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Thread: vortec heads

  1. #1
    Senior Member EXPERT BUILDER
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    vortec heads

    what kind of rpm's are they good to with screw in studs and the right valve spings and such
    looking to put the on a sbc that will turn 6500-7000 rpm's

  2. #2
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    They will be fine at that, I have a 355 with Vortec heads, hyd. .509-.533 cam and I turn it 6500 on the street. It will go 7000 but the cam don't pull to 7000 on motor. I will run a NOS plate on it every now and then and then buzz it to 7000 with no issues.
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  3. #3
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    Re: vortec heads

    Quote Originally Posted by mrbigtrucks
    what kind of rpm's are they good to with screw in studs and the right valve spings and such
    looking to put the on a sbc that will turn 6500-7000 rpm's
    i hear and read good numbers coming from them heads.... with just a little work :wink:
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  4. #4
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    ok thanks it'l be cheaper for me to run these for now

    max compression should be around 10:1 with iorn heads right?

  5. #5
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    Does not have to be 10.1, mine is 11.5 comp. This engine ran 11.37 in a 3600lbs Chevelle n/a.
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  6. #6
    Senior Member RACING JUNKIE
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    A STOCK vortec head has very impressive low and mid lift flow numbers. Not so much on the high lift numbers. I could be wrong - please correct me if I am - but I was thinking these heads top out on flow at about .550" lift. Great street heads,but if you are looking for a 6-7000 rpm head I would probably shop for something with a bigger runner. Remember,these heads were designed for stock performance,reliability and trucks. They are awesome heads,but not full on race material. Of course if I owned a set I would definitely run them. Anybody know any definite lift/flow numbers on these cast iron wonders?
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  7. #7
    Senior Member RACING JUNKIE
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    this is one of the write ups i had saved when i was reading up on them


    Gary Penn of GM Performance Parts did a writeup a couple of years back about extensive testing GM did on the Vortec heads for performance purposes:

    "Two years ago we undertook an exhaustive (no pun intended) study of the Vortec head in numerous modified states with different valve sizes, throat cuts, valve jobs, port mods, guide mods, etc. We used up about 10 heads, numerous valves, and about $50,000 worth of labor. The study generated 100+ pages of flow and swirl data, which I have at my desk.
    Here is the short version. Out of the box, .480” valve lift, 350-400 HP dependant on the CR, cam, ring seal, oil control, blah, blah, blah.
    More than .480” lift cut the guides down to clear the retainers.
    Straight mill up to .060” safely, .080” with low CR of 10 to 1 or less. 0.100” is living on borrowed time. Always use flat top or dished pistons to enhance flame travel and intake swirl.
    Angle mill up to 1 degree (about .110” off the exhaust side, .000” off intake side) safely for about 12 to 1 CR with flat pistons with little valve relief. Angle mill to 2 degrees (about .200” off exhaust side) if you like to live on the edge, it has been done.
    Larger valves increase flow, chamber mods not needed, trade off between shrouded verses unshrouded valves not worth the decrease in laminar flow and swirl.
    Throat cutting behind larger valves compliments the larger valves. Open the throat to the seat then remove the edge left by the cutter in the port.
    Blend the seats into the chamber, you don't want an edge here to disrupt flow and create turbulence.
    "Bowl blend" and shortened guide in port also improves flow. Taper and blend the iron boss.
    Minumal porting increases flow, too much increase in port size or loss of the benefits of the shape of the stock port will decrease efficiency.
    Vortec heads (and most others) like straight stemmed valves. Undercut valves create unwanted turbulence and a decrease in intake charge velocity (they add volume (slowing the gases) to the overall "port" volume just behind the valve where max velocity is required.)
    Generally speaking, Vortec's stall at between .500” and .550” valve lift. This is where flow actually begins to decrease. But their true strength is low lift flow which gives more area under the total flow curve. And if you think about it how long are your valves at peak lift? They spend much more time at .400” and below, where the Vortec’s outperform most other heads. This combined with high velocity, lack of turbulence and superior combustion chamber design are where the Vortec’s stand out.
    Unported, with all the other tricks in place, the Vortec’s will flow about 235-240 CFM at .500” I and 165-170 cfm at .500” E, on a 4" bore at 28" H2O, with clay radiused port opening. With some careful porting there is another 5-10 CFM or so to be had. But again the low lift numbers are unsurpassed at .100”, .200”, .300”, etc. lift. For example the Vortec’s flow as much air at .400” as .500” and no 23 degree head that I'm aware of can match them at .200”-.300” lift for the combination of flow and swirl. Even the Fast Burn head can't touch them at low lift, it's ports are too big (flow is similar, swirl is less), it does of course out perform them at lift over .500”.
    Unported Vortec’s with the "tricks" can produce 500 HP on well built, high CR, drag race short block. 425-450 HP is more realistic for a killer street engine running on pump gas."
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  8. #8
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    Awesome! Thank you very much Fast75vega! Much appreciated
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  9. #9
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    Quote Originally Posted by olds48
    Awesome! Thank you very much Fast75vega! Much appreciated
    no problem... i got a few other write ups by different shops but this one went in to the most detail and they were saying pretty much the same thing. i was really shocked at how well the heads performed :shock:
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  10. #10

    reduced stems under the valve

    That is the FIRST time I have ever read or heard that valves with undercut stems were a detriment to flow. Or did I read it wrong? If reworking the guide sticking up (shortened guide in port also improves flow. Taper and blend the iron boss helps) it would only seem that narrowing the valve stem would help too. Would this apply to all heads or just the vortex? Wow, some serious change in general thought on this one!! Buddy

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