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Vortec heads on a Pre-Vortec block. The definitive guide?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Ryan88Jimmy, Jan 1, 2001.

  1. Ryan88Jimmy

    Ryan88Jimmy Registered Member

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    If this exists where can I find it? [=

    Thinking of rebuilding my 350 this spring and am looking at adding some vortec heads. I am wondering what kind of cam I should use. GM or aftermarket? Also what about intake manifold, I want to keep my tbi setup.
    What kind of computer and tbi mods are required to get everything running smoothly.

    Also anything else you can think of that I missed that would need changing while doing the swap.

    Ryan
     
  2. Gandolf

    Gandolf 1/2 ton status

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    the intake manifold that will work with Vortec heads and Throttle Body Injection was posted a few weeks ago as GM P/N 12496821. The Vortec Exhaust Manifold is GM P/N 1257828 and parts for the EGR modification are: EGR Tube GM P/N 10220275, EGR Fitting GM P/N 12552329 and Vacuum Controlled EGR Valve GM PN 17052693.
    I made notes on these part numbers when they were posted. All of them should be double checked. Someone else will have to help with your other questions. Good Luck.



    '89 K5 Silverado 4" lift w/BFG 33's
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Have to pass emissions? What kind of performance are you looking for? I'm going to use a low lift roller cam (under .450) because of the low end torque it develops, (manual transmission) and the economy, as well as not being as hard on the valve train as higher lift cams are. You will need a new intake of course, Vortec only. Do not mess with drilling the heads, too risky. Edelbrock makes a Performer Vortec that produces power from idle up to about 5500 RPM, and it cost about $100 LESS than GM's intake. Which, by the way, is rumored to be made by Edelbrock anyway. Thats about $155 for the Edelbrock piece. That intake has both square and spread bore bolt patterns. TBI, I guess you won't need the choke, 'cause the performer doesn't have hot air provisions, nor EGR. You will also need centerbolt valve covers, aftermarket decent ones are are as low as $40. I don't think there would need to be any computer mods. The heads flow better at lower lift, and bump the compression up TYPICALLY to about 9.5:1 I believe. I would think that with their combustion chamber design, they will be fine with 87 octane and 9.5:1 compression. So basically, valve covers, intake, and whatever cam you decide. Don't forget though, if you want low end power, a high lift cam and an RPM intake is not the way to go..bigger is not better in this instance. A rolller cam is definitely the way to go if you can afford it, I think yours is alreay a roller if I remember right. If it is, i would stick with it. GM's truck cams were as far as I know, good for low end torque, not upper end. Check my truck specs on my page for the cam I am going to use.

    Dorian
    My K5 and Chev/Olds links: <A target="_blank" HREF=http://yeagerd.home.mindspring.com/index2.html>http://yeagerd.home.mindspring.com/index2.html</A>
     
  4. Nrose07

    Nrose07 1/2 ton status

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    The heads will require a intake that compensates for lack of EGR. The best intake manifold is the Edelbrock RPM. Why the RPM? Because it is the only one with a coolant crossover passage under the carb base. Trust me I tried running this setup without it and there are major drivability problems. For the adapter Holley makes one but all it is is a GM adapter to put TBI's on big blocks. It's cheaper at your local chevy dealer. Don't bother running coolant through the adapter unless you drive in the extreme cold. For the intake just run your coolant through it before the heater core.

    Displacement, cubes, and did you say you drive a riceburner???
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Hmm...never heard of anyone having driveability problems. Is that TPI specific? I know that the problem can exist after freeway driving, as the carb can "ice" up, but that aluminum, theoretically, should conduct heat so well it should still get warm at the carb. (or TBI) Thats theoretical, not fact proven by me. However, the RPM does lose a considerable amount of torque and HP over a stock intake at low RPM's. My Vortec's must be cast FOR aftermarket, I swear there are no EGR ports cast into them. I never checked out older heads, but wouldn't they have a hole right in the center of the intake mating surface that opens into the exhaust ports for the two center pistons? The Vortec's I have do not even have that cut out...the dimple is there, they are not open though.....so the adapter you speak of is a base plate for the TBI, that routes water through it?? Never heard of such an animal, TBI is still newer than what I am dealing with (so far)

    Dorian
    My K5 and Chev/Olds links: <A target="_blank" HREF=http://yeagerd.home.mindspring.com/index2.html>http://yeagerd.home.mindspring.com/index2.html</A>
     
  6. HarryH3

    HarryH3 1 ton status Author

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    I think someone on here mentioned recently that the Vortec heads don't have EGR ports. Instead, the EGR gases are taken from one of the exhaust manifold outlets and routed back through a tube to the intake. This is how the EGR works on my '87 Corvette setup on the engine in my K5. There's a tube that runs from one header tube, up to the EGR valve.

    The Tuned Port Injection (TPI) also runs heated water through the throttle body to prevent icing in cold weather. When it's really cold out and you're running down the highway, all that aluminum is sucking in acres of cold air. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  7. Nrose07

    Nrose07 1/2 ton status

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    Well the injection system I have is TBI, not TPI. Both the adapter plate and Performer RPM intake have passages for coolant, I am only refering to the intake. You "can" route exhaust gases through this passage but I will tell you guys why coolant is far better and more reliable. First and formost reason is your coolant is at a regulated temperture, once warmed up it will keep the intake at a constant temperature. The reason being is the passage will effect intake teperature charge to a greater effect than traditional non-vortec heads with EGR. If you run exhaust gases through your vortec intake the temperatures will be higher than needed and will also increase greatly as engine load increases, thereby increasing the intake charges temperature (which makes it lean and prone to detonating) all during the time that this is most harmful and power robbing. Now if you live in the sourthern states you can probably get away with not heating your intake manifold.
    To address you comment about the efficency of a aluminum intake heating the TBI unit you are backwards in your reasoning. Aluminum more effectivly releases heat. This is one reason they are the only material performance manifolds are made from.
    To clarify your question on the Vortec heads and why we are having this long talk is that in 96' when Chev went into production with the multiport fuel injection they need a better performing head but also one with out EGR. If the intake manifold system is dry (does not contain fuel mixture, just air) there is no reason to heat it. You heat it only to keep the fuel atomized, and since the injectors are at the port openings they did away with EGR. This is the problem we have to over come when converting the L-31 heads to a wet intake system (TBI or carb). This is why we heat it with coolant, to keep that fuel atomized untill it reaches the combustion chamber.
    To finally address the Edelbrock Vortec Performer RPM VS. The Edelbrock Vortec Performer. BESIDES HAVING THE COOLANT CROSSOVER, the RPM does make more power and torque in the whole power band. Read and review a car mag does and you will find this true. That was the "Old School" belief, so I won't take away any points. And if you need I can scan some info for you so you can see the proof.
    Now I hope that answers your questions, and sorry for any spelling errors but I'm not even going to check. Any more questions just let me know. Matt

    Displacement, cubes, and did you say you drive a riceburner???
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    Yes, the release of heat is something I thought about after posting. However, if it releases heat better, does that not indicate better heat transfer properties, which would work either way? I'm no metallurgist (spelling again hehe) but isn't cast iron much denser (heavier weight) which slows heat release AND absorbtion, whereas the aluminum, being less dense, not only releases the heat quicker, but also picks it up? Not arguing, I am curious as to your thoughts on that.

    You are right about the RPM. With underhood clearance being a non issue on the trucks, I'm gonna take the performer back and get the RPM if I can. Check this out: http://www.aros.net/~rbuck/chp/goodwrench3-1.html

    As to running the intake unheated, I would be surprised this can be a problem in most cases. It seems that Fel Pro thought GM was too overzealous in the heat crossovers some of the times, the engine rebuild kits include blockoffs for the crossovers, recommending in most cases to block at least half of the crossover off. Thats exhaust though, not coolant as you recommended. In cold climates, yes, it would be a serious problem I'm sure. Here where it is temperate 365 days a year, I don't think it's much of a concern, after a warmup period, (which my choked vehicles need anyway) I have a feeling I will have no heat/fuel problems. Having to assume once again without knowing of any testing on this specific topic, that you are in a catch 22 with heated intake. Better retained fuel suspension, yet hotter intake air charge, which reduces efficiency. Hence, as you say, unheated TPI intakes. With the RPM intake, vs say the Performer or stock intake, with likely less restriction on the route to the combustion chamber, and less chance for the suspended fuel to condense or puddle, a colder intake would probably be less of a liability. I'm only speaking from my experience with other motors, but I guess I will find out with this motor when it goes together.

    I've got some intake air (air cleaner housing was where this was measured) temperature numbers from a SBC in a Monte Carlo, which would probably be a bit less in a truck due to the size of the engine bay, but if they are anywhere close, it gives you an idea of what you can expect temp wise...115-150 at idle, and on the freeway it's the same. Thats with TPI. With the air being that hot, do you still think fuel atomoization is going to be bad?

    Dorian
    My K5 and Chev/Olds links: <A target="_blank" HREF=http://yeagerd.home.mindspring.com/index2.html>http://yeagerd.home.mindspring.com/index2.html</A>
     
  9. Nrose07

    Nrose07 1/2 ton status

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    Now remember the temperature difference between that exhaust gas and the regulated 195 degree coolant. Even though Fel-Pro includes a small restictor plate for the EGR port that gas that passes through it is superheated. I'll try to find some more info around aluminum vs. cast iron intake for you. Now personally I run the stock intake snorkel on my Blazer because of those under hood temperatures.

    Displacement, cubes, and did you say you drive a riceburner???
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Yes, I read Roe's Q-jet book thoroughly. Up to a 30% power increase by decreasing the intake air temp. Thank goodness for the straight six trucks, all the core supports have the cutouts for dual snorkels, and its real easy to add the second snorkel on the factory air cleaners. I'd love to see some stuff on AL vs cast!

    Dorian
    My K5 and Chev/Olds links: <A target="_blank" HREF=http://yeagerd.home.mindspring.com/index2.html>http://yeagerd.home.mindspring.com/index2.html</A>
     

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