow great for top end they do build very good torque. If you are staying mostly stock those heads are fine for your 350.It was the eariler pre 88-89 heads that were not so great. .

    If you are going to put in a higher performance cam, headers, intake, ect then get some aftermarket heads like World TrokerII centerbolts. They are made to work with TBI. and will give nice power gains. But remember. When you increase the flow you will have to do some mods to the TB to support the higher CFM the engine is capable of. And a new chip will prolly be in order too..Your stock TB only flows about 500 CFM. So you wont see all the power a modified engine is capable of if you try to feed it thru a stock TB

    Edelbrock,turbocity,Cfm-tech all sell adapters to fit a GM TB onto aftermarket square bore intakes. You can put a set of older style 202 heads on and use a cheap aftermarket intake. But you should still mod the TB to flow more. at least put an adjustable fuel pressure regulator on it. To boost the pressure so you dont get a lean condition at WOT.

    [/ QUOTE ]
     
  4. 4xcrazy

    4xcrazy 3/4 ton status

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    Just to remind if you didn't know it already, if you put in a cam over stock specs, it needs to be a computer compatible cam,,,they can be pricey too.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Spend some time looking into iron L98 heads.

    Supposed to flow well, BELIEVE they are pretty good performers in general, and should be pretty popular.

    Never researched them much, but I believe they have exhaust crossovers (smog legal in other words, at least visually and functionally) and are also in the '86+ centerbolt valve cover/intake bolt pattern.

    Thunder, if you read this thread again, you say early Vortecs, do they have fastburn style chambers?
     
  6. SUBFAN

    SUBFAN 1/2 ton status

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    [ QUOTE ]

    Thunder, if you read this thread again, you say early Vortecs, do they have fastburn style chambers?

    [/ QUOTE ]

    Curious about this as well.... /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/ears.gif
     
  7. Thunder

    Thunder 3/4 ton status

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    The 89 and up # 14102188 TBI heads have the same 64cc "D" shaped chamber as vortecs. They have the hump in the intake runner for the swirl port thing to help build torque. I think the main diference between the 2 is the angle of the Intake runners. The runners on vortecs are at a better angle and a bit larger so they flow a lot better. Vortec Intakes are also way better than stock TBI
    The TBI heads dont have a fast burn chamber. Neither do the L31 vortecs. Fastburn is a GM performance head thing. GM fast burn vortec heads are diferent than Vortec L31 heads. L31s have the "D" style chamber. The Fastburn chamber is heart shaped.
    The older "crappy" pre 89 TBI heads have a oval shaped 76cc combustion chamber. I think chevy used these heads into the 90s as well because I rebuilt a TBI 350 out of a 91 3/4 ton with these old style heads. Replaced them with 76cc World torquer IIs /forums/images/graemlins/thumb.gif

    Re: the RV cam. Make sure it is compatable with your computer. Crane and Comp cams both make good cams that will run on a stock chip.
    Also wanted to add If emissions are a concern I recomend you go with the Edelbrock package. I put a EDl manifold and their mildest TBI cam in the engine I mentioned above used the stock chip it runs great.
    The truck it went in is a good buddy's of mine it is our wood hauler/work truck beater. It hauls the heavest loads including his fith wheel trailer with ease.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    You are mistaken about the Vortecs. Fastburn means fastburn, Vortec heads utilize fastburn "heart shaped" chambers. D shape is what GM had always used on SBC's prior, AFAIK. Vortec heads are good because GM finally did away with the crappy D shaped combustion chambers, and went with different runners.

    IMHO the chambers are at least half of what make Vortec heads so efficient, since AFR and others can make better flowing heads than vortecs, with "standard" pattern (and smaller) runners.

    If Early TBI heads have intake restriction, no better entry angle for intake charge, and no better chamber than earlier, what exactly does make them better than any previous versions?
    Vortec/fastburn
     
  9. Thunder

    Thunder 3/4 ton status

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    Dorian:
    Yup you are totally right. Vortecs have the heart shaped chambers Sorry to all. My mistake. I got up at 3am drove to Reno NV and back (almost 700 miles) yesterday got home, had a couple of beers. So I wasn't thinking to straight /forums/images/graemlins/woot.gif


    The only real difference in the newer TBI heads is the smaller combustion chamber. Older ones were 76cc. The newer casting has 64cc. because of the raised comp ratio they make a little more power and good torque at low end but they still flow like crap.

    I agree also that the Iron Centerbolt L98s may be a good choice. Would work much better with the upgrades the poster plans to do than any stock TBI heads. Should be able to find a pair for a lot less than Worlds or other aftermarket heads. I think They came on late 80s Camaros and Birds with TPI. Right?
     

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